Water quality control in the humid tropics

IP H I C A B I

WATER QUALITY CO T L

I THE HUMID TROP I S

1

WATER QUALITY CONTROL IN THE HUMID TROPICS

Michel-Alain ROCHE

ORSTOM *

Presented to the International colloquium on HYDROLOGY AND WATERMANAGEMENT STRATEGIES IN THE HUMID TROPICS, Workshop on WATERQUALITY. UNESCO, International Hydrological Program, Townsville,Australia, July 1989.

* Casilla 8714, La Paz, Bolivia

3.8.3.9.3.10.3.11.3 . 12 .

3

CONTENTS

1. ROLE OF SCIENCE AND TECHNICS IN THE WATER QUALITY CONTROL

2. MAJOR WATER QUAL[TY PROBLEMS

3. NATIONAL AND INTER~ATIONAL ASPECTS, AND CO-OPERATION

4. ANALYSIS LABORATORIES

5. GENERAL REFLEXIONS ABOUT STANDARDS

6. EDUCATION, TRAINING, INFORMATION, AND TECHNOLOGY TRANS FER

7. MATHEMATICAL MODELLING AND SOFTWARES ISSUES1. Development of modelling2. Structure of the models3. Role of water quality models in decision-making. Limits4. Sorne examples5. Reflexions on actions6. Direct use 'of hydrodynamic data

8. INVENTORY /DIAGNOSIS OF THE NATIONAL SATUS OF WATER QUALITY,AND EVOLUTION OVER A MID-TERM PERIOD

9. LONG-TERM MONITORING NETWORK AND UP-TO-DATE TECHNICS FOR AWATER QUALITY SURVEY1. Purposes of monitoring water quality2. International experiences for monitoring of water quality3. National and internationaJ compliance with monitoring of

water quaI i ty3.1. Continuous and high funds3.2. Definition of responsible institutions3.3. National co-ordination3.4. Specialization, training3.5. Improvement of national laboratories3.6. Role and action of foreign specialized laboratories3.7. Role and action of United Nations Organizations and

international co-operationConstitution of r0gional groupsChoice of suitable stationsChoice of constituents to he analyzedUse of new technologiesDevelopment and riessimination of PC softwares fordata banks, process and interpretation

10. VECTORS., PARASITES AND PESTICIDES CONTHO!' IN HEALTH ANDAGRICULTURE SECTORS1. General aspects2. Chemistry, remanance and relativ~ toxicity of pesticides

and effects of pesticides in humid tropical

\

4

3. Behavioursystems

4. Factors of transfer of pesticides through thehydrosystems

5. Ways of fighting the agents of tropical diseases andpollution by pesticides : the integrated control

11. MICROORGANISMS, BIODEGRADABILITY AND FEACAL CONTAMINATIONCONTROL, CONCERNING DRINKING AND RECREATIONAL WATERS1. General aspects2. feacal bacterial contamination patterns in the humid

tropics3. Appropriate microbiological indicators of feacal

pollution, used for tests and awareness in the humidtropics

4. Appropriate microbiological water quality standards, andlegislation, for drinking water and recreational water inthe humid tropics

5. Role of microorganisms in the biodegradability of organicmatter, chemical substances and industrial waste

6. Ways of bacterial water pollution control in the humidt

1 •ropl.CS

12~ DOMESTIC AND INDUSTRIAL ORGANIC POLLUTION CONTROL. SEWAGEWASTE WATER AND WASTE DISPOSAL1. Types of urban and industrial pollution2. Causes and aspects of organic pollution3~ Waste and waste disposaI4. Ways of controlling organic pollution

13. INDUSTRIAL MICROTOXICS AND OTHER CHEMICAL CONTROL1. general causes of pollution2. Chemical characteristics3. Behaviour in the aquatic environment4: Standards, analysis and assays5. Ways of controlling industrial microtoxic pollution

5.1. In plant control5.2. Waste water treament5.3. Self-control5.4. Special treatment and security system

6. Ways of natural chemical substances control in drinkingwater

14. INDUSTRIAL THERMIC POLLUTION

15. WATER QUALITY CONTROL RELATED TO LAND MANAGEMENT

_ 16. WATER QUALITY CONTROL RELATED TO WATER MANAGEMENT

5

1. ROLE OF SCIENCE AND TECHNICS IN WATER QUALITY CONTROL

One of the essential chances of sustainabledevelopment is to minimize any adverse impacts on the quality ofthe atmosphere, water and terrestrial environment in general.The environmental unsound degradation of water resourceshas been aggravated by rapid international economic patterns,social and political changes which are causing an exploitinggrowing urban population. In most developing countries, in urbanand also rural areas, water pollution control is still eitherlacking or grossly inadequate although preoccupying in manycases.

It is important to focus on the most important problemsof water quality in the humid tropics, that hydrological sciencesand technics, including chemistry, could contribute to solve.In return, it is also necessary to identify the greatest risksthat water resources management may induce in water qualitychange of hydrosystems in that climatic zone.

Adequate strategies must be pointed out in order to promotea level of preparedness which could help many developingcountries avoid a water quality crisis bi the end of thecentury. Dealing with the problem of ensuring that humid tropicshave a satisfactory, yet minimum in sorne cases. supply of water,mainly in quality than in quantity, is to face the needs of apopulation that does not often have the minimum required, or isseeking improved economic and social conditions. .

the field ofand water

meet the

There is. an urgency to the question of whetherhydrochemistry, hydrology sciences and technology,resources management have the appropriate methods toneeded and rising demands in the humid tropics.

The most useful contribution scientists can offer, is tomake available to the various parties involved ( Agencies,Governments, social groups, etc ... ) the maximum amount ofrelevant -information in a well-digested and constructed manner.50 that, Authorities can make their choice knowingly, onscientific and technical basis and avo;d the postponement ofdecision-making concerning mid and long-term planning and urgentsolutions.

Gaps in information and methodology must be detected. inorder to define the present priority research needs, implementthe existing scientific and technical knowledge ( transfer, co­operation, related social and economical aspects ). setuprecommandations for actions in research, education . and

6

training, and institutional strengthening. Institutional topics,as well as human resources needs, must be analyzed as importantba~ic issues.

These problems can be solved only by a multidisciplinaryapproach, including particularly Hydrobiologists, meanwhileemphasizing the hydrological and chemical aspects.

Water quality problems cannot be solved by an isolatedmean, or for only a determinated sector or region. It is both~

locally and regionally, a global problem that needs to look itscauses, bearings and solutions from all points of view. This doesnot impede the broad prime variation of issues in their acuityfrom one country to another, besides some common andessential problems such as drinking water supply and sanitation ,sewage, and treatment, that nevertheless show different aspectsaccording to local conditions and the developing degree of eachcountry. Therefore, at the begining of such an internationalanalyses, the baselines of the most important topics mustbe presented'extensively, in order to classify them by priority,and to propose strategies for the whole zone. In that sameconception, this report deals with perhaps more specifichydroiogical and hydrochemical issues, such as hydrobiologicalissues, those benifit from being ubicated in a comprehensivecontext. It is shown in what aspects, humid tropics arereally different from the temperate developed zones, wherealready exists a large and useful experience on waterquality control for tropical countries; however this is notal ways applicable. From there also, can be examine accordingto the problems, if high and expensive technology must beapplicable or if objectives would be more reached by "l ow " andappropriate technology, or both together.

2. WATER QUALITY PROBLEMS IN THE HUMID TROPICS

The worrying problems of water quality in the humid tropicsare :

- Aquatic vectors and larvae responsible for water-borneendemics and epizooties, but also pesticides used in vectorcontrol programs and in agriculture.

- Organic urban (feacal) and industrial waste water, andsanitation systems .

. Drinking and recreational water supply in rural and urbanareas.

- Industrial microtoxics (synthetic organic compounds suchas pesticides, heavy metals).

- Change in salt and nutrient cycles and contents, andspreading of water-related diseases, due to land and waterresources management, including new technics in agriculture(deforestation/forestation, new crop strains, fertilizers,

7

reservoir, irrigation, drainage).- Other causes of water pollution that may occur locally,

notably related to injections of hot water or specific compoundsin the receiving medium

The consequences, that are already very serious in somesectors of rural and urban areas, will lead to a more acute waterquality crisis during the next decades in many tropicalcountries, if no efficient and co-ordinated actions are seriouslytaken now.

3. NATIONAL AND INTERNATIONAL INSTITUTIONAL ASPECTS

AND CO-OPERATION

Between the years of 1960-70, most of the tropical countriesbecame aware of the pollution in their environment and . thesignificance of water quality for a growing economy. As pointedout by A. Prost, a sustained development, the promotion ofhealth, and the rational use of water resources are absolutelyinseparable. Inmany of these countries, water quality control,as general water concerns, has been divided among thenumerous/existing national ministeries and services. Links seem difficultbetween national planning, co-ordination services, organismsresponsible for investigation, applied or advanced technology,and the authorities. This pluralism may allow for· morespecialization. However, the lack of an efficient river basinauthority, which is not represented by an adequate nationalinstitution and local and national commtttees (able to make useof a Water Law in which water quality is given priority), leadsto incoherent actions, that are often supported by internationalorganizations. Many national services, expecting a Water Law, aretrying to adapt parts of this law that will concern their areasof water quality. Often, items of the law may interfere or evenbe opposite. This situation hinders rational decision-making,andis sometimes favoured by the fear of some services that measuresagainst pollution may be against production and "low" publictaxes. . 1

Meanwhile, budgets of the different services are q~ite uneven,and the Department of Environment, when this exists, is generallygiven very little.

Often, national laboratories, in relation with the adminis­tration, do not have en9ugh analysis .capacity to make asystematic control of water quality. Nevertheless, this is anindispensable condition to any progress in the general problem(see special paragraph on labor.atory).

Water quality control, in spite of numerous international

8

meetings, has traditionally been considered an internal problem.Today, however, population and industrial growth, as well astechnological specifications, oblige us to a more comprehensiveinternational outlook. Tropical countries may attempt to solvewater quàlity problems by themselves, but this will result inuseless, and unnecessary duplication of work and money for themost important issues.

The experience, gained in developed countries for more than25 years, provides an important technological tool to solve mostof the problems in the humid tropics. There is also a need fortransfer of specifie tropical scientific knowledge and techno­logy between developing tropical countries, because the problemsand the technical adaptations to the zone are similar. It wouldbe important to record the technical adaptations for all types ofwater treatments with its conclusive results, in order to informthe technical services about all the actual possibilities.

Many hydrosystems cross or extend over various humidtropical countries, and are therefore affected by upstream,downstream, or common conditions dealing with water qualitycontrol. Those countries have generally understood theirreciprocal responsibilities and rights, and organizemùltinational commissions to co-ordinate actions. However, thedifferent aspects of managing water resources do not alwaysinclude the problems of water quality. Few,. or none of themultinational structures are able to study and control pollutionefficiently.There are two main deficiencies: first, theneed for international legislation and an inventory of presentpollution, and second, homogeneous standards of maximum load andquality. For instance, the African Convention, established byAUOfor Nature Conservation, could be the frame for such surveyand legislation in the humid tropics of Africa, though variouscountries have not signed it yet.

For instance, themes suchwaterbodies, groundwater pollutionrials could be carried out in theprograms.

as eutrophication in warmby nutrients or toxic mate­framework of international

Sorne countries already have structures and laboratoriesthat are able to conduct inventories and a water quality controlmonitoring network but many do not. International Programs canoffer them a realistic way of participating as well as profitingfrom international networks of analyses and other technicalpossibilities. (Global Environmental Monitoring SystemGEMS/WATER, 1974 -IGBP, 1988, Geosphere-Biosphere).

andmost

softwares,of the

Exchange of data base and interpretationmathematical models acting on PC, are also oneimportant issues.

Interlaboratory calibr.ation of the analyses is necessaryto standardize the resultsand their utmost interpretations.

9

Education and training must rely on international co­operation. Developed countries, that have a great deal of expe­rience in water quality control, can play a great role in thisarea.

4. LABORATORY ANALYSES

Many countries do not have analytic facilities to make iso­lated or routine analysis of water samples, including physical,chemical, bacteriological and biological standards. Sometimes,all these facilities exist in one country, but are dispersed,therefore making the co-ordination for an isolated analysis or aproject study very difficult. It also occurs that hightechnological instruments are available in one 1aboratory , butare not used because of technical details, lack of a specializedoperator or definition of research themes.

Therefore, for a rational organization dealing with watercontrol, it seems imperative that every humid tropics countryholds of at least one functional laboratory able to realizecomplete analysis, including all main water quality standards.

The basic appropriate needs are- infrastructure,- equipment,- specialized staff,- financial means for salaries and functioning; part of the funds

could come from the sale of the analysis.

Detailed lists of precise and optimal needs can bepresented.

This kind of laboratory must :- be regularly entitled to receive certificates of ability in

analytic measurements. This means a national and internationalsystem of checking samples for interlaboratory calibration ofmethods and instruments.

- be recognized as an official entity of the water qualitycontrol system,

- be thoroughly connected with all the authorities in its field.It may be directly integrated in the service of a Ministry (ofHealth, for instance), or indirectly through municipal ordepartmental authorities responsible for local sanitation, ordepend of the University.

There is an urge of interest in developing once, again therole of the University Research Institutes that have analysislaboratories. These institutes generally have the adequateability to rigorously put to use and adapt specific techniquesand methodologies dealing with environment quality. They must not

10

only make routine analysis, but also investigate specific'environmental 'problems which occur from time to time, as well ason great national projects, or treatment technologies, forinstance. It seems important that the analysis be realized withinthe proper Institutes or associated institutes that carry out theresearch study. Involvement of the University can provide theappropriate scale for the necessary global view of the problems,the multidisciplinary basic conception, and means. Moreover, alarger participation of this institution in water quality controlwould reflect directly on educational actions, which constitutean aspect of major importance in the fight against pollution.

Regional and international exchange of knowlegde andtechnology in the management of laboratories is one of the mosturgent concerns about water quality control.

International organizations and other supporting bodiesshould give more assistance to humid tropical countries, onrequest and if appropriate by providing equipment, funds,training, manpower and expertise missions.

5. GENERALITY ABOUT STANDARDS

Water quality control must be based on standards for inputand output water.

Threshold contents have been deduced from the knowledgeabout the effects of chemical constituents in animals or men, butalso from empirical methods. The toxic effects of specificpollutants have not been studied much in the humid tropics,meanwhile their proliferation is increasing. Therefore, like inother areas, it is necessary to carry out such investigations inorder to obtain precise and useful threshold standards. In thepresent state of knowledge, it is possible to think thatcarcinogenic or mutagenic substances and heavy metal componentscould take specific forms in that zone.

Local .conditions must also be taken into account tomodulate standards: higher temperature and.solar radiations,lower oxygen contents, frequency of toxic discharges, type andamount of accumulation at various levels of the sediments andthe tropical biotope, higher discharge, etc ...

The most important standards for man, deal with drinkingwater and recreational water, taking into account that qualitydepends in the observance of the standards for waste water.

The standards for drinking water must guarantee a harmlessconsumption. WHO has published standards which are the base fordrinking water quality control in many countries (EFP/82.39,

11

EFP/83.58, Guide for drinking water quality -1986-), althoughothers often have adapted their own standards.

Natural water, with its higher level of purity generallyseems suitable, butis it favorable to health and not harmful inthe tropics? On the other hand, general standards mighteventually be ajusted in relation to the quantity of waterabsorbed, which is (a little) higher in the humid tropics than inthe temperate zones.

It seems, that an eventual modification of standards wouldneed particular and difficult studies. Meanwhile, an inventoryof the standards used in all the countries of the humid tropics,and the justification of their values, could be of the highest·interest.

The problem about the indicators of feacal contaminationwill be dealt with in the chapter about drinking water supply.

~fter Kilani (1989), from the point of view of thedeveloping nations, the most significant shortcoming is thelack of flexibility of the standards. Many governmentsfind themselves investing large sums of money in projectsdesigned to attain high standards in communities where muchlower quality standards may be required:- Thus, unattainabilityof standards could be partially responsible for the failure ofmost water supply projects.

6. EDUCATION AND TRAINING

1. Education ..

Education, in the framework of an integrated water qualitycontrol, is one of the most important ways to develop in thehumid tropics. Only the full awareness by the individual, fromthe earnest age, of one's own weight in the fight for a' safeenvironment, can give satisfactory results at term.

Consequently, aquatic environment control should be primeconcern in natural sciences educational programs in elementaryand high schools, where it could easily replace sorne issueswithout damage. The education has to be completed by television(cartoons, vulgarization), newspapers (comic books), conferences,expositions, posters, stamps, contests/primes for children andadults.

Simultaneously informing the media as well as providingguidelines and facilities for the corresponding actions shouldbe' the responsability of the services of water quality control.Likewise, pedagogical an~ informatlve conferences would

12

necesssri1y have to be given to professors.

In relation, it could a1so be the UNESCO's role to organizecontests for aquatic medium protection; with prizes for pupils,investigators, laboratories, industrials, agricultors, and towns.

2. Training

Training wou1d be the concern of universities, specializedschools and services. It would be necessary to make a census ofthe existing training structures in every country, not only inthe humid tropics, and in p~rticular those that could receivetemporary foreigners. Also, each humid tropical country mustestab1ish a diagnosis and foresee the needs of scientifical,technica1 and administrative staff in order to insure essentialeducation and training:

- Hydrologists, specialists in hydrodynamics, waterqua1ity, modelling, with comp1ementary capacitation. Bio10gistsand hydrobio10gists. Statisticians.

. - Engineers and technicians in water and waste waternetworks, treatment.

- Documentarists, reporters.

These issues have re1ated impacts within each of theresource deve10pment areas and need to be adressed as such.

3. Information

Often national works and a fortiori foreign works are notavailab1e at the right time, or not known by who begins similarstudies.

