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Technologies for liquid waste management in rural areasBy
Dr S V Mapuskar
Appa Patwardhan Safai Wa Paryawaran Tantraniketan, Dehugaon,Tal.Haveli,
District:Pune, Maharashtra 412109.( INDIA)
I. INTRODUCTION
Waste water management is an important component of sanitation activities. Unless liquid
waste is managed properly, it becomes an important health hazard, more so, in rural areas.
It may be useful to understand the broader perspective of waste management issues relevent
to the Indian scenario, as waste water management forms an important component of the generated
waste. Sustainability and appropriateness of management strategy would be important issues in the
selection of technologies for waste management.
A. Waste Management ProblemGeneration and accumulation of domestic waste for fast growing human settlements is becoming
a major environment and health problem in India. Management of these wastes is, for the present,
very haphazard and inadequate. As a result, such inadequate and inappropriate waste management
has been a major threat to available water resources and to the health status of the community.
B. Conventional Sewerage System
The problem exists in rural as well as in urban areas. In urban areas, methodologies like the
conventional sewerage system etc. which are presently in use, are grossly inadequate to manage
these generated wastes. As a result, at present untreated domestic wastes are finding access to water
resource system or lie untreated on the land surface. This is grossly detrimental to the environment
and to the health of the community, hampering the overall development process.
The prevailing conventional sewerage systems and solid waste management systems which
are in use in urban areas are grossly inadequate for managing the load of domestic wastes from
burgeoning and bloating cities. Due to their capital and operating costs, it is becoming very difficult
to expand or newly establish these systems so as to keep pace with the growth of the cities. Their
operation and maintenance costs also are very prohibitive. Similarly, solid waste management
through the conventional methodologies is also becoming difficult. Hi-tech mechanized processes
are capital intensive and unsuitable for the available manpower.
Further the waste management systems should not be only affluent city dweller oriented. At
present, only about 10% population ( although urban population is 25% ) of the country, which is
residing in the cities, is covered with these conventional systems. Low income urban, periurban, and
rural areas will have to be considered. About 90% of the population is rural and remains uncovered
with these systems. Obviously, it will not be feasible to cover this 90% population of the country
with capital intensive, maintenance intensive, hi-tech methodologies.
In the rural areas, the situation is worst. In these areas, waste management is eithernonexistent or very marginal and haphazard. If we depend on the above mentioned systems, it will
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not be possible to have any appreciable impact on the sanitation and water supply situation in rural
areas.
C. Continuing River Water and Land Pollution
It is noticed that in urban areas covered with conventional sewerage system, the capacity forfinal treatment of domestic wastes is grossly inadequate. As a result, untreated sewage is let out in
the water bodies like rivers or sea. The domestic wastes from rural areas are also finding access to
rivers without any treatment. Natural water purification process is inadequate to take care of such
massive wastes. As a result, river beds are day by day being converted to virtually open sewers. The
problem is compounded by the construction of dams and bunds in the river course. Large river
cleaning projects have been found to be inadequate because these projects are mainly concentrated
on establishing conventional sewage systems in townships along the course of the rivers. Obviously,
limited funds available with them are unable to take in all the burden. Thus various river cleaning
projects are turning into media gimmicks. In spite of the Ganga cleaning project, the Ganga has not
changed much. Similarly, other river cleaning projects mainly concentrate on expansion or
establishment of conventional sewerage systems for limited number of cities and towns on river
banks. Further, pollution from rural areas continues unabated.
D. Terminologies with reference to waste water
It would be necessary to understand the terminologies commonly used with reference to waste
water
Sewage Waste water combined with excreta
Sullage Waste water NOT mixed with excreta
Understanding the difference in these two terms is important for technology selection.In the
conventional sewerage system mentioned above, the excretal flow quantity is diluted more than 20times by mixing it with sullage in order to facilitate the flow of excretal matter through the pipelines.
This increases the load on final treatment facility. This procedure is necessary for the conventional
sewerage system. In situations where it would be feasible to keep excretal flow and sullage separate,
the final treatment for them separately and effectively becomes simpler, easier, cheaper and
covenient.
In recent years, a new terminology is being adopted.
Black water This term is in use for sewage
Grey water- This term is used for sullage
Yellow water This is an effluent from urinals
White water It is treated potable water
Based on the location of final treatment of the waste, the management can be classified as
On site when the final treatment is effected at the place of generation of waste
Off site when the final treatment is effected AWAY from the place of generation of waste.