There is a need for most tropical countries to hold and todisseminate a national and international bibliographic index onecology, hydroeco10gy, hydrochemistry and water quality control,in order to faci1itate an integrated approach in managementdesign. This indispensible tool must be on microcomputer,with a11 investigation facilities .

Particularly, the circulation of information and reportsconcerning UNESCO / Conaphi about the works realized in theframework of the· the new activities of the PHI, could concern theexamp1es mentioned in the other chapters such as values ofstandards of operational mode1s.

space andis possibledilution ofability of

the risks of

13

7. WATER QUALITY MODELLING AND HYDRODYNAMICS

USEFUL\FOR DECISION-MAKING

1. Oevelopment Qf modell;ng

The evolution of suspended and dissolved components in spaceand time depends mainly upon the evolution of the vector, i.e.the water dynamics. Water is an indispensable mineral to life, itirrigates ecosytems, and plays a role in the landscape similar toblood or sap in living organisms.

Many previous studies on water quality have not ponderedsufficiently on the vector dynamics. Such a lack limitsconclusions, notably prospectives and decision-making. However,nowadays,' there has been such a prompt development ofmathemat i ca l .mode 11 i ng of water qua 1i ty that i t i s al mostimperative to be acquainted with it in order to adapt ~o humidtropical conditions, if necessary.

In the last years, various symposiums and workshops havebeen held on this subject, and more are foreseen during the nexttwo years, often sponsored by the UNESCO (Stuttgart, April 1989;Tunis, May 1990; Geesthacht, Juné 1990; The Hague, September1990). Various books have recently been published on waterquality modelling (James A., 1984; Orlot G.T., 1986; TrudgillS . T ., 1986).

2. Strycture Qf ~ models

Those models apply to unitary or complex hydrosystems, suchas streams, lakes, lagoons, reservoirs, urban watersheds, ground­water. and estuaries. They couple a chemical model to ahydrological model of transport. Physico-chemical phenomena canbe taken into account in: (1) substance production functions(ex. the sediment production by erosion, nitrogen productionin the root hdrizon), (2) physical or geochemical sedimentation(soil, streams, reservoirs), (3) physico-chemical, microbiologi­cal or biochemical trapping and transformation (interactions withthe bottoms, flora, fauna), (4) concentration by evaporation, anddilution by rainfall. In some or all the pathways of the models,the transported components can also be considered with fixedcontents, according to conservative chemical processes.

3. ~~ l;mits Qi water ayal;ty models in decjsjon mak;ng.

By the simulation of the process evolution intime, and with some purely hydrological results, itto predict downstream from a disposal, that is : thea product, the self-purification capacities, thesedimentation of dissolved and suspended substances,

\The Vollenweider-OECD model (Vollenwieder and Kerkes,

1982), has been used to predict the phosphorus concentration oflake from the inputs and the eutrophication risks.

14

eutrophication or concentration (salinization, nutrients, pesti­cides, etc).

The adaptation of models to humid tropical conditions mustbe realized through the calibration of the different functionsand the reliability of the results. Technology to evaluate theconfidence levels of predictions must be developed in order toaccount for uncertainties in the decision-making. Variousspecifie chemical and biochemical processes must be modelled toaddress the results in the best way.

The effects of irrigation and massive use of fertilizersconstitute an area of application of the models, particularly forgroundwater. Likewise, in urban and industrial media, they applyto(1) dimensioning and functioning of drainage networks of rainand waste water, according to the organic load (02, BaD,COD, ... ), notably for polluted urban flood storms, (2)evaluating the effects of purification systems, optimizing thefuntioning of treatment stations or disposal control.

4. ~ examoles

Temperature is one of the parameters that differs the mostbetween temperate and tropical zones. It has a direct influenceon physical, chemical and biological properties of an aquaticmedium. A water temperature model, in the framework of a waterquality modelling in natural or made-up conditions (Morin et al.,1983-1985), has been coupled to the conceptual hydrological modelCEQUEAU (Girard et al., 1972; Morin et al., 1981).

Girard (1988) presented a joint modelling of water andnitrogen in a groundwater system where the different yields ofnitrogen are developed in a production module (rainfall,fertilizers, animal deposition); The author mentions that themain problem of the modelling is to determine the nitrogen flowfrom the non-saturated root zone to the aquifer. The model usedagricultural parameters such as the type of crops, the spreadeddosis of the fertilizers, the chemistry of the products, so thatit is possible to simulate preventive decision-making for thedecrease of the pol lutant, or curative measures based on thedilution of a contaminated aquifer by injection of clean water.Some biochemical processes and surface transport need to beincluded in the modelling, in order to improve the results. Like­wise, the author insists on the need for better agriculturaldata (annual crop maps).

In the PHICAB project, Benavidez (1988) applied aconceptual model (HYMO 10) to predict the effect of soilmanagement on soil ero~ion and sediment transport in a watershedof the Andean Amazon of Bolivia.

15

The estuarine water quality modelling meritsattention because of very marked hydrodynamics anddissolved and suspended contents, that generallyinteresting results (Symposium of Geetshacht, 1990).

a specialchanges of

lead to

Modelling of waste water sewage and disposal, urban stormfloods, and/economical aspects of water quality control must alsobe examined (Servat, 1984).

5. Reflexions on actions

Those references should not be exhaustive, since it is anarea of intense present activity specifically concerning waterquality. In order to be able to use an efficient specific toolfor water quality decision-making in the humid tropics, it wouldbe extremely useful 40 dispose of a complete and detailed list ofreferences of functioning models and books, -and that all thisinformation be communicated to the PHI National Committees. Themost adequate models could be tested and adapted to local·problems. Of course, specific modelling must also be developedfor very specific cases~

The diversity of the areas of application, in order tohold a functionning "national whole model" , would require studies

'of models for each type of sectors, hydrosystems or associatedhydrosystems.

Modelling must associate telemetry technics for a betterregionalization.

Collection of data related to the economy is ve~y usefulfor the results given by the models.

6. Direct use of hydrodynamic data

To perform, water quality modelling needs or directlyprovides, partial results on water dynamics, that can be usedfor some evaluations or even be associated with the contents,for simple evaluations, such as transfer or residence times forinstance. With or without complete modelling, it is then usefulto carry out measurements to obtain the following evaluations :

- Rainfall : quantity, intensity.- Trajectories and magnitudes of the horizontal, vertical and

transversal movements, stratification, mixing, etc ...- Transit velocities, measured by natural tracing (dissolved

constituents, salinity, isotopes), artificial tracing(radioelements, colorants, float-balls, chemicals, etc ... ) orby other ,appropiated hydrometrical methods. These datagenerally go along with the evaluation of discharges, volumesand transfer times.

- Turn-over and mean age of the water.

thaton an

16

- Infiltration, resurgence, and evapotranspiration,represent other terms of the water balance, establishedappropriate time step for the specific case~.

One should notice that research on water dynamics oftenuses physico-chemical characteristics, like qualitative orquantitative tracing. However, studies on hydrochemicalprocesses benefit in return from the so-obtained knowledge onthe vector.

8. INVENTORY AND DIAGNOSIS OF THE PRESENT NATIONAL STATUS OF

WATER QUALITY, AND EVOLUTION OVER A MID-TERM PERIOD

1. It is a matter of urgency, for most countries in the humidtropics, and globally in that zone, to establish a scientificand technically detailed inventory and diagnosis of waterquality, which would allow the availability of a national andgeneral overview of the present situation, and to learn moreabout its evolution over a mid-term period, by a second studyphase (five years later for instance).

2. Sorne synthetic works dealing with hydrosystems of regionswhich include humid tropics countries are available. Amongthese publications we can mention for example : the ecologyand utilization of African inland water (Ed. Symoens J.J.,1981), draft review of the state of aquatic pollution of EastAfrican inland waters (Alabaster J.S., 1981); Tracageisotopique et salin des eaux du systeme hydrologique du LacTchad (Roche M.A. ,1973,1980); La pollution des eaux conti­nentales africaines (Dejoux C., 1988), etc ...

3. In all countries, valuable studies on global environment, orwater chemistry and quality of one or several hydrosystems,already exist (example: Bolivia, Chad). However,.projectshave generally not been exhaustive enough to draw a completepicture of the national aquatic environment (water,fauna,flora). Specially, the presented characteristics (oftenmajor ions only) were used to explain natural phenomena,without concluding on pollution aspects, because much conta­m"ination was not visible. Only the most serious problems havebeen taken into consideration.

4. It occurs that incomplete knowledge onquality, is sometimes due to thedetermination in the realization of adiagnosis, besides the lack of necessary

the level of waterlack of nationalgeneral inventory-

organization. : ../ .

1

5. It is necessary to diagnose the present level of pollution in

17

all the different hydrosystems that are impacted by manactivities, within each large basin, in order to know themagnitude of the actual problem, and therefore have a base ofreferences that permits the detection of, future evolution.A second state study would show the trends versus the originstate. Such a reconnaissance survey of water quality in thehumid tropics is the basis of a water quality policy, bycomparison of present and future characteristics. Waterquality problems being classified, urgent national andinternational planning and decision-making could rapidlyoccur in case of emergency.

6. In sorne humid tropical countries, unpolluted or almostunimpacted hydrosystems can still be found. Their study isurgent, because they can bring reference criteria innumerous scientific areas (for instance chemical andbiological processes, steady-states, etc ... ) about theoriginal states of sorne types of aquatic ecosystems thatwill not exist within a few years. It is important tocharacterize representative hydrosystems to learn how naturalsystems function and to ensure . them the highest level ofprotection, as baselines and reference areas over a longperiod (National Parks).

7. Lack of knowledge would be identified in space and time.Then, among the practical recommendations of such aninventory-diagnosis, the necessary complementary studiesabout water chemistry, water quality and other aspectsdealing with water quality control as a whole cou1d bedefined.

8. A detailed inventory 'and diagnos;s, in which multidiscipli­nary skills would have to be involved, could be the beginning(for the least advanced countries in this area) or animprovement (for the others) of a national . functionalorganization and the necessary co-ordination of institu­tional structures.

Moreover, for many countries, such a project study would be auseful experience in the creation of a water quality· databank, and the processing of standards and results at anational level.

9. Global knowledge about precise national situations in a11the humid tropical countries would help detect common orsimilar concerns, that could then be properly addressed byinternational or bilateral co-operation actions.

10. To avoid the heterogeneity mentioneo in previouspublications, a working plan could be proposed as a guidelineto lead project studies on inventories and diagnosis ina homogenous manner in each country, and realize a synthesisfor the humid tropics. These studies would obviously takeinto account specific national conditions that might coerceto modify or end parts of them.

The. studiesthat would

18

would be made for large watersheds, a divisioncorrespond to local institutional structures.

Explanations would include charts of the numerousorganizations, diagrams, plans and maps, including referencesto social, economic and manpower aspects.

a. Preliminaries

- Previous works and publications about water chemistry and waterquality control.

- National and international divisions of watersheds andhydrosystems (water courses, aquifers, lakes, estuaries,etc ... ) .

- Physical characteristics, biogeodynamics, geology, hydrodynamiccharacteristics of soil, ground and bottoms.

- Items of pollution tied to men activities : population (cities,villages, ... ), agriculture, industry, vectorial control.

- Climate, especially rainfall, radiation, temperature, andevaporation.

- General hydrology : water resources, water balance and regime,extreme values (low waters, floods), physical aspects,existing models. Regime of sediment loads.

- Water dynamics (with or without mathematical models).- Ge~eral biological aspects (flora and fauna).

b. Institutional structuresordination laboratories.co-operation).

concerned institutions, co­Available means (laws, equipments,

c. Methodology used for the study.Recollection of information.

- Choice of standards versus classification of water uses (input,output), classification of water uses.

- Basic data banks. Softwares for data banks.- Analyses methods and laboratories.- Softwares for interpretation and water quality modelling.

d. Natural and modified characteristics of water quality inhydrosystems.

Present state of the hydrosystems and the entire basin, aboutabiotic and biotic characteristics. Present steady-states.Abiotic (sediments) and biotic (plants, animals) indicators ofpollution. Effects, consequences of pollution. Water­associated diseases (bacteria, vectors, ... ).Consequences of short- and long-term pollution on health,domestic and wild animals, cattle, and any form of life.Experiences with lethal effects. Accidents.

e. Available types of water quality, and respective resources,according to sectorial uses. Seasonal variability withdischarges.

f. Needed types (and respective amounts)of water quality, accord-

19

ing to sectorial uses. Adequation availability/needs. Existingand proposed water supply systems and treatments for drinking,agriculture (irrigation, drinking water for cattle), industry,nav'igation, etc ... Perspectives (2000 ?).

g. Origin~ situation, chemistry, flow of punctual or non-punctualpollution for any sector (including vectorial control).Systematic detection of secondary sources. Vast developmentprojects having an impact on the hydrosphere (ProgramLG.B.P.).

h. Present systems and technologies for treatment of pollutionsources, by sector (waste water, industry, etc ... ). Recyclingwaste. In-plant control. Security systems. Control oftreatment programs by pesticides. Needs, perspectives andpropositions.

i. Specific concerns.

j. General classification of concerns and general p~rspectives.

Proposal of solutions concerriing :- Institutions: Structures, specialized man-power, laborato­

ries, economic aspects, co-ordination, co-operation.- Complementary studies to complete' the inventory-diagnosis.- Actions and means 0 eliminating or reducing existing

pollution, . avoiding predictable pollution and leading"catastrophe" operations, continuing long-term observationsand control of all types of pollution.

- Economic estimates cost of preventive or curativemeasures/cost of damage.

- Social implication.

k. Conclusions. Needs. Recommandations.

1. References: A national bibliographic reference list must beestablished by each country for projects dealing with waterquality. Reference of studies on water dynamics, aquaticorassociated fauna and.flora, urbanization, industrialization,agronomy practices, and all matters related to waterquality,would also be included. The mostimportant results would besummarized in the national study.

9. WATER QUALITY MONITORING NETWORK

1. Purposes of monitor"ing water guality

Parallel to inventories or diagnosis, periodically carriedout every five or ten years in order to gain a synopticstatus of the situation, it seems indispensable to obtain dailyto monthly data from a water quality network, in order to:

20,

- Assure cont;nuous1y that water qua1ity is appropriate forthe needed uses.A1though a 1itt1e different in design, a warning system ;sbased a1so in monitoring~ spec;fica11y in rea1 time. More or1ess rapid1y, both systems a110w the identification of thenature and source of contaminants and immediate decision-makingto face it, particu1ar1y to avoid an eventua1 accident orcatastrophe before a spatial extension. •

- Detect the 10ng-term trends of water qua1ity, from local toglobal 1eve1s, by acquisition and interpretation· of longtemporal series of ana1ysis data, inc1uding extreme valuesand short-term shock 10ads of po11utants; improve the ca1cu1a­tion of matter balances. Such a data base is essentia1 forcomparison purposes, and especia11y to investigate thepotentia1 impacts 1ikè the greenhouse effect or dep1ation .ofozone, on water resources, inc1uding water qua1ity.

- Improve mathematica1 water qua1ity mode1s, and theiradjustement with longer series of measurements, which permitthe identification of 10ng-term trends in water qua1ity. Feedprospective scenarii for the assessment and planning of theresources, long-range forecasts, and rea1 time operationa1warning protoco1s. The obtained data are the background of a

~ regiora1 understanding.

2. International experiences for monitoring of water gua1ity

Various 10ng-term networks have been proposed or set up tomonitor water qua1ity 10ca11y.

- "The Global Environmenta1 Monitoring System" (GEMS) has beenorganized by a group of international Organ;zations (UNESCO,WHO, WMO, UNEP) to create a wor1d environment program, basedon a wor1d monitoring network, since 1974. The GEMS/WATER dea1swith the water qua1ity monitoring system. The physico-chemica1and bio10gica1 ana1ysis data are stored in a Reference Centerwhere period;c interpretations are made. If desired, nationalparticipation can be 1imited to samp1ing and ana1ysis. Calibra­tion of methods and resu1ts of ana1ysis can be he1ped by thereference 1aboratory, in particu1ar by sending witness solu­tions. Not.a11 countries participate in the GEMS/WATER, thoughcontacts are being made for a broader international participa­tion. Such a program will be meaningfu1 on1y on a 10ng-termperiod and with a sufficient density of stations. However, somecountries can a1ready see fluctuations.

- Among various wor1d programmes inc1uding a water qua1itYnetwork, the recent "International Geosphere-BiosphereProgramme (IGBP)" shou1d be mentioned. Its goal is to deve10pa co-ordinated action to describe and understand the physica1,chemica1 and bio10gica1 processes which regu1ate the who1eenvironmenta1 conditions on Earth by their interferences; andto predict how human activities cou1d disrupt this system.

- At a regiona1 1eve1, the fo110wing actions can be mentioned asexamp1es, among many others ( Dejoux, 1981):

21

* Commission of Lake Chad Basin (CBLT)* Committee for Continental African Fisheries, 1972 (CPCA)*-East Environmental Pollution Research Committe (EEPRC)* East African Federal Fisheries Organization'(EAFFRO)

- In South America, the PHICAB Project (Climatological andHydrological Project of Bolivia, ORSTOM - CONAPHI -IHHSENAMHI), assures for sorne years the monitoring of waterquantity and quality (salinity, major ions) in the Amazon Basinof Bolivia, and has carried out a reconnaissance of waterquality in the entire Highlands of the Andes,in the lakeTiticaca and Poopo Basins (Roche et al. 1986,1987; Guyot etal., 1987,1989).