Wherever feasible, On Site treatment is convenient ,simpler, cheaper and easily manageable.
E. Selection of appropriate technologies for sullage management in rural areas
It is obvious that systems akin to conventional sewage system will not be appropriate for
rural and periurban areas. The selection can be based on the following considerations.
These should be1. Hygienically safe.
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2. Environment friendly
3. Simple
4. Low cost for construction
5. Easy and low cost at domestic and village level for operation and maintenance.
6. As far as possible, should be decentralised ( preferably On Site )
7. Recovery of end products for use
A brief review of some suitable technologies is presented here. In exceptional situations, it
may be necessary for some other alternatives.
II. GREY WATER MANAGEMENT
It is estimated and experienced that about 75% to 80% of water supplied through piped water
supply schemes comes out as grey water. If it is not managed properly, it flows indiscriminately
through habitations and becomes a serious health hazard due to its pathogenicity. In addition, it
provides a breeding ground for disease spreading insect vectors like mosquitoes etc.
Therefore, it will have to be managed in a hygienic way. In a country like India, where water
availability is a problem, it should be possibly recycled and reused.
The treatment methodology should be- such that it becomes pathogen free, does not promote
insect breeding, and at the same time, this water could be recycled and reused.
The choice of technology is a tricky issue. The high cost, high tech technologies will not be a
solution for this problem under the prevailing conditions and situations in rural areas. These
technologies will have to be affordable and manageable at village level and decentralized depending
on the locations and spread of habitations. They have to be environment friendly, low-cost, hygienic,
requiring intermediate or low level construction and maintenance skills available at village level.
These can be either on-site or off site methods, depending on village level requirements.
The grey water in a rural area can be broadly classified as
1. Domestic grey water
2. Community grey water
Therefore, grey water management system can be established at 2 levels.
1. Domestic level.
2. Community level
a. Onsite or community standpost handpumps etc.b. Off site via transport through suitable drainage system.
In a rural area, the major quantity of grey water is generated in a home. When this water leaves
the premises of the house, it becomes community grey water. Management of grey water at
community level is more elaborate as it demands managerial, financial and technological inputs
which need elaborate arrangements.
III. DOMESTIC GREY WATER MANAGEMENT
If grey water is managed at source, in a decentralized manner, by each household, it becomes
a more appropriate proposition. Of course, availability of area/courtyard/land surrounding the housewill be a requirement. It will be an approach where there could be
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ZERO COMMUNITY WASTE orMINIMUM COMMUNITY WASTE.
If this is to be brought into practice, it would be necessary to provide appropriate technologies at
domestic level. These technologies should be low cost, simple, easily manageable by the household
and at the same time hygienic and appropriate from health aspect.
These technologies in order of preference would be1. Kitchen garden with silt and grease trap and with or without piped root zone system.
2. Domestic leach pit
3. Soak pit
1. Kitchen garden with silt & grease trap and with or without piped root zone system.
Kitchen garden is a preferred option because from the garden, the household gets some
consumable produce like vegetable or fruits. However, this will be possible where open land is
available near the house.
If the grey water is clarified before letting it out to the kitchen garden, the garden grows in abetter way. This can be achieved by passing water through a very simple device like silt & grease
trap.
The garden can be irrigated in two ways. Irrigation can be done via underground, perforated PVC
pipes where water will be treated in filter bed material surrounding the pipe, from where it will
directly reach the roots of the plants. In this case, water will not remain exposed. This method would
require maintenance of the pipe and the filter bed.
The other method will be surface irrigation. This is simpler and requires less maintenance. But the
yield could be less and the excess water will remain exposed.
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2. Domestic leach pit
The other method will be surface irrigation. This is simpler and requires less maintenance. But the
yield could be less and the excess water will remain exposed.
If availability of open land is a constraint and quantity of grey water is more, a domesticleach pit would be a suitable option. This will involve some construction costs for the family.
Leach pit is a brick lined circular pit constructed in honeycomb masonry, having a diameter
of apprimately 1 metre. The pit should have a proper insect proof cover. Water should be led into the
pit through a water seal trap, so that insect movement and mosquito breeding is avoided.
3. Soak pit
When the grey water quantity is limited and availability of open land is a constraint, soak pit
would be a very simple and cheap option for grey water management.