3. National and international compliances ~ monitoring ofwater guality

To be realistic, the proper functioning of a long-termwater quality network appears to be very difficult, especially indeveloping countries. Many factors, essentially the same onesthat have been previously mentioned for a water qualityinventory-diagnosis, are even more serious for the proper

'management of a monitoring network, because of the continuousspecifications of the programs and the high needed means forinstruments, installation, and maintenance. The economic crisisof these last years have weakened the quality and density of thenetworks, while the delays in the collection and processing ofthe data are getting longer and longer. National hydrologicalorganizations are having more and more difficultyin performingproperly the management of their networks.

Possibilities of rehabilitating the density and theefficient functioning of water quality networks must be exploredurgently :

3 .1., Continuous and high funds. Both national and internationalcompliances are necessary and need to be improved. Countriesmust search integration of their own actions with internationalprogrammes, in order to increase their possibilities. The abilityof. developing nations to support the funds of the monitoring ofwater quality and quantity networks as well as the ability and.

·reasons of developed nations to share the cost, is an important"issue. As a reference, one can mention the large participation ofthe French Instititute of the Scientific Research for' theDevelopment in Co-operation (ORSTOM) in the monitoring ofnational hydrometrical" networks, often accompanied ofhydrochemical studies, in West and Central Africa from the 1940'sand in the 80's in the Bolivian and Brazilian Amazon.ln past~ears, remote sensing hydrometric stations have beeninstalled inWest and Central Africa and Brazil. Recently, the EEC partlyfunded the telemetry equipment. Canada mentions also its co­operation in monitoring networks. The WMO and WHO support underspecific hydrometric monitoring projects.

3.2. Definjtion of responsible institutions, in particular for

22

water analysis laboratories.

3.3.National co-ordination and responsibility between and withininstitutions (for instance, the HYWA Organisation; paragraph3.11 ).Circulation of information.

3.4. Specialization. trainings, staff increases for field work(measurements and sampling), laboratory and office.

3.5. Imorovement of national laboratory, equipmenttioning.

and func-

3.6. Role and action of foreign specialized laboratories andcenter. Interlaboratory calibration and special analysis.

3.7. Role and action of United Nations Organizations andinternational co-operation in the organization, management, andmaintenance of water quality networks. UNESCO can play animportant role in some issues. In particular, there is a need toensure circulation of information, such as protocols, softwares,results and publication of studies, ...

3.8. Constitution Qi regional groups, committees or commissionsto carry out actions in large basins or groups of similar smallbasins (Amazon, Congo, Nile ... , small coastal tropical basins ofAsia, etc ... ). Such organization for instance is indispensablefor the telemetry system (HYWA Organisation ).

3.9 Choice Qfsuitable stations (minimum and satisfactorydensity and representativity) , according to the results ofthe previous inventory-diagnosis study and previous experiences.Network design, of water quality monitoring sites must ensurethe data being collected are adequate for the intended purposeand the establishment of the costs, benefits and economic aspectsof water quality collection. In fact,' the difficulty ofmonitoring water quality is due to the proliferation of man-madechemical compounds. Can observation networks and usual analisiscontrol systems, truly detect the existence of all these harmfull

:Substances in the hydrosystems? It seems necessary to detectthem at their potential industrial sources, and then to controlthèm downstream, knowing that they find their way by complexpatterns into water bodies, and are either removed partially bytreatments or natural processes, or remain and accumulate. Oneexample is the groundwater survey of a factory by a piezometernetwork, in order to control upstream risk of pol lutantinfiltration.

Due to maintenance, measurements and exploitation of thedata, most of the water quality stations must be coupled withhydrometric stations.

3.10 Choice of constituentsfrequency of analysis. It isaccount the new technologieswhat pollutants need to be

to be anal yzed, number andnecessary to decide, taking intoof measurement and transmission,monitored, why .~nd· how. The

23

specification of the objectives he1ps determine the preClSlon andaccuraçy to be attainèd, considering the cost-effectiveness ofthe operation and theneed to save money.

3.11. Use of new technologies. Water qua1ity monitoring systemsfor continuous and long-term control in rea1 time, and theprevention, have to be used a10ng with remote sensing technics(te1emetry by satellite, phone, radio, overa11 by sate11ite)~

Insu1ated large areas without observers in the humid tropics arethe concerns particu1ar1y (Africa, Amazon, Bor?eo, ... ).

Sensors responding to requested water qua1ity standardsmust continue being designed, improved, tested, bui1t, and wide1ydisseminated. Those faci1ities seem to be the on1y near poss'ibi~

litY to improve the 1ack of or fa1se data of the 80's and thecurrent evo1utive attitude of the observers.

The experience acquired by the Hydro1ogica1 Watch Organisa­tion (HYWA), with the participation of ORSTOM in West and CentralAfrica, under international co-ordination, permits data collec­tion and dissemination from a se1ected number of Hydro10gica1stations (Pouyaud et al., 1987). This is just the beginning ofwhat must be done in various areas, for water qua1ity control,pairing hydrometric and qua1ity measurements (Bader J.C. etal., 1987; Gautier et a1.,1987; Gioda A. et al., 1988; Le BarbeL. et al. 1987 ). Satellite te1emetry is a1ready widespread inthe region as witnessed by the fo110wing:

* Linked with the ARGOS System The WMO-Hydronigèr Program onthe Niger Basin is operating 65 stations. The WHO is operatingnear1y a 100 stations in the who1e of West Africa for thepurpose of Onchocerciasis Control Program (OCP). The Office deMise en Valeur du Fleuve Senega1 (OMVS), has insta11ed 6stations 'network and will have 10 stations in operation' in1989, in the S~nega1 River and its main tributaries. Nationalhydro10gic organizations are a1so using satellite te1emetryfaci1ities, such as Benin (10 stations) and Guinea (5stations). On the other hand, 23 stations has been insta11ed inBrazi1 (Amazon) by ORSTOM-DNAEE, independent1y of HYWA.

* Linked with the METEOSAT System The Société Nationaled'E1ectricité . du Cameroun (SONEL) is operating a 10 stationsnetwork on the Sanaga River. A Meteosat network (12 stations)will be insta11ed in 1989 in the Zaire/Congo-Oubangui Basin,co-ordinated by ORSTOM.

The HYWA structure shou1d be first a co-ordinationorganization to ensure proper collection, processing anddissemination of the data by e1ectronic mai1box. This must beexecuted under international control toensure effective data­share between severa1 national organizations.

Softwares to process the data, in rea1 time are part of thesystem. There is a need to deve10p more mode11ing to improvethe benefit of these faci1ities.

24

3.12 Development and d;ssem;nation of PC softwares for ,,'databanks. process ~ interpretations, different from mathematicalmodels, to elaborate regional synthesis.

~ ~

There are serious gaps, like for instance in thees~ablishment inventory-diagnosis. A lot of data is (more or lessavailable and disseminated in many services, but it is notexploitable under its current heterogen form. So, most of thedata does not go beyond the state of arrid tables accompanied bya few comments, in internal reports, that is to say with littleor no use for anyone but a specialist. Cullens (1987) reportsthat considerable funds are spent in monitoring water quality,yet there appears to be a poor return for this investment.Stewart (1989) mentions justly that too little emphasis is placedin the ultimate use of data.

One of the first reasons, for this situation is the lack ofthe lack of data proccessing protocols and facilities, in frontof the high number of data that constitute a specific difficultyin the water quality studies. The proliferation of data starts inthe field and in the laboratory. Yet at this level, PC~tools musthelpcalculate and store the data, if possible directly from theanalysis instrument to the computer.Then, other softwares mustconstitute a data bank, in which historical information instations is very important. Specific process and interpretationsoftwares, directly connected to th~ data bank, must be developedor adapted, including statistics, relationships-extrapolation,drawing and mapping on ploter, expert systems, in order toproduce a directly synthetic document that could be· published. Ofcourse, the linking of the hydrometry-quality data isindispensable.

3.13 Biological monitoring. There is a great interest incoupling both the chemical-physical monitoring with biologicalmonitori~g, of which design thecnics are to be developed. Impacton life is'the main purpose of water quality studies. Biologicalchanges induced by pollution seldom or never are directlyindicated by chemical and physical measurements, such as oncedefined, sensitive biological communities may be the indicatorso~ trends, more integrated to events than classical pollutionmeasurements by themselves. Relationship and multivariatepackages for chemical and biological data sets, by mean ofmicrocomputers may be sorne of the techniques to be applied. Thiswould mean sorne form of multidisciplinary staff, that barely wasapplied but that definitely needs to be developed.

In the last decades, taxonomy has lost importance ;n thebiological sciences. However,' pollution impact on aquatic biotais based on the identification of plants and animals, and theirappropriate groups. It can only be shown with a precise knowledgeof taxonomy, a speciality that must once again be valued.

/

25

10. AQUATIC TROPICAL DISEASE VECTORS, PARASITES AND·PESTICIDES

CONTRàL-IN HEALTH AND AGRICULTURE SECTORS

1.General aspects

1.1. Two types of pollution, interrelated,affect tropical inlandwaters, which create serious hazards for human health and theaQuatic environment.

The big human or animal endemics and the epizooties rageheavily in the humid tropics: onchocerciasis, malaria, yellowfever, dengue, dracunculiasis, trypanosomiasis, leishmaniasis,bilharziazis, etc... The vectors or their larvae live in water,as well as the parasite itself sometimes (bilharziazis). This is aform of biological water pollution, whose extensive control byinsecticides, molluscicides and herbicides leads to another typeof contamination of the hydrosphere.

1.2. In other respects, in agriculture, disease and predationcontrol treatments against various parasites or animal (micro­parasites, insects, birds, rodents, etc ... ) and land or waterweeding are accomplished by insecticide, fungicide or herbicidespraying, in order to improve the yield of rice, cotton, sugarcane, citrus, palm, soya, etc ... The same substances are oftenused in vector and agriculture control.

1.3. Thus, pesticides ~ one of the most preoccupying pollutionin the humid tropics, now and in the future, because of the manyattacks in wide areas of the hydrosystems.

1.4. Many articles and books on the toxicity of pesticides havebeen published in the world since the 1960's, but they have beenscarce for the humid tropics. Among this abundant litterature,let us indicate that the WHO (1986) has published on sprayingconditions, degradability in the environment, exposure type forman (air, water, food, contact), metabolism and effects onhealth. C. Dejoux (1985, 1988) made an exhaustive study aboutthe impact of vectors and agriculture control programmes onthe aquatic environment in Africa.

2. Chemistry. remanence ~ relative toxic;ty of pesticides

2.1. The products used are classified in different groups'Organochlorides: the first synthetized, the most ubiquitous.Not very soluble in water, soluble in oil, accumulation ingreases. Generally long remanence: benefit and danger. Mainchemical species DDT, Aldrine and Dieldrine, Chlordane,Hexachlorobenzene, heptachlore and heptachlore epoxyde, lindane,metoxychlore, 2, 4 - D. The HCH isomers (i.e. lindane) are amongthe most soluble in water.Organophosphorus : less remanent. Ex. : Parathion, Malathion,TEPP, phosdrine.Pyreth~oids : Natural and synthetic. Average remanence in water.

26

Sticks quickly on organic matter. Generally, toxicity is veryhigh. They would account for a high percentage in the worldmarket. Pyrethre is a tropical chrysanteum and the use ofpyrethroids is sometimes mentioned as biological control.Organic or organe metallic compounds: are used as herbicides.Derived from urea, thioural, tiazenes, etc... Carbamates anddithio-carbamates are fungicides. Some are natural.Mineral substances; Ancient, but still in use. Compounds ofmercury, copper (sulphates), tin, sulphur, etc... Mercurysalts are used the most, despite a high residual toxicity.Bacterial products : They are "biological insecticides", such asBacillus thuringiensis israelensis. It is a bacterium whosespores produce a toxic cristallized protein. H14 serotypedestroys the larvae of some insects (mosquitoes, simulies). It isnot very toxic ( Dejoux C. ,1979).

2.2. The works of Pimentel (1971), Alabaster (1969), anon.SPVAG(1981), Dejoux (1988), establish a relative scale of toxicity fordozens of pesticides. Thus, sorne products may be mildly toxic forthe environment (Temephos -Abate-, Bacillus t.i.), while other(Endrine, Dieldrine, Endosulfan, pyrethrinoides, etc ... ) canaffect strongly the aquatic medium. The toxicity of a pesticidedepends on its formulation; nevertheless, organo-chlorides aremore toxic than organo-phosphorus. Herbicides are generally lesstoxic, at least towards fish. However, the proliferation ofchemical formulations and the increase of the spreaded quantitiesare so fast (Smith and Lossey, 1981) that the consequences ofmany pesticides and their behaviour in the hydrosystems are notsufficiently known (biodegradability, residual products more orless toxic than the original substances, etc .. ).

2.3. It is known that sorne products, whose aoclication i§prohibited in industrialized countries, are still being usedin developing countries, because of their large scope of actionand their low prices (DDT, HCH, etc ... ). The chemical amounts andspecies of pesticides used are often not accounted for at anational level in the humid tropics ( thousands of tons for themost advanced countries).

3. BehaviQur And effects Qf pestjcides in humid tropical hydro­systems

3.1. In the last decades, important control programmes for theeradication of vectors (breaking of the cycle) have been workedout, more often with the sponsorship of' internationalorganizations, sometimes within a twenty years period. In thesame manner, treatments in agriculture are becoming moresystematic. Public opinion (sometimes in the form of groups ororganizations) have exerted pressure against the intensive use ofpesticides, letting some governements face a dilemma : Protectionof public health and production on one hand, environmentdegradation and backlash on public health on the other.

This is why big vectors eradication programmes or

27

agricultural treatments, are considered with all the attentionthey deserve in every one of their phases. Nevertheless, theparallel scientific operations that are associated with themstill are difficult.

3.2. The chemical substances used often have a very hightoxicity which contaminates directly or indirectly the aquaticmediums. They lead to a high mortality of non-targeted organisms.They accumulate in sediments, weeds and a'-l along the food chainat higher concentrations than in the water, sometimes in theorder of 1000 times or more. The accumulati6n begins inmicroorganisms (Johnson and Kennedy, 1973), then phytoplancton,zooplancton, invertebrates, to end up in fish and man (Dejoux,1975, 1985, 1988). These contaminations can irreversibly damagethe ecological balance, in which human health or sources ofproteins (fish stock). Besides accidents that happen in treatmentoperations, the effects of pesticides on inland hydrosystems . aremostly mild. An indirect effect can be a diminution of plancton,and of the oxygen concentration, and a modification of pH andC02. In humid tropical countries, these problems were examinedlong after the beginning of the treatments, and specific worksare rare. Dejoux (1988) details the investigations realized inWest Africa, especially as a part of the onchocerciasis controlprogrammes. The impact on the environment has been studied,during the selection of insecticides (with different emergedgutters), according to the insecticides and organisms tested), aswell as during routine t~eatments. The different links of thefood chain were taken into account. Studies on the impact ofother pesticides have also been carried out in other countries(Nile Victoria in Uganda, Sudan, etc ... ). There is availabilitythen for some control programmes, of the main characteristics ofthe undertaken treatments, as well as a synthesis related withtheir impact on the non-targeted fauna. Generally, it appearsthat most of the products tested have a strong toxicity.

3.3. During many years, man was not concerned aboutO thetoxicity of the products he was using. Nowadays, variousthousands of substances have been tested by the WHO and about onehundred of them have been the object of in situ studies.Nevertheless, while there is more concern about their ichtyotoxi­city, the products without leading to a visible fish mortalitycan have a serious impact on sorne other groups of the aquaticfauna. Indeed, one sel dom has access to a product that savesinvertebrates. Consequently, fishes who feed on them, die orleave the area.

Ernphasis has been put on the fact that the elimination ofpredators of the targeted group decreases considerably naturalcontrol. It increases the risk of proliferation of the targetedspecies after the end of the treatment. Man is now conscious thateradication of vector insect species is not feasible, but that itis feasible to eliminate the ·parasite. Concomitant destruction ofother organisms, that would eventually contribute to impede thepropagation of various diseases, is sometimes considered as anegative aspect of the treatment. Because of a reinfection of

28

vectors from non treated zones, even far away, and a tendency ofvectors to become more resistant to the applied pesticides, wecan predict an intensification of vectorial control, that couldlead to a continuous contamination of the hydrosystems by a setof pesticides with a range of various effects.

4. Factors of transfer of pesticides through the hvdrosystems

Many factors are influent:- The chemical characteristics of the pesticide are determinant :solubility, resistance to physical and biochemical degradation,qualities of the degradation sub-products, that can be more orless toxic and resistant than the precursor.- The conditions of injection: Concentration of use, non-

point or 'point injection, duration and frequencies.- The general flow is determined by air and water dynamics :meteorological conditions during the treatment (wind,evaporation, humidity, etc ... ), height and intensity of rainfall,run-off and solid transport flows ( Bader J.C. et al., 1987;Gioda A. et al.,1988; Le Barbe L. et al., 1987 ). In agriculture,the treatment steps at variable distances of water masses;toxicity may decrease when they are reached, meanwhile invector control, running or stagnating waters are directlytreated, therefore directly hit by the poison. Punctualaccidents, sometimes serious, must also be taken into account.- The characteristics of the medium and its interferencesalso have an influence: nature of the soil, mechanical action ofthe plants, chemistry of the waters, air temperature andhumidity, etc ... Interactions with the mineral and biologicalmedium govern largely the gradual transformation of theprecursors. For example, organochlorides are easily adsorbed onsuspended matters and sediments, and then can progressively bewashed-out or retaken by erosion. It is conceivable that anefficient use of mathematical models could be tricky, due to thelarge number of parameters that must be included in theiralgorithms, the selection of the values is therefore difficult.

5. ~ QI fighting the agents Qi' tropical diseases snQ pollytionQy pesticides ~ the integrated control

5.1. Only the search of g set of diverse complementary technics(integrated control) adapted to the humid tropics countries, willallow the control of vectors and parasites of human, animal orvegetal diseases. The treatment with pesticides must beconsidered only as one of them. Thus, if a set of technicsallows a reduction in the expansion of pesticides, this shouldhelp in decreasing the contamination of the hydrosystems.

This means that integrated control is the solution for thefuture, with its methods that associate :- Administrative and scientific structure- Socio-medical education- Minimum and rational treatment, with means scientifically con-

trolled and oriented- Contribution of one or more biological agents, predators or

29

competitives- Management· of the aquatic (mostly hydrological) and vegetal

mediums.- Contaminated water treatment

Population and animal therapy.

The schitosomiazis control in the tropicalillustrates, among other actions, the methodologyintegrated control. The World Bank sponsored more thanoperations for the control of this disease (Lake Volta,etc ... ) led by the WHO.

zonefor anthirty

. Ghana,

5.2. One of the most effective means;n this set is theavalaibility of a national and international legislation, and toapply it according to strict rules that can be so strong as toprohibit the use of sorne products. Every country must count withone functional administrative and scientific organization toauthorize products and supervise their use. In practice, thistask is difficult, mustly in agriculture. The search for aconsensus with the users seems necessary.

5.3. The intensification of individual and municipal education,particularly to eliminate direct feacal and urinary dumping inthe aquatic medium (case of bilharziazis) and the domestic larvalseats (mosquitoes and microorganisms), is a . very effectivemean.' Yet, these efforts $eem the least successful, because theeducational actions do not seem to be well transmitted tothe youngest part of the population (elementary and highschools) .

5.4. Choice Qi pesticides. technologies and conditions ofspreading are sorne fields where a lot still needs to be done.

We nead to have better knowledge of the toxicity of manyproducts, beyond absorption in rat or fish. The. use of "mild"pesticides, as Bacillus t.i., is a method that must improve, evenin the field of "natural" or synthetic chemistry. In the sameway, investigations must continue to determine the minimalnecessary amounts and the specifity of pesticides, in order tobe more effective on the targets and save the most of the non­targeted environment. The degrees of remanence of the products,and the impact, of their degradation products on the fauna andflora in tropical media must be better assessed. Treatment opera­tions must be undertaken along with exhaustive studies of impact,during in situ tests for the products selection as well as duringroutine spreadings. Permanent evaluation of the results isnecessary to be able to redirect the methodology of a treatmenttimely (amount, chemical nature, impact, etc ... ).

New treatment technics aimed to limit the propagation ofpesticides in the environment, such as screen traps, must beinvestigated.

The know-how of spreading tends to limit technicallyuseless propagation of pesticides.

and water transit speeds, dryingcontact zones·between savannah and

5.5. Biological control is one of the possibilities that mostneeds to be developed Predators ( fishes, gasteropods,insects, etc .. ) and competitives (close species of insects,molluscs, radiosterilized males, etc ... ). Weakening thetargeted species before and after treatment, allows a decreasein the amounts of the pesticides used . These methods have yetto be adapted and still very cautiously to the conditions of eachhumid tropical country. The general problem of the introductionof allochtonous species is particularly very tricky ( example ofrice-eating gasteropods ).

5.6. ~ knowledge of climatological and hydrological reQimessuch as wind,temperature, hygrometry, rainfall, height of rivers,di scharges , flooded areas and depths, etc ... , is indispensablefor integrated control. An inventory of the whole of the aquaticmedia is necessary to avoid reinfection of treated zones bynon-treated ones. All these results must be acquired before andduring the treatment programs. Prevision of the discharge bytelemetry and modelling in real time, and of the dosis /diffusion ratio according to local morphology and hydrodynamicexperiment, are direct contribution of hydrological technics inthe determination of the quality of substances to spray forvector control. A lot of works has done in premodel1ingthe effects of operations (Bader J.C. et al., 1987; Gioda A. etal. 1988; Le Barbe L. et al., 1987; Pouyaud B. et al. , 1987).Still, the dynamics of the substances, which are related to

.atmosphere and water dynamics, the chemical evolution that1s controlled by factors of the medium, such as trappings andselective bioaccumulations, interactions, autopurification,

-etc ••. , make the application of theoretica1 exhaustive models-difficult. Besides, their transfer to other sites than the onewhere they have been adapted is delicate.

5.7. ~ cleaning action of the aquatic medium by undertakingrealization of public works is a basic method to take intoaccount in . plans of preventive or hydrologicalrehabilitation (curative). These mechanical instruments representa fundamental contribution to sanitary battles.

- Deviation, sweeping, alternated drying of natural reactives oropened sewers, depending on the life span of targeted and non­targeted organisms.- Improvement of drainageof damps, humid swamps,forest.- Removal of domestic seats.- Building of vertical wall spillways. Removal of rockythresholds, collapsed works, natural pits upstream and downstreamthe beds. Solidifying the basins of bridges, channels. Use ofpipes for wells and road equipment.

- Improvement of withdrawal technics in order to avoidpollution of the rope and the bucket. Solidifying and drainingthe peripheries of the well; perimeter of protection. Setting ofdrill holes equiped with hand pumps. .

31

- Withdrawa1 of over abundant plants. Etc ...

5.8. The treatment of drinking waters can e1iminate or diminishthe contents of pe9ticides.,

F10ccu1ation,effective. One needsradiation.

decantation and ultra-violetsto know more about the use

can beof solar

Activated carbon (powder or beads) can contribute topo11utant trapping; but high doses are sometimes necessary.Neverthe1ess, even apparent1y used up carbon can still contributeto the e1imination of pesticides.

A bio10gic treatment, rea1ized under certain conditions,a1so e1iminates a large part of the substances.

5.9. Therapies that consist in treating the who1e affectedpopulation with specific drugs come a10ng with the other methods.To conc1ude, integrated control of water qua1ity, re1ated to thefight against p1agues (vectors, parasites, pesticides) appears asa wide field of mu1tidiscip1inary interventions, in which

e hydro10gy must take an important place in different aspects. Thehumid tropics countries must be more organized in that sensein order to have the avai1abi1ity of these specia1izedtechnics, a crucial question for their agriculture andpopu1ation's hea1th.

11. MICROBIOLOGICAL ASPECTS OF WATER QUALITY CONTROL IN THE HUMID

TROPICS, CONCERNING DRINKING AND RECREATIONAL WATER

1. General aspects

Despite the momentum created by the International DrinkingWater Supp1y and Sanitation Decade, progress can hard1y match theincrease in population size (Prost, 1989). Drinking water supp1yof acceptable qua1ity and quantity for every man is far frombeing reached but must remain a high priority for the year 2000,as one of the most important factors of mankind's hea1th.

In many countries of the humid tropics water kil1s, whereasit shou1d be a source of life and hea1th. The first objective ofany program to manage water quality should therefore be toidentify how many and overmore why people die due to waterre1ated problems (cf. paragraph 1) and seek the most effectiveapproaches and researches (cf. paragraphs 2-5) to reduce thenumber of deaths (R.E. Man1ey).

Microbio10gica1 aspects that dea1 with_water qua1ity control

theand

by

32

are numerous. Bacteria, viruses, fungi, insects, larvae, worms,etc ... are the causes of water-associated diseases whichare very common in the humid tropics, more than chemical andmicro-toxic pollution.

Vectorial diseases, whose parasitical cycles include anaquatic phase, are, together with feacal pollution, the maincauses of man's poor health in the Humid Tropics. Hundreds ofmillions of people are contaminated. The aspects of vectorialdiseases control, and its consequences on water pollution, arethe object of a special chapter.

On the other hand, however, bacteriological methods providethe mean to detect these kinds of pollution, (analytic aspect),while bacteriological processes realize purification of water andwaste water in the environment, and in treatment stations orlagoons, or of residues in digestors (treatment plants). In thischapter, hospital pollution could be added to feacal pollution.

2. Eescal bacterial contamination patterns in the humid tropics

The knowledge of the feacal bacterial contaminationpatterns is necessary for decision-making dealing with water ~quality control.

2.1. Eeacal water-borne diseases : Cholera, dysentery, gastroen­teritis, other diarrheas, typhoïd, infectious hepatitis, somevectorial diseases (bilharziasis).

2.2. ln ryral ~, feacal pollution, though often localized,presents some serious aspects

- Bad drainage and no protection around the wells and invillages. Contaminated water stagnates with man (children)animal's excrements. The string and bucket are contaminatedthis polluted wate~at each withdrawal.

- Water and excrements remain in small ponds and puddles. There,organic matter favours the developent of germs (notablyEscherichia coli).

- lack of individual and community latrines. Excrements aredropped everywhere, particularly on river banks by men andanimals, or directly into the water (life on boats), at thesame place where water is used for drinking and personalwashing. The remaining pollution is sweeped during the floods.During the dry season, low dilution increases the contents.

- Watering of vegetables with feacally (or chemically) contaminedwater brings diseases to the town where these products aresolde

- Agricultural re-use of municipal effluents may be a sourc~ ofcontamination. After Prost (1989), a WHO scientific grouprecommended to relax the bacterial guidelines for waste wateruse in agriculture ( WHO,1989 ). It recommended, on the basisof epidemiological evidence' and of available water treatmenttechnologies, thatwater used for the irrigation of ediblecrops contains less than 10,000 feacal coliforms per liter,

and that irrigation of fodder crops, industrial crops, andtrees be permitted after the retention of waste water for 10

_ days in stabilization ponds.

2.3. ln urban area:- Waste water open channels are used in the same way as the river

banks in the country side, and moreover, are used as wastedisposal which remain there between the big floods.Unsatisfactory waste water 'treatments lead the non-treatedurban effluents to natural lagoons or streams where feacalcontamination is high. It is one of the most important sourcesof pollution.Septic tanks are rare. Like draining well latrines~ they aresometimes cleaned out by throwing residues without treatment toan aquatic medium. 'Locally, they can contaminate neighboringwater wells. Even when toi lets exist, hygienic paper is notusually thrown into the bowl.Clean water, coming from a waste water treatment station,can remain contaminated by pathogenic germs~

Downstream sediments are contaminated locally and by urbaneffluents, and come back to the town with pathogenic germs, foruse in construction, where they constitute a 'hazard forthe building workers.

2. Appropriate microbiological indicators of feacal ~ otherpathogenic pollution. ~ for tests and alarm

The difficulty of finding significant feacal indicatorsis a major problem

If feacal microorganisms appear in drinking water, normallyalarm must be given, even though they can be not pathogenic. Theyare generally feacal coliforms and feacal streptococci; they maybe enteroviruses. Other bacteria such as coliforms or sulfite­reductor Clostridium are ubiquitous, and are surely not indica­tors of feacal pollution. Moreover, other microorganisms, forinstance fungi, actinomicetes, etc ... , may be responsible forhealth troubles in man. Oxydant or reductor bacteria can bedamaging for water supply and waste water networks.

alarm, or as tests to estimate the(for instance, the resistance of

is similar to that of Salmonella).to guarantee the public health ofthe tropics and their economic

Indicators are used forefficiency of a treatmentcoliforms to desinfectionThen they are basic toolsthe people living indevelopment.

However, the problem is not so simple, and is atopic. Research about suitable microbiologicalfeacal and other pathogenic pollution, usedalarm, is carried out in the most advancedcountries, but needs to be more expanded andreflexion on the base of the results obtained inwhole. / 1

much discussedindicators ofas probes andhumid tropicssubmitted to

the Zone as a

34

Research concerns :Specific humid tropical species, according to local conditions:total coliforms, fecal coliforms, identification and isolationof Salmonella, identification of entoviruses, fungi, actinome­cetes, etc ...

The complexity of that issue appears with the researchworks of Fujioka '(1981-1989) and Hazen (1981-1989).

Hazen (1989), mentioning Bonde's eight criteria of anideal feacal-pathogen indicator (1977), examines variousstudies about bacteria ( E. coli, feacal streptococci,Bifidobacterium spp., Clostridium perfringens), viruses,and bacteriophages as candidates to this purpose. Heconcludes that certainly the standard feacal indicator E. coliis unacceptable. Because few studies have reported the useof feacal indicators (other than E. coli) in tropicalsource water, objective evaluations of the efficacy of thesealternate indicators is difficult. At present, obligateanaerobes, or their phages seem the best candidates for abetter indicator for tropical source water, primarily due totheir inability to survive extraenterrally. However, all ofthese indicators have the inherent difficulty that they ortheir host may survive under sorne conditions and that themedia used for bacterial indicator enumeration may allowthe growth of false-positive background flora. The viablebut non-culturable phenomena reported for many pathogens inboth temperate and tropical waters suggests that indicatorsmay only rarely be corrrelated with disease risks in sourcewaters (Colwell et al.,1985; Hazen et al. ,1987; Baker et al.,1983). Thus the best indicator may be no indicator, i.e.direct enumeration of selected resistant pathogens. Thiswould allow a more realistic estimation of health risk.

After Hazen (1989), immunofluorescent staining candetect densities of pathogenic bacteria as low as 10 cell perml, a density which may give no cultural counts (Flierman etal., 1981; Colwell et al., 1985). The use of monoclonalantibodies makes this technique specific even at the straighlevels of sorne organisms. However, as a result of cross­reactivity when using immunofluorescence (even with mono­clonal antibodies) the most specific and sensitive methodsfor detecting pathoghens may be the nucleic acid probes (DNAor RNA). DNA probes have already been developed and testedfor enterotoxigenic E. coli (Bialkowska-Habrzanska, 1987; Hillet al.,1983; Moseley et al,1982) and Salmonella spp. (Fittset a 1. ,1983) . Thus direct detect i on of pathogens i scurrent. Common enteric pathogens which could beenumerated are poliovirus and Salmonella typhimurium.Detection of either one of these in tropical source waterwould indicate risk of human disease. Instead ofenumeration, maximum contaminant levels could be baseon detection only. One potential problem with this approachis that the presence or absence of one pathogen may havelittle bearing on other pathogens.!A multi-species test fortwo or more of the more resistant and common pathoghens found

35

in tropical waters may be necessary.

After Fujioka (1981-1987), many of the nationalregulations such as the use of bacterial indicators toassess water quality are not applicable to Hawaii because thebacterial indicators selected are .naturally present in theenvironment of these islands. On the contrary, aquaticorganisms selected fo~ toxicity assessment by USEPA are notpresent in Hawaii. On the other hand, sunlight, a naturalenvironmental agent which is more predominant in the tropicsthat in the temperate zones of the world, is the primaryfactor in the inactivating indicator bacteria in theenvironmental waters of Hawaii.

- Relative statistical distribution of germs, feacal indicators/non significative germs ratio, ~ feacal indicators/pathogenicgerms ratio, etc ... , which vary with local and periodicalconditions.

- Tests for detection of mutagenic substances, used withSalmonella typhimurium, enzymatic activator, extraction XADresine, liquid extraction, extraction of solid and lixivingresidues, etc ... (Salmonella/Mammalian Microsome MutagenicityAssay-AMES Assay).

- Selective analyses methods filtering membranes, multipletubes, gelose (incorporation, spreading); cultural medium andreactives; isolation and identification of Salmonella (Mooretechnic); determination of entoviruses in water; analyticalquality tests; signification and interpretation of bacterialanalyses, etc ...

4. Appropriate microb;ologicaJ water gyal;ty standards ~ le9;s­lat;on fQr drinking water ~ recreat;onal water in~ hymidtropics

WHO (1972; EFP/82.39; EFP/83.58 ; guide for drinking waterquality, 1986) proposes standards that are often used as grounds,for nat i ona l references, eventua11 y adapted by each ,countryunder specific conditions. The United States Public HealthService, 1977, France, The European Communities Council, 1975,1976, have adopted their own standards ( tables are available ).Many humid tropical countries have done the same or need to doso.

Most countries have no law that deal with the bacteriologicalquality of input water to treatment stations for drinkingwater. In this case, standards are only guidelines.Othermicroorganisms can be responsible for complaints (for instance,cutaneous diseases in recreational water), without inevitablybeing of feacal origin. Therefore the use of feacal indicatorsdoes not constitute an universal test for- Any hazard alarm.Only "classical" detections are made, but other water-associateddiseases whose microorganisms are not sistematically detected (may be unknown), should also prohibit the input of water witha strong feacal pollution to supply treatment stations.

36

The law usually determines standards with maximum thresholdvalues of 'total coliforms and feacal coliforms per volume inswimming water (for instance, 5000 total coliforms per 100 ml,2000 fecal coliforms per 100 ml, neither Salmonella nor virus ).In temperate countries, water is generally acceptablefor drinking only if it does not contains neither feacal norpathogenic germs and only a very small number of cultivablegerms (37 degrees, nutritive medium ). For instance, theadoption of general law text by the EEC·countries has recentlystrenghtened the standards for drinking water. Those areconsiderations given for example, but the studies of Fujiokaand Hazen have emphatisized that such standards have nosignificance in the tropical waters. In a general manner,Fujioka (1989) mentions that conditions in tropicalcountries will never be fully understood and tropical countrieswill continue to be forced to operate under assumptions whichoften are not applicable to their own conditions. Anyhow, theseobvious standards are not often respected in rural areas, wheretreatment stations do not exist. There, drinking water is takenfrom the common well or, more often, from the stream or thelake, at the same place that is reserved for personalwashing, swimming or animal watering. It becomes increasinglydifficult to attain WHO standard9 specially in respect to feacalcoliforms. Even in big cities, the performance of the existingstations is sometimes unsatisfactory, because of technical orhuman faults.

After Kilani (1989), there is a need for relaxation of theexisting Water Quality Standards in Kenya. Experience hasshown that the use of FC(indicator organisms) as an indicationof feacal contamination and therefore presence of pathogens isa luxury that may no longer be afforded in rural water supply.It is to be hoped that research work starts in this area.

A serious problem is the unavaibility of published data tocharacterize the quality of waters in the tropical zone. As wellas for standards in general, it would be very useful to make anexhaustive review and comparison~of bacterial standards or guide­lines determined in each humid tropical country for both supplyand waste water of treatment stations.