For domestic purposes, a cubical pit is dug in the soil with dimensions of approximately 1
metre length, 1 metre width and 1 metre depth. The surfaces of pit walls and the bottom surface ofthe pit make available more surface area for absorption of water in the soil. For giving stability to the
pit and for distributing incoming water to the available surface area, the pit is filled with stone rubble
of graded sizes. At the top, the pit is covered with supporting material like tree twigs or gunny
sacking etc. and topped up with murrum, so that the inflowing water doesnt remain exposed. In the
centre, an inlet with a filter, like grass filled perforated matka is placed, through which water is
allowed to flow in the pit. An important point is, ordinary brick bats or gravel etc should not be used
as filling material because brickbats tend to crumble when wet. In due course, they obstruct the flow
of water towards the soil surface at the sides of the pit. Stone rubble is also more efficient in
distributing water to all the absorbing surfaces.
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IV. COMMUNITY GREY WATER MANAGEMENT
In very compact habitations, sometimes, with wall to wall houses, it may not be possible to
manage grey water at domestic level. In such a situation domestic grey water would be let out from
the house. As a result, community grey water would be formed. It will have to be collected,
channelized and led to open spaces or outside the village for final treatment. Various treatment
options can be used for managing such grey water. In rural areas, in public places like like water
standposts, handpumps, public wells, etc, overflow grey water is generated. This grey water, which isusually cleaner, will also have to be managed properly. Such water can be managed onsite by
adopting suitable technologies.
This community grey water management can be done in four components.
A. Preparing village master plan for sullage management
B. On site management for water from public standposts, wells, hand pumps etc.
C. Collection and transport of community grey water
D. Off site management for drain - tranported community sullage.
A. Village Master plan for Grey Water Management
.It has been a common observation that the sullage management is usually done very haphazardly
without any planning, resulting into uneven, unlevelled, piecemeal drains leading nowhere with
stagnant cess pools in the village at multiple places. This can be avoided if a master plan for the the
sullage management in the village is planned .Geographical situation, land contours, directions of
gravity flow, streets, number of houses streetwise, expected quantity of sullage, location for final
treatment etc are considered while preparing the master plan. Suitable technologies for given
situations will have to planned simultaneouslly. It will have to be a judicious mix of multiple
technology options of domestic and community use technologies. The execution of the plan can
proceed as per availability of funds.
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B. Community grey water-Onsite management.
The following options can be used for on site mangement of grey water from standpost
handpumps etc as stated above.
1. Plantation with intercepting silt chamber.2. Community leach pit
3. Soak away system
4. Root zone system.
1. Plantation
If open land is available near the water points, plantation with the grey water from these sources
would decidedly be a better option. It will be better if water is allowed to flow via silt chamber which
could be periodically cleaned.
2. Community leach pit
When open land is not available, community leach pit could be a technological option. This
option can also be used at the end of drainage lines on which there are a limited number of
households.
This is a brick lined circular pit constructed in honeycombed brick masonry. The diameter of
the pit maybe 5-7 feet and the depth 4-5 feet. Corbelling is done in top portion of the brick work so
that the opening may be reduced to a diameter of about 3 feet. This pit is covered with RCC or flag
stone cover. The water is allowed to get in the pit via silt cum grease trap. This will restrict the
quantity of silt flowing into the pit. At the same time, by acting as a trap, it will avoid passage of
insects and mosquito breeding.
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3. Soakaway channel system
When the quantity of water is more, soakaway channel technology can be used. Functionally, it is
similar to soak pit; however, in this case, the pit is extended lengthwise, extending may be upto 15-
20 feet. The channel is filled up with stone rubble and finally topped up just like a soak pit. Water is
allowed to flow in from one end via a sludge chamber. Water passes through the channel and getsgradually absorbed in the surrounding soil.
4. Root zone system
This is useful for managing grey water onsite. This system can also be useful for moderately limited
community grey water from households. Here, a kind of sedimentation cum filter bed is established
on top of which, plants like reed etc can grow. Micro organisms grow in these beds. Oxygen is
provided by the roots of the reeds, which also take care of the pollutants. The outflowing water from
this system is well stabilized and pathogen free. It can be used for horticulture, etc.
C. Collection and transportation of community grey water
As stated earlier, in very crowded and compact habitations, the management of grey water atdomestic level is not possible due to non availability of land. As such, it will not be possible to
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manage this grey water on site. Therefore, the offsite management options will have to be
considered. Usually, by establishing suitable transportation system, this community grey water is
carried away outside the village, where the final treatment system can be established
Therefore, it is necessary to install a suitable system for the collection and transportation of
sullage upto the final treatment site. Following two systems are usually advised for this purpose:1. Surface drain, 2. Small bore sullage carriage system.