As background of standards and law, research shouldidentify more the' bacterial flora of water sources anddistribution systems in these countries.

It is a need to develop better technics to detect andenumerate various pathogens and indicators in water withoutthe bias of guidelines established for temperate countries.Only withsuch backgrounds, microbiological monitoring of waterquality will have significance.

Epidemiological works are needed on health hazards fromvarious standards of water, including the rel~tionship betweencyanobacteria (and phytoplancton) in wate~storages and theeffects on human health. Epidemiological statistics, "in real

37, 1

time~; could be also considered as efficient indicators forawareness.

In relation to,this, the identification of environmentalconditions that lead to unusual occurrences of health significantor nuisance organisms must be carried out, according to thescheme exposed for feacal contamination, (paragraph 2).

5. ~ Qi microorganisms in the biodegradability of organic,matter. chem;cal sybstances and industrial waste

This aspect of microbiology grows higher in the humidtropics because temperatures are a favourable factor forbiodegradability, in spite of the decrease in the dissolvedoxygen content. Biodegradability in an anaerooic medium is also aresearch theme of great interest, able to provide poweralternatives.

Particularities' in the acting of unique or common aerobicspecies in diverse humid and hot local conditions, such. asactivated sludges, ponds, /aerated media, disgestors, accordingto the types of waste, can be useful knowledge for these puri­fication technics. Numerous studies to be carried out shouldcorrespond to the diverse operational technics which exploit verydifferent mediums.

The main items to consider in the microbiological andbiochemical area are microbiology of degradation in humidtropics water and soil; aerobic and anaerobic processes,metanogenic and non metanogenic bacteria, methods of analysis andtests, pecul~ar kinetic processes, reaction velocity,characteristics, kinetic and control of parameters, mixtureregime, operational problems such as starting up and routine,cases of herbicides, detergents, hydrocarbons, etc ...

6. ~ Qi bacterial water pollution control in the humid trop;cs

Ways of bacterial water pollution control in the humidtropics are quite diverse and complementary. Some arecheap, sorne are expensive 1 but they must be appliedtogether at each corresponding level. The cheapest ways arecapable to efficiently alleviate the most urgent problemsin most of the areas, but would nevertheless need educationand grants from the governements and internationalorganizations. For example, mentioning Prost (1989),cyclops, vector of the Guinea Worm, are relativelylarge animals which can be removed through filters madeof cotton, nylon, or polyester clotho

, The following issues can be interpretated as scientific.technical or an economic research study, or training to bedeveloped in most countries.

6.1. General means against bacterial pollution

38

- Individual education, in order to obtain personal participationafter hazard comprehension.

- Organization of control at individual, municipal, departmentallevels (urban, rural zones), with alarm systems for particularcases.

- Identification and characterization of those microbiologicaldrinking and natural water problems that may, directly orindirectly, adversely affect the local public health.Identification of those microbiological organisms for whichlocal adequate control methods are not available, and thenresearch and development of the needed control methodologies.

- Identification of parameters of water quality improvement.- Identification, characterization and development of methods

for removal and/or destruction of biological (and chemical)pollutants of hazardous nature.

- Research and technology on treatment systems for specific controlof water pollution by carcinogenic, teratogenic and mutagenicsubstances.

"- System engineering approach to the" solutions of water qualityproblems.

- Development of data base for drinking water quality control,and assessment for domestic and recreationalpurposes. "Quantify uncertainty in risk assessment for water qualitycontrol.

- Develop mathematical models for water quality control.

6.2. Means aga;nst bacter;al contamination Qf waste water

-Construction of sewage disposal systems through the stages ofthe collection and conveyance networks as well as treatment anddisposal of domestic waste water. However, until a satisfactoryremoval of feacal pollution is reached, treatment of collectedeffluents remains difficult, and the outpout water contributesto the pollution of hydrosystems. In this case, a dischargeinto the sea is preferable, because most of the bacteriacan not survive in salted water.

- Downstream desinfection of effluents of waste water treatmentstations with oxidants.

- Controled "lagoonage" is a solution to be considered as oftenas possible. strong solar radiation favours the destruction ofgerms. Research on biodegradability must be developed in thehumid tropics : microbiology and applied technology.

- Reduction of feacal pollution by the construction of small andcheap individual or municipal systems (unsewered sanitation),based consumption (see: Colcanap et Dufour, 1982). In ruralarea, communal facilities can be planned ( such as compostsystems), but often present social difficulties.

6.3. Means against bacterial contamination of drinking water andrecreational water

Protection of water resources used for drinking water andrecrational water, overall upper watersheds and ground water :geological, hydrological, hydrogeological, social studies.

and

recreation,Policy forby unaware

39

Generally there can exist pressure to open up water supplycatchments for recreation or other uses: there are threats topoison water supply.

- Analysis to quantify the main contamination problemslocating the places where they are most severe.

- Protection of water in contact during work oror used for cloth or personal washing.impeding the use or contact of contamined waterpeople.

- Water treatment of individual and community swimming poolstest controls, operational technics for treatment (floculation,filtration, disinfection); quality control; legislation.Bacteriological standards do not guarantee against virusessuch as thyphoid and infectious hepatitis. Sand filters andchlorination would not eliminate hepatitis viruses (Smith,1969). Classic analyses cannot detect some toxics or viruses,in the same way as classic treatments cannot remove them. Theproliferation of toxic substances in agriculture and vectorialcontrol represents an actual risk in the humid tropics. There­fore, appropriate standards for the use of toxics and wastewater disposal, constitute also priority measures in theprotection of drinking water, since the generalization ofdomestic water supply will not be achieved by year 2000. Thelack of such standards, and the difficulty in detecting alltypes of hazards, must lead to avoid the use of too muchpolluted water in supplying treatment stations.

- Increase of the number and quality of municipal and domestictreatment stations and other supply systems:a) Sedimentation, flocculation, filtration.b) Chlorination, cleaning and desinfection of water tanks

* oxidants (chlorination, ozonization, etc ... ), oligodynami­zation, other new desinfection, Physico-chemisal characte­ristics and qualityof reactives. Reactions with microor­ganisms (and organic and inorganic components)

* technics : local production of oxidant, place and time ofinjection, equipment, continuous and emergency desin­fection, super chlorination, contact time

* control technics security, residual contents,dechlorination, quality of reactives, applied microbiologyto operational control .

* standards and legislation.c) Piped and tap water supply in the household itself,

better than public standpost.d) Simple and inexpensive domestic water supply systems,

granted by the governments and international organizations :* pipes and tanks for rain water collection and storage

from roof run-off: potential and availabilityof rainwater supply, reliability during each month, roof area;household demand; optimum tank size; types of concrete(with bamboo), metal, plastic tanks; use of mathematicalmodels for such studies. The withdrawal system from thesetanks and the desinfection processes are also importantissues. Prost (1989) justly points out that small amountsof water are drawn all day long from the main jar, using

40

smalJl:·:·.:~cùps depôs i ted nearby. l t i 8 obv i ous that eachcollection contaminates the reserve. The multiplication'of~bactèria after a certain period of time is sufficient 'to. create significant risk. 50, periodic desinfection ofwater tanks (ground cistern, roof cistern) is likelythe

...i:main aspect of these systems .• ,- Technics of construction and (once again) maintenance of: small flocculation tanks and sand / carbon filtèrs for:> .vi 11 ages. .* Use and local production of kitchen gravity filters made

of porous ceramic. This is a main issue because, in manyareas, piped and tap water is not supplied or, if it is,its quality is generally dubious. The quality needs anultimate treatment just before consumption. Only somelitres of water are drunk per family per day, which can besafely provided by such simple filters. For instance, inBolivia, price of a porous cell, imported from Brazil is3 US$. The complete system (2 superposed tahks of 4litres), is more expensive but could be' cheaplymanufactured . locally, with large publicity anddi stri bution. . .

* Hydrological studies and technics for the b~il~ing,setting upand maintenance of hand-pumps/small bore-holeswith "crepine" to avoid pollution of· the wells from thesurface or the use of surface water. This technics shouldbe developed everywhere sandy phreatic aquifers exits.

12.'DOMESTIC AND INDUSTRIAL POLLUTION CONTROL: ORGANIC MATTER,

NITROGEN AND PHOSPHATUS; EUTROPHICATION. SANITATION, SEWAGE

AND WATER DISPOSAL

1. Types 2f' yrban AnQ indystrjal pollytjon

In the humid tropics, the exploding growth of the· citiesand th~ accompanying development of industries, which isoriented to the exploitation and transformation of biologicalresources (vegetal and animal), often in the same place,determine a dominating pollution by organic load and suspendedmatter. A high rate of fecal contamination, which is sometimesaccompanied also by inorganic toxics, exists. Pollution byhydrocarbons constitutes a special form of organic contamination.

According to the countries, the cause of major pollution inurban area is domestic waste water and solid water, or on thecontrary, industrial waste water.

2. Cayses And aspects Qf organic pollytion,

2.1. Waste evacuation. and.disposal if they exist, areportionate domestic production.

in particular, waste waterrapidly unsuited for a dispro-

The biodegradable organic pollution proceeding from theindustry originates in slaughterhouses, dairy industries scanneries, pulp and cellulose mills, wood transformation,breweries, fruit juice factories (citrics, pineapple, ... ), oilmills and soap factories, sugar cane, coffee, rubber, cocoa, ricetransformation, extraction zones of hydrocarbons, refineries,garages, etc ...

2.2. Tropical storms generate urban floods which sweep allof waste and waste water. Rain water and waste water networks are·generally not separated, which increases the difficulty oftreatment and the pollution of the receiving media. Floodor pollution basins do not exist on drainage networks.

2.3.Eutrophication and landscape deterioation appear over more orless large areas, with the pollution by domestic or industrialorganic waste water, becauseof oxygen depletion and the highproduction of nitrogen and phosphorus. Phosphorus (phosphate andphosphoric acid) and nitrogen, which are very much used in theagro-alimentary industry for instance, contribute as pointsources to eutrophication. This phenomenum can be stronger wheretoxic contamination is low. Self-purification of the water isnot sufficient, particularly where the turn-over is slow.Eutrophica4ion injures biocenoses: growth of primary production­and weeds is observed and contributes by decomposing theincrease of nutrients and BOO, rarefaction of animal species andproliferation of sorne species of fishes, development of vectors,etc ... Sitting and smelling gases correspond to the anaerobicdeposition of organic and suspended matter and sand.

2.4. Pollution Qy hydrocarbons in the humid tropics (Andren,1976; Orokoya, .1978; Oejoux, 1988) is limited to"the extractionzones and refineries. Accidents in transportion eventuallycreate" local problems. The many individual disposals of wasteoil, wherever, and sometimes directly in the aquatic medium, areoften the source of the'most important form of water pollution byhydrocarbons. Lagoons with a low turn-over are affected the mostby this type of pollution.

Hydrocarbons form an asphyxiating film over the water andlimit oxygen exchanges through the surface. Sorne of themevaporate. Compact residues remain, the soluble phases enrich ;naromatic compounds, both with toxic potentials. Oegradability bybacteria, more active under a high temperature, can producesubstances that are more toxic than crude oil, especially whenthey are dissolved in the upper part of the water, Refinedproducts are generally more toxic than crude oil, and, moreover,can have an anti-bacterial action (kerosene), that inhibitsbiodegradation.

Little is known about the consequences of hydrocarbon

· 42

pollution in continental waters, besides the effects ofcatastrophic accidents: black tide in the sea. However, it iscertain-that the use of detergents to make hydrocarbons disappearis worst for aquatic 1ife than the hydrocarbons themse1ves.

2.5.Po11utjon Qy detergents is increasing in the humid tropics.

Then, the status of urban and industria1 environmenthea1thiness is genera11y very deficient. This is particular1y truefor aquatic media, such as 1agoons, groundwater, drinking watersources, estuaries with 1ittle stream input, which may receiveuntreated waste water. Domestic pollution in smal1 towns, withoutindustry, is also preoccupying.

3. Waste A02 waste water djsposa1

The problem of waste and waste water collection,disposal and treatment by appropriate processes for cities, townsor villages, seems one of the most important for man's health anddignity in the humid tropics (see chap. about feacal pollution).

The studies made on the city of Abidjan by Broche andPejchet (1983), Chantraine and Dufour (1983), and summarized byOejoux (1988), are examples of research about the evacuation andtreatment of the waters of a great urban centre in a tropicallagoon zone. They lead to the modelling (in terms of BOO) of thepollution deriving from various urban and industrial sectors, andtransported through different systems ( sewers, surface drainage,run-off ) to the outlet lagoon.

:- Softwares dealing with waste water networks have beenelaborated by several specialized services. They allow, partlyor tàta1ly, various estimates of run-off on urban watersheds andthrough waste water networks, with the determination of thepiezometric 1ine, according to actua1 or fictitious rainfalls.Other estimates about spil1ways, siphons, succints arefaci1itated. Visualization of hyetograms and hydrograms,and longitudinal profiles are availab1e. The direct discharge inthe natura1 medium is evaluated through the hydrau1icmonitoring of the existing networks, and the simulation of the 1

functioning spillways and storm basins.

Urban drainage is often difficult because of the extensionof the town a11 along the coast or the bank, almost at the leve1of the sea or the lagoon.

4. ~ Qi organjc. njtrogen ~ Dhosphatys po1lytion control

The means of organic pollution control in-villages andcities include those already mentioned about bacterial contamina­tion control. Many studies must be undertaken to adapt and com­plete the knowledge on specific conditions of the humid tropics :

4.1. Individual or community waste collection and waste watertreatment systems. These remain the best methods to avoid organic

43

and

natural

Technics

and dust;into air

elimination

artificial or

treatment,

septic tank.

(by anaerobic bacteria).nitrogen contaminationwith retention of soot

of water pollution

pollution of the hydrosphere, Wi\~h high contents of nitrogen andphosporus. However, design and m nagment of such systems reQuirean adequate understanding of many phenomena.

- The biochemical phenomena which determine the functioningof the treatment systems, according to the type of organic

pollution. The processes which remove nitrogen and phosphorus inthese systemé, need complementary ~esearch for determining designparameters used in particular for modelling.

- The study of the flock, activated sludge, deposition anddecomposition of the ~udge in humid tropics.

- The conditions of the biodegradability of specificsubstances.

- The metabolisation of hydrocarbons and phenolic products.- The adapted technology for water treatment, bacteria,

physico-chemistry and biochemistry of :Activated sludge spread over different types of soil,with infiltration and draihageAreal lagoon and no-areal lagoon,wetlandsbacterial bedIndividual sanitation

- The Tertiary treatments. bactericides

nitrogen eliminationfor the reduction ofwaste incinerationwithout transferencepollution.

- Creation of technical attendance for the functioning ofpurification stations, training of specialized engineers in thepublic services for community stations and individual systems.

- The study of the mixing of polluted water (urban +industry) for optimal degradability. Selection of microflora.Effects of the addition of nitrogen and phosphorus ( eliminationof phenols ).

- The problems of thevalorization of waste and sludge

* anaerobic digestor: power source, functioning problems,harmful effects

* desiccation, transport* valorization knowledge of the product. Minimum

treatment. Periodic analyses control (toxics, heavymetals, microbiology). Desiccation.Use in agriculture. Pasty or liquid spreading.Comparative tests for crops, forest, soil condition -andclimate. Promotion with farmers. Risk of the reuse ofuntreated waste water, waste or sludge in agriculture, inthe expansion of enteric diseases.-

* Improvement of sewer networks ( open or piped). Separa­tion of pluvial and waste water networks.

4.2. Study of the causesindustrial pollution·

and effects ofeutrophication.

44

4.3. Cbemical and biological pathways

In order to predict eutrophication and to assess managementstrategies, biochemical and physical chemical processes occuringin natural or artificial media must be better known in their mainpathways.

- Study of microbiological populations, including patho­genic, protozoa, rotiferes, nematode threadworms, algae, fungi,that intervene in the self-purification of the environment,lagoonage, activated sludges, bacterial beds, septic tanks,anaerobic digestors. Role of microorganisms in the biochemicalprocesses concerning nutrients in hydrosystems.

- Study of local pollution effects, as suspended matters,color, transparency, temperature, radioactivity, pH, Eh-rh,salinity, chlorides, nitrogene, phosphorus, sulphur, carbon,iron, manganese, etc ...

- Oissolved oxygen balance in aquatic media* Estimation of the balance terms.* Role of photosynthesis in self-purification

. radiation, temperature, Influence Oof thermicpollution and natural high temperature.biological sample and measuring such as algalbiomass, including in situ chlorophyll measurementand investigation of photosynthetic pigments(potential indicators of nuisance ).

* Diurnal variation* Longitudinal profile of dissolved oxygen concentration

downstream a pollution. Sag curve.* Hypolimnion aeration and destratification.

- Local processes of the nitrogen and phosphorus cycles, inpolluted aquatic media and treatment systems (wetlands, ponds,flooded plains: varzoes, pantanales, yaeres) :

* Nitrification and denitrification. Tertiary treatmentto reduce nitrogen.

* Interaction (removal/release) between phosphorus andsuspension or bottom sediment.

* Nitrogen and phosphorus control plant production.* N/P ratio and limiting role of each nutrient.* Transport of particulate phosphorus maintaining an

an eutrophic system over following years.* Sediment oxydation with nitrates, sediment sealing,

flocculation.- Local processes of carbon and sulphur cycles, in polluted

aquatic medium and treatment systems.- Chemjstry and role of iron and manganese (and other metals)

in the exchange of pollutants between water and sediments innatural and contaminated media. Role as a factor limiting algalbiomasse

- Methods of estimating the polluting load of industrial orurban waste water.- Organic matter / oxygen / nutrient pollution modelling (02,

BOO,' nitrogen, _phosphorus), in town and industry; transport,treatment, and eutrophication.

The effectiveness of the .Volleinweider-OECD model must Obe.checked in the humid tropics. Cullens (1987) mentions three major

45

problems that must be resolved :* The validity of the nutrients / chlorophyll /groups of

phytoplancton/biomass relationships for turbid and non clearwaters,

* The sensitivity of the model to its assumption of constantsedimentation in turbid and variable systems,

* Better estimates of inflows of phosphorus from non pointsources on a stochastic basis rather than the approach of usingannual means,

* Role of external loads.* Equipment needs for successful mechanical control of

macrophytes infestation.

4.4. Health aspects of organic substances,phosphates, in water.

nitrates and

4.5. Tvoes of preliminary studies to choose technical options oftreatment systems." Management of waste water treatment (cost,

Ofinancial help, etc ... ).

4.6. Institutional problems and specialized staff for sanitation,waste water disposal and treatment (technical attendance andconsulting).

. 1

13. INDUSTRIAL MICROTOXICS AND CHEMICALS CONTROL,

1. General causes of pollution

Microtoxics and chemical pollution comes mai~lY from theindustry, but in sorne cases, can also originate fromnatural alteration and erosion. The sources of the toxics,specially those of natural origin, are not always identified.In Kenya for instance (Kilani, 1989), high fluoride contents indrinking water, closely related to the characteristics of theaquifer of each area, are one of the major water qualityproblems. Industrial pollution in the humid tropics, ~s inthe rest of the world, is characterized by the diversity~

the effluents and the toxicity, as well as the variability ofthe waste quantity. Each type of industry has its own technicalprocesses that lead to typical waste water ~and solid wastes,related to its production and subproducts .. The degree of conta­mination varies with the degree of development, the type ofprimery material resources and the exploitation technology. Therace for development in the humid tropics is not alwaysfavourable for the installation and control of adaptedpurification technics for waste water. Foreign competition doesnot weight prices for the sale of factories by sophisticatedpurification systems. Therefore, waste water treatments, whenavailable, are often inadequate. Moreover, the desire of settingup factories with the most economic yield cornes along with a

46

flexible application of waste water standards, when they aredetermined by law.

2. Chemjcal characterjstjcs

2.1. Heavy metals such as mercury, lead, zinc, arsenic, manga­nese, copper, tin, nickel, cobalt, iron, uranium (radioactive),and other constituents as cyanide, fluorine, acid, soda, chloridecompounds, etc ... ,are very toxic. Thus priority must be given toto them in water quality control. They originate in miningactivities, metallurgy, tanneries, surface treatments, pulpmtlls, cellulose, wood transformation, etc.... Heavy metalspollution is known only in sorne places in the humid tropics,often near mines.

2.2. Waste oils, by their often uncontrolled spreading, alsocontributes to raise heavy metals levels.

2.3. Pestjcides (organo-halogens, organo-phosphorated), used incellulose, wood transformation and construction, are oftenconsidered as inorganic toxics because of their weakdegradability and behaviour patterns in the aquatic environment.,To those point originated from the industry, are added thoseproceeding in a diffuse pattern from the vectorial andagriculture spreadings.

2.4. Carbon dioxide. chloride fluorjde hydrocarbons and ozone in~ atmosphere. acid rainfall, are serious topics to takeinto consideration by governments, organizations, and theindustry. Although these themes have 50me speculative aspectswith some uncertain conclusions, they have been predicted to haveconsiderable world-wide effects. From the use of chloridefluoride hydrocarbons (CFC) arises the problem of the 1055 ofatmospheric ozone, with indirect impacts on water quality. The'increase in the radiation and temperature will rebound on theplancton, and weed growth, temperature and pH of the water.Likewise, the high disposal of C02, methane and nitrogen oxidesin the atmosphere by the industry (fossile combustibles), theconstant increase of ozone in the troposphere, and the cutting ofthe humid tropical forest, would increase temperatures by thegreenhouse effect. Among many serious bearings, the rising of theocean level would modify in hydrosystems, hydrodynamics andwater quality of inland waters associated with sea water, suchas estuaries, lagoons, coastal and island groundwaters.

The acid smoke and rainfall (N, C02, ozone,the industry are changing many ecosystems and waterat least in the temperate zone.

3.Behaviour in tb§ aguatjc environment

) fromquality,

Even in small degrees, above toxicity threshold standardsin effluents and water, microtoxic and chemical contamination isharmfu1· heavy meta l s ( 1 i ke pest i ci des) , accumu 1ate insediments, flora and fauna, leading to hardly reversible

47

situations. The effects on the aquatic environment and health arenot well known, besides the consequences of accidents andl aboratory experi ences. -

Toxic for microorganisms, these micro-pollutants can becumbersome in a classical purification.

Kinetics of the accumulation depend on the dissolved orparticular form of the constituents, and the characteristics ofthe aquatic environment, notably those of the sediment, physico­chemistry (pH, temperature, salinity) and flow. Reactions, inter­actions, absorption, adsorption (chelate with organic matter,humic acids, detergents), control the patterns of sedimentationor dissolution of the constituents between the water and thesuspended load or sediment. Salinity and pH variations favour theKinetic evolution of the components precipitation ofhydroxydes, carburates, sulfites with alcaline pH; dissolutionwith acid pH or low dissolved oxygen contents due to phosphatusand nitrogen yields (redox potential). These phenomena ofprecipitation-dissolution, due to the variations of the physico­chemistry, are important in estuaries and also for waste waterwith high salinity and extreme pH, which will evolve strongly inthe environment.

The behaviour of toxic components is little known and mustbe studied in specific cases.

4. Standards, analysis and assays

The substances to be controlled are numerous. Thefollowing incomplete list is given as an indication and must befitted to local pollution sources: aldrine, dieldrine, endrine,isodrine, endosulfan, chloronitrobenzene, trichlorobenzene,hexachlorobenzene, chlorosaniline, parathion, benzene, 1.1.1.­trichloroetane, 1.2.- dichloride, chloroforme, pee, phosphatus,ammonium, adsorbable organohalogen compounds.

Accumulation in tropical organisms is not sufficientlyknown, as well as toxicity. Detection must be developed bytoxicity' assays on aquatic mussels (briophytes) and algae,bacteria, zooplancton (daphnies), fish, sometimes on man, andtests of in~ibition of the cholinesterase and mutagenic assays.

A general standard is oftenuseful to estimate toxicitybudgets and calculate tax coefficients. Let us mention thestandard .. Equ i tox'~ .

5. ~ of controlling industrial· microtoxic and chemicalpollution ~ In-plant control, waste water treatment. self­control. specializeq treatment and security system.

The difficulty in eliminating harmful micro-toxic pollutionin the hydrosystems makes comprehensible the need to avoid it asmuch as possible at the source. Prevention is better than cure.Therefore, integration of efficient anti-pollution systems in theconception and, building of production systems is of greatneces's i ty.

5.1. In-plant control

48

New fabrication processes are "being sought after in arderta modify in a positive way the quantity and quality (nature andcomposition) of the wastes, and the characteristics and intensityof contamination (for instance: new-technics for pulp whiting).Technics of "in-plant control" are still being developed,opening the way to a "clean technology", according to localconditions. It is better to avoid leakages than to treat them,for treatments are expensive, while recuperation helps saving rawmaterials. These technics separate water to a maximum, accordingto the phases of manufacture, and use the minimal amounts(eventual recycling) in order to facilitate subsequenttreatments. The dry processes must be researched. Valorization ofthe waste and sub-products is one of the large ways for thefuture.

5.2. Waste water treatment

Infrastructures for waste water treatments must also bedeveloped: physical, chemical, biological processes, activatedsludge, activated carbon, solvent extraction, oxydation, etc ...Recovery of wastes and elimination of leakage in the mainproduct by improving the yield, represent a profit thatcontributes in the long-term to pay for the cost of the specifictechnology.

The methodology of dimensioning and setting upinfrastructures of treatments (pre-treatment, primary andsecundary "treatments) is an important aspect. In the case ofponds and stabilization basins, it can be directly integratedto the hydrosystems. Among al1 the avaib1e systems for improvingeffluents quality, purification of waste seems to remain themost important. In many cases, the treatments can be performedin the urban station.

The problem of the future of the sludge is somethingserious, as in the case of mining exploitations (spreading,stocking, areas and dams).

5.3. Self-control

The times of the "ashamed polluter, cautious polluter" aregone. It is natural to produce, then it is natural to depollute.The manufacturer is the one who knows better what he isthrowing out, notably the peaks and fluctuations. It is necessaryto promote the notion of self-control of disposal and anti­pollution infrastrutures. These may count with discharges­spillways, instantaneous and integrated counting, and continuousquality. of waste, on the site and in the receiving medium(automatic stations on the river). Instantaneous transmission ofdata, allow the modulation of the rejections or to give thealarme This implies the responsibility of ,the factory andtransparency, with technical attendance for a correct set-up androutine functionning, as well as grants, but also taxes. Theprinciple of "the polluter must pay" must be applied at everylevel, as a persuasive basis to the beginning of water qualitycontrol. The bases of the calculation must be higher for toxicitythan for the other parameters. Administrative pressure is a

, .

49

necessary mean. In order to function, the self-control systemmust 1 be'the subject of visits from the responsible services ofthe environment, and the object of a contract between theindustry and the administration. Training of . specialists(industrial and administrative) must be promoted in this field,as well as education of the workers. An inventory of the mainsources of pollution is necessary for micro-pollutants.

Self- control operations, that are most efficient towardshydrosystems, must be privileged.

5.4. Special treatment and security system

In the humidtropics, few measures are actually adopted,to:- Reduce. toxic waste.wate~ effluents, by completing. individual

treatments with specific processes when it isnecessary todestroy harmful wastes.Set-uptreatment centers for special wastes (oily· emulsions,neutralization of acids, solidification of liquid waste,treament of sludge, etc ... ).

- Avoid uncontrolled dumping of harmful aqueous or solid wastesthat are notably damaging to groundwater (discharge of classl, toxic products).

- Prevent accidental toxic leakage. An accident, always possible,can ·annihilat in a moment all the efforts, yet realizedwith much application and money. Efforts must be se~ on thereliability of works that suffer from the lack of preventivemaintenance, spare parts, specialists in this field. Securitysystems can be complex, . but an organization must be planned :detection of leakages, observation basins, retention areas,drainage areas and basins for solid waste, belt of pumpingwells around the factory to prevent the risks of propagation inthe water table, upstream control and alarm wells, watertightgutters, waterproof areas, separative sewers ...

Other types of pollution are due to mining activities, suchas the long-term reaction of sulphur (pyrite, marcassite) in thecuttings, leading to an acidification of the runoff water.

The diphenyl polychlorinated compounds used in themanufacture of plastic materials can also be dangerous aftertheir degradation or incineration, because polychloropiphenylsaccumulate in the food chain. An agreement of the EconomicCooperation and Development Organization (1973) attempts to limittheir produètion .

. Fi na 11 y, . each i ndustry must adapt or fi nd the appropri atetechnics, economicallY bearable, to control its own wastes.Systems against pollution must be conceived and built at thesame time than production systems .

. In the humid tropics, the different cases of microtoxicpollution, allthe works to improve it and the advances, withspecial attention to the consequences for the hydrosystems, couldbe classified according to the types of industry . .

5.5. Control ofspecific toxics with global bearings, ---Assessment of diverse predictable impacts of .the loss of

atmospheric ozone, greenhouse effect, and acid rainfalls, onwater quality, must be carried out in order to anticipate generaland local concerns. International policy measures must continueto be taken urgently concerning spreading and disposal of theincriminated products.

6. ~ Qi natural chemical substances control in dr;nking water

The problem of high fluoride content is an example.Mentioned by Kilani (1989) as a major issue of water quality inthe Rift Valley, and Kenya in particular, because of sorne adverseeffects in human health, investigation is currently under way inthis country to develop a technically feasible, cheap and simplemethod to reduce fluoride levels in drinking water: use of claypots, activated alumina, bone charcoal and alumflocculation.Activated alumina shows the highest fluoride removal capacity.The WHO standard of fluoride content, not more than 1 mg.l-1,has been found to be too difficult to attain in rural watersupply.

14. INDUSTRIAL THERMIC POLLUTION

Thermic and atmospheric pollution is largely due to the­industry. Thermic sources are generally power generation,industrial cooling, and geothermal power plant. The increase oftemperature in the receiving medium is generally of littleextension in the humid tropics, but research on the use ofhot water (aquaculture, greenhouses, for instance) must .. bedeveloped for specific projects.

15. WATER QUALITY CONTROL RELATED TO LAND MANAGEMENT

Deforestation! land management on large areas or riverbanksand mining exploitation, increase erosion and, the turbiditv andsedimentation in streams and lakes. Organic effluents can act inthe same manner. Thus, the weaker penetration of lightdisminishes photosynthesis of weeds and : phytoplancton~

Sedimentation of the suspended load modifies' the physico­chemistry of the bottoms, disturbs gas exchangeswith plants andanimals (fish), limits growth and reproduction 'at :differentlevels of the food chain. Suspended matters absorb microt6xicswhose effects can be more harmful, depending on the m;neralogy ofthe particules (clays). These phenomena should be investigateddeeply.

Deforestation!land management modify saltsand nytrients

51

cycles and balances, from rainfall to stream. This importantaspect should be studied in the framework of an eperimentalwatershed management for exploitation of humid tropical mediums.The same is true for the management of irrigated perimeters,where natural salts and nutrients cycles are very mùch. modified,with the risk of salinization.

Reuse of waste water in agriculture is of majorimportance. standards and control are the crucial issues to beinvestigated in specific cases (WHO, 1989 ).

16. WATER QUALITY CONTROL RELATED Ta WATER MANAGEMENT

BOO,

ortobe

(fillingrelatedhave to

Various kinds of water management have been previouslymentioned as means of pollution control. Water quality is alsogenerally changed by other water managements such as reservoirs,irrigated areas, channels for transport or drainage, intensivepumping, exploitation of quarries.

The strongest physical, chemical and biological impactsappear with the creation of man-made lakes, and the drainage offlatlands, in the area itself and downstream. So as to minimizedestruction of aquatic ecosystems and degradation of waterquality, multidisciplinary studies are required, at the designstage, and at each step of the projects, over the tens of yearsthat are often necessary to reach new steady-states.

The effects of progressive river regulationdrying), and the new regime of the hydrochemistry,1eve l sand di scharges, in the area and downstream,progammed according to diverse issues:

Biodegradation of the previous vegetation highliberation of nitrogen compounds and toxic substances

- Biocenotic changes, including* development of vectorial endemics (insects, gasteropods,

larvea), favoured by man migration, and accumulation oforganic matter. It is necessary to establish ecologicalguidelines for the disease vectors, building, and hydraulicworks for the design of water storage and drainage, in orderto minimize the danger (see chap. 10).

* Abnormal development of macrophytes, plancton and toxicalgae. Water management modifies the ecology of plancton andmacrophytes. It may favour the occurrence of nuisance speciessuch as toxic algae (cyanobacteria Microcystis and Anabaena).Factors with regards to succession and growth at bothcellular and ecosystem levels (N/P ratio, iron, climate ... ),must be assessed in the framework of the study of variousgroups. Toxins should be detected and methods developed toremove or inactivate them. The role of riparian vegetationand buffer strips in stream, lake and flatland, in protectingsurface water quality should be investigated more, as well asthe organic vegetal matter cycle.

- New dynamics and chemical kinetics. Reduction of the flushingeffect of minor flood events. Evolution of the stratification

52

02, temperature; anoxy of the hypolimnic water, occurrence oftoxic substances such as hydrogen sulphide, euphotic surfacelying, dynamic changes related to yields and meteorologicalconditions.

- Central or downstream modification of the leaching by thefloods of soils, ponds, riverbanks, wetlands.

- Increasing pollution (bacteria, toxics, eutrophication) due toconcentration of population and new activities,allowed in thearea by water resources management.

53,

REFERENCES

-AlABASTER J.S.. 1981. Review of the state of aquatic pollutionof east African inland waters. CIFA Occas. Pap., 9, 36 p.-ANONYME, 1971. Standard Methods for exa~ination of water andwastewater. A. P.H. A. AWWA-WPCf. Amer ican Publ ic Heal thAssociation, Inc, 13th Ed.-ANONYME, 1915. Directives du conseil des cOMmunautés européennesconcernant la qualité des eaux de baignade. 8 dec. 1975.-ANONYME, 1976: Directives du conseil des cOlMlUnautés européennesconcernant la qualité des eaux superficielles destinées à laproduction d'eau alimentaire. 16 juin 1975.-ANONYME, 1977."Drinking water and health. National ResearchCouncil, Washington, OC, National AcadelllY of SCiences.-ANONYME, 197B. Hater quality surveys. Aguide for the collectionand interpretation of water quality data. Prepared by IHD/ WHOworking group on the quality of water - UNESCO.-ANONYME, 1979. Paral8étres de la qualité des eaux. Ed. Ministérede l'environnellent et du cadre de vie, Paris, 259 p.-ANONYME, 1983. Ali.entation en eau de petitescollectivités. Technologies appropriées pour les petitesinstallations d'alillentation en eau dans les paysen voie de développeœnt. Centre de Forllation Internationaleà la Gestion des Ressources en Eau-France. Doc. Tech. No.18. ,350 p., Lavoisier, Paris.-ANl»lYME, 1985. National Environllel1tal Protection Council. ThePhilippines EnvironlE!llt Report 1984-1985.-ANONYME, 1986. Guo P.H., 1986 Hater Quality Management in thePhilippines, Assignment Report as Adviser, WHO Hestern PacificRegional center for the proeotion of Environaental Planning andApplied Studies (PEPAS).-ANONYME, 1986. State of the Environment. Ministry of theEnviron~nt. France. 116 p.-ANONYME, 1988. Environll!!l1tal I1anagelleJlt Bureau , PhilippineStrategy for Sustainable Development.-ANONYI'l - oMs. 1986: 'Directives de qualité pour l'eau de boisson.OMS. 'Genéve. ./-ANONYI'( - SUU, 1975. Assainiss_t et drainage de la villed'Abidjan. SETU, Rep. Côtè d'Ivoire.-AUSTRAlléH WATER RESOORCES COOHCIL , 1988.' Proceedings of theNational Workshop on Integrated Catchment Management. University

'of Melbourne, 'May, AWRC Conference Series, No. 16., VGPO.-AZIZ l'I.A., 1981.' Some public health aspects of water supply andwastewater disposai in hot'cliMate countries. Proc. 9th FederalConventional of Austration Hater and WasteHater Association,Institution of Engineers. Australia, April 6-10.-AlIZ l'I.A., 1986: ' certain aspects of water quality lIOOitoring.

Proc. Int. Conf. Hat. & waste. Mgt. Asia, Singapore, : 124-137.-BAOER J.C .. DELfIEU G.. KOUOJOV A., 1987. Etudes hydrologiques~ées dans le cadre du programme de lutte contre l'onchocercose.Etalonnages des stations hydrolétriques du Nord Togo. Campagne1986. Vol. l, ORSTOH, Lomé , 81 p.-BADER J.C., DELFIEU G., KOUûJOU A., WOME K.A., 1987. Etudeshydrologiques llenées dans le cadre du progralMe de lutte cOl)trel'~~chocercose. Rapport final de la campagne 1986. Vol.2, ORSTOM,

, \LOAIe, 50 p.-BAKER R.M., SINGlETON F.L., AND HOOD l'I.A., 1983. Effects ofnutrient deprivation on Vibrio cholerae. Appl. Environ.Microbiol. 46:930-940.-BMBAllAS S., 1986, Monitoring natural waters for drinking-waterauality. WHO Stat 0, 39:32-45.-BENAVIDEZ C.F., 1988. Influencia de los calbios en el uso deisuelo sobre el escurriliento y la erosion en la cuenca dei RioPirai - Alazonia andina, Bolivia. Publ. PHICAB, tesis UMSA, LaPaz. 241 p.-BENSON N.R. et al., 1971. Photolysis of solid and disolveddieldrin. J. of agri. and food chel., 19:66.-BIALKOWSKA-HDBRlANSKA H.. 1987. Detection of enterotoxigenicEscherichia coli by dot blot hybridization with biot inylated DHAprobes. J. Clin. Hicrobiol. 25:338-343.-BISWAS A.K.. 1978. Hater developlllent, supply and A1anagetlE!nt.United Nations Water Conference. Pergallon Press, 217 p.-BOCKEtulL J., 1985. Epidelliology, etiology and laboratorydiagnosis of infectious diarrhea diseases in the tropics. Imm.Infekt., 13:269-275.-BDNDE G. J., 1977. Bacterial indication of Hater pollution.Adv. Aouatic Microbiol. 1:273-364.-BOURRIER R. 1985. Les réseaux d'assainissement. Lavoisier484 p.-BREI'OlD R., PERROOON C.,'1979. Paramétres de la qualité des eaux.Ministére de l'environneMent et du cadre de vie, France, 259 p.-BROCHE J., PESCHET J.L" 1983. Enquete sur les pollutionsactuelles et potentielles en Cote d'Ivoire. ORSTOM IMJltig.,1l3 p.-BROCKMANN CL, 1986. Perfil Awiental de Bolivia. La Paz,Bolivia, llbp.-CATALAN l.D., and ALFONSO P.J., 1973. Effects of HeatedEffluents on the Hater Quality Biota of Laguna de Bay.Proceedings, First Regional 5eIIinar on Philippine EcologicalProblels, Davao City, OCtober 1973, National Research Council ofthe Philippines,: 108-129.-CHANTRAINE J.M. et DUfOUR P., 1983., Reseau nationald'observation de la QUalite des eaux Ilarines et lagunaires en

54

Cote d'Ivoire. Doc. Min. Environ. Francais et Ivoirien.Mtig., 452p.-CHIA L.S: Ed., 1987. Environ.ental Manageaent in Southeast Asia:directions and current status. Faculty of SCience, NationalUniversity of Singapore, 1987.-CllCANAP M., DUFOOl P, 1982. L' assainisselDent de la

,ville d'Abidjan. Evaluation, recOGmandations et propositionsd'alternatives. Ministére de l'EnvironnelBent-ORSTOl1,Paris, 300p.-CllWELL R.R., BRAYTON P.R., GRIMES D.J., ROSIAK D.B., HW S.A.and PAlMER L.H., 1985. Viable but non-culturable Vibriocholerae and related pathogens in the environlent: ilplicationsfor release of genetically engineered licroorganiSlS.Biotechnology, 3:817-820.-ctlLEN P., 1987. A Review of Research ~rtunities inHater Quality, National Water Research selinar, Discussionpapers, AtlWtC, DRE, 5eptelber, :81-99.-DANGERFIELD B.J., 1983. Hater supply and sanitation indeveloping countries. Inst. Water Engineers & SCientists,London.-DAPPEN G., 1976. Pesticide analysis frlll urban Storl run-off.Springfield, Virgine. Departlleflt of the, interior, report NO.PB­:238-593.-DEBATISSE M.L., 1988. Industries du sucre et aftIidons.Lavoisier, 162 p.-DEJlXJX C., 1979. Recherches prelilinaires concernant l'action deBacillus thuringiiesis israelensis de Barjac, sur la fauned'invertébrés d'un cours d'eau tropical. 'rrrlO/VBC/79, 721, Hp.-DEJlXJX C., 1985. Incidence des pesticides dans la pollution deseaux continentales africaines. Verh. Internat. Verein. Lianol.,22: 2452-2456.-DEJlXJX C., 1988. La pollution des eaux continentales africaines.ORSTOM , Paris, 513 p. '-DEON J. ,1982. Mise en valeur des ressources hydriques etsanté. Bibliographie selective. IrIlO/POP/ 82.2, HtlTIG. : 117 p.-DESCHIENS R.,1970. Les lacs de retenue des grands barrages dansles régions chaudes et tropicales, leur incidence sur lesenderties parisitaires. Bull. Soc. Path. exot., 63, 1 : 35-51.-DESJARDINS R., 1988. Le traitement des eaux. Ed. de l'EcolePolytechnique de Montreal, 384 p., Lavoisier, Paris.-D'ITRI F.M., AGUIRRE M.J., and ATHIE L.M., 1981. MunicipalWastewater in Agriculture. Acade.ic Press, New York.-0lf00l P., 1982. Influence des conditions de lilieu sur labiodegradation des latiéres organiQUes dans une lagune tropicale.Oceano. act., 5,3,:355-363.-DUFOOl P., HAOOER O., 1979. Pollution organiQUe et

--eutrophisation eu .ilieu tropical sauaatre. Biologie-EcologieI1editerranéenne, 6,3-4, p. 252.-ECKENFELDER H.H., 1970. L'eau dans l'in~jstrie. Pollution,traitelent, recherche de la qualité. Techn. et Doc., Lavoisier,332 p.

-ECKENFELDER H.H., 1982. Gestion des eaux usées urbaines etindustrielles. Caractérisation, Techniques d' épuration, Aspect~éconOlllique. (Traduit de l'aillericain), 520 p., Lavoisier, Paris.-ECKENFELDER W.H. Jr., 1980. Principles of Hater QualityManagel€nt. CBI Pub. Co. Inc., Boston, Massachusetts.-EDELINE F., 1988. L'épuration biologique des eaux résiduaires.Théorie et Technologie. CEBEDOC, 304 p.• Lavoisier, Paris.-EDWARDS C.A., 1975. Persistent pesticides in the environaent,20. ed. C.R.C. Press, 170 p.-EICHELBERGER J.H., LICHTENBERG J.J., 1971. Persistence ofpesticides in river water. Environaental SCience and Technology,5:541.-EL HINNAWI E.E. 1 1980. The state of the Nile environment : anoverview. Hater SUpply Manage., 4, 1-11.-ELI'ENOOOF M., 1987. Water QUality and WOIIeII in Slall systelS.Proc. Int. SYlp. Slall Sys. Hat. SUp. & Haste. DisposaI,Singapore, :131-141.-ENTl B.A.G., 1980. Ecological aspects of Lake Nasser - Nubia.The first decade of its existence, with special reference to thedeveloplleflt of insect populations and the land and watervegetation. Hater SUpply Manage., 4: 67-72.-ENVIROHI'ENTAl HEAlTH DIVISION, 1986. Departaent of Health.Review of Hater Quality Monitoring in Thailand.-ENVIRlINI1ENTAl HEAlTH DIVISIlIl, 1986. Departilent of Health.Manual on Design, Construction, Operation and Maintenance' ofUpflow Anaerobic Filter TreatAlent System for Hospital Wastewater.Report 5 IDRC, Decelllber.-EVISlIl L.M., 1988. C~rative studies on the survival ofindicator organiSis and pathogens in, fresh and sea water.Proceedings International Conference on Hater and WastewaterMicrobiology, Vol. 2:50 (H), Newport Beach,california. .-EVlSON L.H., JAKES A., 1977. Microbiological criteria fortropical water quality. Hater Hastes and Health in Hot Cliaates,ed. R. FeacherA, H. HcGarry, and D. Mara, :30-51, New York, J~

Hiley.-FEACHEM R.G., 1977. Infectious disease related to water,supplyand excreta disposaI facilities. AlAbio., 6:55-58. , ""-FEECHEM R., l1c GARRY H. and KARA D. (eds),: 1977. Hater,Hastes and Health in Hot Clilates. John Wiley &Sons, London."-FUJIOKA R.S., SHIIUMURA L.K., 1985. Ciostridiul perfringens:' areliable indicator of streaJ water quality. J. 'water. PolI.Control Fed. , : 986-92. Abstracts of the 83rd Annual Meeting,Allerican Society for Hicrobiology, 6~H March 1983,New orl~ans,Louisiana,: 271. ':-", .':, "-FUJIOKA R.S., TENNO K. and KAHSAKO 'S.,;: 1988." Naiürallyoccuring fecal coliforlS and fecal streptoCocci in Hâwaii'sfreshwater streams. Toxicity AsseSSllent: 3:613-630.', ,.' .' ,-FUJIOKA R.S., HASHlHOTO H.H., SIHAK' LB: .ànd YWlG R.H,F.,1981. Effect of sunlight on survival'of indi~tor 'bacterià inseawater. Appl. Environ. Microbiol., 41:690-696.

55

-GARttAH E.E.J., 1983. Part i: Water lluality Issues in Australia,Irlater 2000; Consultants Report No. 7, Water Quality Issues, DRE,AGPS, Canberra, 1983.-GAOOET J.J., 1979. Aquatic l'leeds in Mrican man made lakes.PANS,25,3:279-286.-GAUTIER H., PEPIN Y., ETIENNE J., LAPETITE J.H., 1987.Installation de balises Argos/Chloé de télétransmissiondes données hydrologiques en Guinée et Côte d'Ivoire. -Rapportde mission de pose de 25 balises en Côte d'Ivoire, Guinée etBurkina Faso du 7 ilIai au 10 juin 1987. ORSTOM - OMS - OCP.Montpellier, 69 p.-GEORGE T. T.. 1975. Watar pollution in relation to aquaculture inSudan CIFA - Technical paper No.4 , supp P. 1: 753-763.-GEORGE T. L, EL HOGHRABY A. I., 1978. Status of aquaticpollution in the Sudan, its control and protection of the livingresources. Sixth FAO/SIDA workshop in Aquatic pollution inrel?tion to protection of living resources, PIR;TPLR/78/Inf. 20,IlIUltig., 23 p.-GIAMBELLUCA T.W., 1986. Land-use effects on the water balanceof a tropical island. Natl. Geogr. Res., voU, :125-51.-GIDDA A., LE BARBE L., BAOER J.C., 1988. Jaugeages,télétranSlRission et traçages : élélllents pour une stratégie contrel'onchocercose (Afrique OCcidentale). Résumé Congrès Mondialdes Ressources en Eau de l'AIRE, Ottawa, Canada, 28 lai au 3 juin1988 :274-277.-GIRARD G., 198B. l1odélisation conjointe du cycle de l'eau et dutransfert des nitrates sur un systéllle hydrologique. JournéesHydrologiques ORSTOM, Montpellier, 25 p.-GIRARD G., MORIN G., CHARBONNEAU R., 1972. Modeleprecipitations-debits a descretisation spatiale. Cah. ORSTOM,ser. Hydrol., IX,4:35-52.-GOVERNMENT OF THAILAND, 1989. Thailand Country Profile onDrinking Irlater Supply and Sanitation. Harch.-GMR A.H., 1980. Water Quality in Catchflent EcosystelRs. JohnNiley. Ed., New York, 335 p.-GUYOT J.L., HERAIL G., 1989. Hining operations and lIIOdificationof the physical chellical nature of the waters of the Rio Kakadrainage basin ((vides, Bolivia). SedilllBnt and the envirOllent,IAHS Third SCientific Assefllbly, BaltillOre, MaY,IAHS Publ. 184 :115-121.-GUYOT J.L., ROCHE H.A., and BOURGES J., 1988. Etude de laphysico-chiRlie et des suspensions des cours d'eau de l'Ailazoniebolivienne : _l'exellPle du Rio Beni. Journées Hydrologiques del' ORSTOM, Hont peIl ier, septembre.-GUYOT J.L., ROCHE M.A., NORIEGA L., CALLE H., QUINTANILLA J.(in press). Salinities and sedillent Loads on the BolivianHighlands. J. of Hydrology,Elsevier.-HAOlEY R.F., 1986. Long-terM lOOitoring of natural and lan-ladechanges in the hydrological regile and related ecologicalenvironmental Project IHB - II. A.3.1., UNESCO.

-HALEN LC. , 1988. Fecal coliforlAs as indicators in tropicalwaters: a review. Toxicity Assessment. 3:46H77.-HALEN Le.. 1989. Tropical Source Water. Savannah Ri verl.aboratoY,Aiken, South Carolina, 16 p.-HALEN LC., SANTIAGO-MfRCAllO J., TORANIOS G.A., andBERI1UOES M., 1987. What does the presence of fecalcolifor.; indicate in the waters of Puerto Rico? AReview.Bol. Puerto Rico Med. Assac .. 79:189-193.-HERVOUfT J.P., 1983. Aménagement hydro-agricole et onchocercose:Loumana (Haute-Volta). in: De l'Epidémiologie à la GéographieHUlllaine, Travaux et DocUileotS de Géographie Tropicale No. 48,éditions ACCT/CNRS, Paris,: 271-276.-HIGHTOH R.B., 1970. The influence of water conservation scheaeson the spread of tropical diseases in Kenya. E. Afr. IIled. Res.Council, Scientific Conference, Nairobi, Jaun., 4 p.-HA E.O. and PETR L, 1983. Selected bibliographyon Il!ajorafrican reservoirs. CIFA, occ. pap. No.lO, 53 p.-JAMtS A., 1984. An introduction to Water Quality Modelling.J. Wiley, April.-JII'IENEI L., MUiHl I., TORANlOS G. A., and HALEN LC. , 1989.The survival and activity of Salronella typhilUriUla andEscherichia coli in tropical freshwater. J. Appl. Bactèr io1.-JONES G.P. (ed.), 1982. Ilproveaent of aethods of long-terlprediction of variations in groundNater resources and regimes dueto hUfian activity. IAGS Publ. NO.I36.-JOOOAN P., lINRAU G.O., BARTH(lMW R.K., COOK J.A., andGRIST E., 1982. Value of individual household water supplies inthe lIaintenance phase of a schistosOllliasis control prograMe inSaint Lucia, after chellOtherapy. Bull. WHO 60 : 583-588.-JlINKIN MC., 1979. POItpes à Mins destinées àl'approvisionnetent en eau potable dans les pays en voie dedéveloppllent. Doc. Tech. No.lO, Lavoisier, Paris, 266 p.-KACWl C. 1 SAL TER E.F., 1979. Environmental pollution in laabîa.In·Praceeding of the national seminar on environlllBntal anddeveloplllent, Lusaka, ed. D.S. Johnson and W. Roder, OCcas. Stud.,

. '"lalDbla Geogr. Assac. ,10:IBI-216.-KELLER R. (ed.), 1983. Hydrology of Hu.id Tropical Regions.IAHSPubl. No. 140, Hamburg SYMPOsium.-KINAWY Ll., EL CHA/'tR O.A., 1973. SOlle effects of the highdam on the environment. Il eijE, Congrés des grands barrages,Madrid, 1973, Q 40, R59: 959-974.-KDVOA V.A., 1973. Irrigations, drainage and salinity. AIlinternational source book, Hutchinson PUblishing Group, London,FAO.-LAMB J.C., 1988. Water quality and control, J. Wiley, New York.-LARAQUE A.. 1988. L'évolution hydrochilaique de retenuescollinaires du Nordeste brésilien . Journees Hydrologiques œSTot1de Montpellier ,septelftbre, 19 p.-LAU L.S., CARPENTER R.A., DOW M.A., 1984. Nater pollution: AChinese perspective. Natural SysteJS for DevelDPllent. ed. R.A.

56

Carpenter, chap. 8: 388-431, New York, MacMillan.-LAU L.S., MINK J,F., 1986. Indentifying and correcting organicchelRical contamination of groundwater sources: A learningexperience. Proceedings, American Water Works Association 1986Annual Conference, Denver, Colorado.-LE 8AA8E L., \GlOOA A., 1987. Epandage.d'insecticides dans lesrivières. Portées et dosages optimae. ORSTOM , Montpellier, 17 p.-LE BARBE L., GlOOA A., DELFIEU G., ROME K.A., 1987. Etudeshydrologiques lAenées dans le cadre du programme de lutte contrel'onchocercose. Etude expérimentale de la propagat ion desinsecticides dans les rivières. Rapport final. ORSTOM , OMS, OCP.Montpellier. 184 p.-LESEL R., LANDRAGIN G., K!X.Z H., 1979. La biadetection.Agence Financiere de Bassin Rhin-Mense, 6 p.-LEVEQUE C., BURTON M., 1981. Fishes. In: "The ecology andutilization of African island waters·. Ed. SYllloens, Burgis andGaudet. UNEP, Nairobi. :69-79.-LOINTER M., ROCHE M.A., 1988. Salinités et suspensions desestuaires de Guyane. Méthodes et résultats. JournéesHydrologiques ORSTOM, Montpellier, septembre, 32 p.-MAASHALL B.E., FALCONER A.C., 1973. Eutrophication of a tropicalAfrican inpoundment (lake Mc Ilwaine, Rhodesia). Hydrobiologic,43,1-2:109-123.-MARTIN M., 1977. Devenir des polluants organiQUes daus le iIIilieunaturel en fonction des traitements et par rapport aux cycles de'lie de ces produits. (PŒ, pesticides, agents de surface). Univ.Rennes:-- Journées de Montpellier, Coll. Recherche Environment,no 8.-MASSCHELEIN W.J., 1988. L'ozonation de l'eau, manuel pratique.Lavoisier, Paris, 240 p.-MATHUR S.P., and SAHA J.G., 1975. Microbiologic degradation oflindane C-14 in a flooded sandy loall soil. Soil science, 120:301.-McKENDRICK J., 1982. Water supoly and sewage treatment inrelation to water quality. Monogr. Biol. , 49:201-217.-MENDOZA G.G., 1989. Abastecillliento de Agua Potable a los C~ntros

Urbanos e Industriales. Presented in Querétaro, Cro. Febrero.-HERRICK J.H., 1985. The effect of pipes water on early childhoodIllOrtality in urban Brazil, 1970 to 1976. DelDgraphy 22: 1-24.-MILLS H.B. et al., 1982. Water Quality assessment: a screeningprocedure for toxic and conventional pollutants. Document No.EPA-600/6-82-004a.-MOORE G., CHRISTY L., 197B. Legislation for control of aquaticpollution. Part 1. International aspects. Sixth FAO/SIDA Workshopon aquatic pollution in relation to protection of living,resources, FIR:TPLR/78 , 6:1-12.,~OZ C., 1981. UNEP'S related activities on the internationaldrinking water supply and sanitation decade. UNEP report, firstjoint FAO/UNEP/WHO Panel of Experts on Environmental Managillentfor Vector Control, Géneve, III(fltig,: 9-11.-NATIONAl RESEARCH COUNCIL, 1982. Ecological aspects of

developllent in the humid tropics. Washington, D.C., NationalArademy Press. lASS.-NGDTLE M.A.K., CHALLE A.E., HAPLIHDA R.R., 1987. Aquatic['Dilution in Tanzania. 6th. FM/SIDA Workshop on aquaticpllllutlOn in relation ta protection of living resources,FIR:TPLR. 78/19, IllUltig., 9p.-NGUNYA LA., 1975. Some adrlÏnistrative aspects of establisling apollution control organization in a developing country. Progressln water technology. 7,2:83-91.-NOBLE R.G., HEMENS, J. , 1978. Inland water ecosystelRs in SouthAfrica: a review of research needs. S.Afr. Nat. sei. Progr. Ref.34, 150 p.-NOBLE R.G., PRETORIUS W.A., CHlJfTER F.M., 1971. BiolO9icalaspects of water pollution. Suid Afrikaanse Tydskrift virWetenskap: 132-J36.·NONGlUK TUNYAVANlCH, 1989. Water SUpply and Water User Behavior:The Use of Cement Rainwater Jars in Northeastern Thailand.Thai land-Austral ian Nor theast Vi lIage Water Resource Project,Report No. 134. June.-OI.UWANDE P.A., SRIDHAR K.C., 8AMMEKE A.O. and ~UllAOEJO

A.O., 1983. Pollution level in some Nigerian rivers. Water Res.17:957-963.-ONG S.E., 1987. Water pollution control in Singapore ­historical development and future prospects. Proc. Int. Symp.S.all Sys. Wat. &Haste. Disposai, Singapore, : 15-25.-OHGWENCY G.S.O., 1973. The significance of the Geographie andGeologic factors in the var iation of Groundwater ChelRistry in~enya. M.Sc., Univers. Nairobi.-OREKOYA T., 1978.0il oollution abatment. Getrie FAO/SIDAWorkshop on aquatic pollution in relation to living resources.Nairobi and Mombasa, llIultig.,: 102-112.-ORLOB G. T., 1986, Mathelliathicai Modelling of water Cuality(Streams, Lakes and Reservoirs). Ed. J. Wiley. ~

-PAHSWAD T., POLPRASERT C. and YAMAMOTO K. (Eds)., 1988.Water Pollution Control in Asia. Proc. 2nd lAlr/PRC AsianConference Ofl Hatér Pollut ion Cootrol, Bangkok. Thai land, :9-11,Hoveinber,-PESCOD M. B., 1977. Surface ilater QUali ty cri ter ia for tropicaldeveloping countries. Water, Hastes and Health in Hot CliMates.ed. R. Feachelll. M. McGarry, and D. Mara, :52-72, New York ,JohnWiley.-PESSON P., 1976. La pollution des eaux cootinentales. Incidencessur les biocénoses aauatiques.Gauthier,villars Ed., Paris, 285 p.-PHILIPPON B., MOUCHET J., 1976. Repercussions des aménage­ments hydrauliques à usage agricole sur l'épidémiologie desAlaladies à vecteurs en Afrique intertropicale. In" Cahiers, daCENECA", Doc. 3-2, 13, IIIIJltig., 14 p. ,"'" , .'-PIMtNTEL D., 1971. Ecological effects of pesticides on non­target species. Publ. Executive Off. of the President Off., ofSci. and Techn., Cornell Univ., 220 p. .' .~~; '.' '.

57

-POUYAOO B., 1987. TélétranSlflÏssiOil satellitaire au servicedu progralll! de lutte contre l'OIlchocercose en Atr iQUe del'OUest. Colloque sur la telemesure et la translllissiOil desdOIlnees en hydrologie, 23-27 mars, Toulouse, 5p.-POUYAUD B., LE 8ARBE L., 1987. Onchocercose, hydrologiQUes ettélétransBlÎssiOll, Water tor the future: Hydrology in perpective.proceedings of the sY18posiulR, April, ROAle, IAIlS :239-244.-PROST A., 1986. The burden of blindoess in adult males in theSavanna villages of West Africa exposed to OIlchocerciasis.TransactiOils of the Royal Societ of Tropical Medicine and Hygiene'80: 525-527.-PROST P.., 1989. The management of Water resources, developmentand human health . Internat. Coll. in the Development ofHydrologic and Water Manage~ent Strategies in the Humid Tropics,UNESCO, Townsville.-PROST A. and PRESCOTT' N., 1984. Cost-effectiveness of blindnesspreventiOil by the Onchocerciasis COiltrol Prograllllle in UpperVolta. Bull. WHO, 62: 795-802.-PROST A. and VAUGELAOf J., 1981. La surilOrtalité des aveuglesen zOile de savane ouest-africaine. Bull. WHO, 59: 773-776.-QUANO E.A.R., LOHANI B.N. and THANH H.C. (eds). , 1987.PollutiOil COiltrol in Developing Countries. Proc. InternatiOilalCOilference, 8angkok, Thailand, 21-25 February.-RANGELEY W.R., 1985. Irrigation and drainage in the World. Proc.International COilference 00 Food and Water, College statiOil ,Texas, May 26-30 : 8.-RICHARD Y., 1987. Vade-meCUM du chef d'usine de traitement d'eaudestinée â la consommation. AGHTM, Lavoisier, 144 p.-ROBARTS R.D., 1975. Water pollution in Rhodesia. Rhod. SCi.News, 9,: 328-332.-ROCHE M.A., 1972. Traçage hydrochimique naturel du mouvementdes eaux dans le lac Tchad. Sect. Hydrol. ORSTOM, Paris, octobre1972, 10 p., 5 fig., C.R. Symposiulll sur l'Hydrolgie des lacs,A.I.H.S. , Helsinki, septelllbre 1973 :18-27.-ROCHE M.A., 1973. Traçage naturel salin et isotopique des eauxdu système hydrologique du lac Tchad. Thèse de Doctorat ès­SCiences, octobre 1973, Paris VI, 389 p., Trav. et Doc. del'ORSIOM, 1980.:ROCHE M.A., 1975. Geochelllistry and Natural IOilic and IsotopicTracing : Two complellentary Ways to Study the salinity Regille

.of the Hydrological System of Lake Chad. J. of Hydrology, 26,:153-171, présenté Coll. Hydrochillie des eaux naturelles,BurlingtOil (Canada), août.-ROCHE M.A., 1976. Méthodologie de mesure de ,la dynaMiQUe deseaux, des sels et des suspensions en estuaire. C.R.Quatorzièmes Journées de l'Hydraulique, Société Hydrotechniquede France, Question III, rapport 1 : 1-8.-ROCHE M.A., 1977. HydrodynaJIique et évaluation du risque depollutiOil dans un estuaire à marées. Cah. ORSTOM, sér. Hydrol.,XIV, 4 : 345-382.

-ROCHE M.A., 1982. COIPOrte.ents hydrologiques cQlParés etérosion de l'écosystème tropical hUlide à Ecérex , en Guyane.Cah. ORSTDM, sér. Hydro!.: 81"114.-ROCHE M.A. Y CANEDO, M., 1984. Programa Hidrol6gico yClilllatol6gico de la Cuenca AIIazénica de Bolivia. Folleto depresentacion dei PHICAB. Publ. PHICAB, La Paz, offset color, 4p.-ROCHE M.A., ABASTO N., TOlEDE M., CORDIER J.P., POIHTILLARTC., 1986. Mapas de las salinidades de los rios de la CuencaAmaz6nica de Bolivia. PHICAS. 3 hojas offset color. ORSTOM.-ROCHE M.A. and FERNANDEl JAUREGUI C., 19B8. Water Resources,Salinity and Salt ExportatiOils of the Rivers of the BolivianAlaZOil. J. of Hydrology, Elsevier, AlIlsterdalll, 101: 305-331.-SAAO M.A.H., 1980. EutrophicatiOil of lake Mariut. A heavilypolluted lake in Egypt. Int. At~ic. Energy Agency Vienne,:153­163.-SANTO DOMINGO J.W., FUENTES F.A. and HAlEN, T.C., 1989.SUrvival and activity of Streptococcus faecalis and Escherichiacoli in petroleulR cootallinated tropical lIIarine waters.EnvirOil. PollutiOll, 56:263-281.-SCHOll C.R. and OKUN D.A., 1984. SUrface water treatmentfor communities in developing countries. John Wiley and SoIlS,New York.-SCOTNEY N.• 1980.Developing a health educatiOil compOilent for theUNICEF water and sanitatiOil prograBl in SUdan. UNICEF Report,Nairobi, IIUltig., 25p.-SECRETARIA DE DESARROlLO URBANO y ECOlOGIA, 1985. Evaluaci6n deCuencas Hidrolégicas de Acuerdo a su Grado de COiltaAlinaci6n.Direccién General de Prevencién y cOiltrol de la cOiltaMinaciénAmbiental, México.-SERVAT E., 1987. Contribution à l'étude de la pollution duruissellement fluvial urbain. Thése Hontpellier, ORSTOM, 206 p.-SHARMA M.L., 1986. Role of groundHater in urban water supplies ofBangkok, Thailand, and Jakarta, Indonesia. Norking Paper,Environment and Policy Institute, East-West Center, HOilOlulu,123p.-SHUVAl H.!., TIl DEN R.L., PERRY B.H. and GROSSE, R.H., 1981.Effect of investments in water supply and sanitatiOil 00 healthstatus : a threshold-saturation theory. Bull. WHO 59: 243-248.-SIMMON VJ. et al., 1977. Mutagenic activity of chefllicalsidentified in drinking water. Developments in toxicology andenvironlental sci., 2:249.-SMITH L.S., 1969. Public health aspects of water pollutioncOiltrol . Water pollut. Control , 68:544-549.-SMITH A., LOSSEY O., 1981. Pesticides and equiplent requireMentsfor national vector cOiltrol prograll in developing countries.WHO/VBC/81.4,98p.-SOOH C.H., 1982. Pollution Control in Singapore, Malayan LawReview, Vol. 24(2): 213-219.-STEElE T.D., 1987. Water Quality lIlOIlitoring strategies. 1AIlS ,32,2, June.

5&

-STEPHEHSON O., 1988. water and Hastewater SysteMs Analysis.Developlellt in IIater science, Elsevier.-STEllMT B.J. and VERltœVEH T.J., 1987. SUrface Hater ResearchHeeds in Australia, SWCC, rwfRC, PAIrIA, 5eptellber.~STEYH D.J., TŒRIEH DJ., VISSER J.H., 1976. Eutrophicatioolevels of sOlle South African inpoundell!l1ts. Part 3 and 4,Roodeplaat 001. Hater S.A. ,2:1-6.-TtLLlHG J.A. , 1980. SOIIe problelS of aquatic enviroollents inEgypt frOi a general viewpoint of Hile ecology. Hater SUpplyManage. 4:13-20.-TAN T.H. J 1978. Hater pollutioo cootrol. Proc. selinar 00

pollutioo Preventioo and Enviroo;ental Cooservatioo in Singapore,:11-13.-TAY J.H. and OHG S.L. (Eds)., 1986. water and HastewaterManagellent in Asia. Proc. Internatiooal Cooference 00 Hater& Hastewater Managelll!l1t in Asia, Singapore, 26-28 February.-TCHOOANlXlOOS G. and SCHROEDER, LE., 1985. \rIater QualityCharacteritics. I10delling and lIOdificatioo. Benjaillin CUlllllingsPub. Co. Inc., Hew York.-THORTON J.A. , H[)(lU H.K., 1982. The aqueous phase : nutrientsin run-off frOi Slall cachetlents. l1onogr. Biol., 49:71-77.-TllERIEH D.F., 1975. South African eutrophicatioo problel. Aperpectives. Hat. Pollut. Control., 76:136-162.-TROOGILL S. T., 1986. Solute Processes. J. Ir/iley.-lJlESCO, 1964. SCientific proble.s of the hu.id tropical deltasand their illPlicatioo. MaturaI Resources Research, Ho 6.-lJlESCO, 1974. Hu.id tropical Asia. Hatural Resources Research,Ho 12.-UNESCO, 1980. Aquifer contalinatioo and protectioo . Preparedby IHP working Group 8.3, Chair.ain and General Editor:R.E. Jakson.-IJjESCO, 1980. Dispersioo and self-purificatioo ofpollutants in surface water systells. Areport by IHP IlOI'kinggroup 6.1, Chief Editors: P.G. ~itehead and T. Lack.-VtLIRON F., 1986. Héaento de l'exploitant de l'eau et del'assainisse.ent. Lyonnaise des eaux, Lavoisier, Paris, 1040 p.-VAN DER BERG T., 1988. Dairy technology in the tropics and

·subtropics. Lavoisier. .-VAN DIJK J.C. and lJMH J.H.C.M., 1981. La filtratioo lente sursable pour l'approvisiooe&lent en eau collective dans les pays endéveloppelllent. Doc. Tech. Ho. 11. Centre Internatiooal deReférence pour l'approvisioollellent en eau collective etl'assainisselent, Lavoisier ,Paris, 192 p.-VEDRY 8., 1987. L'analyse écologique des boues activées.SEGHEC, Lavoisier, Paris, 120 p.-VERHAAK J.F. , SHANEPIIL J•H. , SCHIDlBEE H.J. , 1981. Thephosphorus cycle in Gerilliston Lake. I. Investigatiooal objectivesand aspects of the lilnology of the lake. Hater S.A. ,7,3:52-57.-VICEHTE V.A. and BECKETT R., 1986. Trace Hetal Speciatioo inLaguna de Bay, Hatural SCiencies Research Institute (Project),

~iversity of the Philippines, Dililan.-HtLDRON H.A., 1975. Health Standards for Heavy !tetaIs. Chell.Br., 11: 354-357 .-WATTS D.G., HANKS R.J., 1978. Asoil water nitrogen 1Ode1 forirrigated corn 00 sandy soils. Soil sci. Sov. AlIl!r. J., vol.42:492-499.-Ir/ElCGME R.l., 1972. The inland water of Africa. Les eauxinterieures d'Afrique. CIFA Tech. Pap. /Doc. Tech. CPCA, 1, 117p.-WHITEHEAD P. G., 1984. The applicatioo of lllathellaticai mIs ofwater quality and pollutant transport: an internatiooal survey .lMESCO . SC.86/WS/10.-WHITTEMORE F.H., 1977. Technical, econOlic and legislativefactors deterillining choice of pesticides for use developpingcountries . Rapp. FOO, WS/D ,8662 , IUltig., 2Op.-WHO, 1970. Fluoride and HUlllan Health. WHO Honograph series,59, Geneva.-WHO, 1989. Health guidelines for the use of wastewater inagriculture and aquaculture. Report of a WHO scientific group.Technical Report series, Ho. 778. WHO publ., Geneva, 74p.-HILSON M.F., HEHDERSOtHELLERS A., 1983. Deforestatioo illPactassesSlent: The problels involved. Hydrology of Hu.id TropicalRegioos, ad. R. Keller, IAHS Publicatioo Ho, 140, HalburgSYlllposiulll : 273-83.