1. Surface drain.
It has been a common practice in a large number of villages.to construct surface drains to
carry away the sullage. Unfortunately, most of them malfunction. Technological causes for this are
common. Cross section of the drain design is very important. The sullage carries silt and suspended
solids with it. Sullage should have adequate velocity for carrying these also. For maintaining
adequate self cleansing velocity, cross section of the drain may be as indicated in the figure.
Adequate gradient or slope is also necessary. Inappropriate size is another factor. The bends in the
drainage lines should be gradual and not at an acute angle.
2. Small bore sullage drainage system
This system comprises of underground relatively superficially laid PVC pipe line of small
bore, with intervening intercepting tanks at every 200 feet and at corners or bends. Pipes have a
diameter of 4 to 6 inches. Connections from households should have nahani trap inside the house and
silt trap outside. Intercepting tank should have tee fittings on both sides and these should be
periodically cleaned.
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C. Community grey water- off site management Final Treatment
For final treatment, some options may be as follows
1. Sullage stabilization pond system
2. Pisciculture ponds
3. Aerated lagoons4. Effluent treatment plant
In consideration of financial and technological resources at village panchayat level, most
appropriate system is Waste stabilization pond system.
1. Waste stabilization pond systemThis system has very low cost, easy for maintenance and the stabilized water outflowing from
the system can be used for irrigation purposes in agriculture, horticulture, pisciculture, etc. In this
system, grey water collected via drainage system is passed through a system of ponds in which grey
water is stabilized, its pathogenecity is reduced and the stabilized water becomes usable for
irrigation. The grey water is stabilized in these ponds by natural processes involving natural oxygenfrom air, bacterial digestive processes and algae with their photosynthetic process and own
metabolism.
The system has mainly three components.
1. Anaerobic pond
2. Facultative pond
3. Maturation pond
Facultative and maturation ponds can be multiple. The ponds are generally in series. There may be
parallel serial systems.
These ponds are not constructed ponds. These are excavated in soil and the sides and bottom
are densely compacted so that the sides do not collapse. The shape is normally rectangular. Because
of the compaction, water does not permeate in the soil readily. When this system is used for sullage
or grey water, the required hydraulic retention time is less. In subsequent description, HRT suitable
for sullage or grey water has been mentioned.
a. Anaerobic pond
The first pond is an anaerobic pond, named thus, because in this pond, anaerobic digestion
takes place.
This pond has an effective depth of 8-10 feet and has a hydraulic retention time of 1-2 days.
If soil is very collapsible, a brick lining or stone pitching may be used for this pond.
The grey water flows into this pond as a first stage. The solids from grey water settle down in
this pond and gradually get anaerobically digested.
b. Facultative pond
The settled water from anaerobic pond is led through anaerobic pond outflow pipe system to
the facultative pond. It is called facultative because in this pond, bottom layer undergoes anaerobic
digestion while middle and upper portions have aerobic process in progress. In these ponds, thedigestive process is a result of three mechanisms.
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a. Aeration from air through the surface area
b. Pond bacteria utilize organic matter in the grey matter for their own metabolism.
c. Oxidation due to oxygen liberated from photosynthetic activity of algae due to incident sunlight.
Algae grow due to availability of plant nutrients from bacterial metabolism.
This pond has a depth of 4-5 feet and a hydraulic retention period of 3-5 days. Accordingly,length and width will have to be planned. Length should be thrice the width. If the shape of land is a
constraint, the length may be atleast twice the width. As stated earlier, the bottom and the sides
should be densely compacted. The sides should be sloping towards the bottom.
c. Maturation pond
The partially stabilized water from facultative pond is led through outflow pipe system to the
maturation pond.
In maturation pond, aerobic action takes place and BOD is highly reduced. Also, destructionof pathogens takes place in this pond.
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The dimensions of maturation pond are similar to those of facultative pond. The depth is 4-5
feet and HRT is 3-5 days. The length of the pond is thrice the width.
The outflowing water from maturation pond is safe to handle, has low BOD and can be
profitably used for agriculture, horticulture, pisciculture etc.
d. The interconnections
The interconnections between the ponds may be constructed in brickwork and preferably
PVC pipes of 100 mm-150 mm diameter can be used.
The layout of the system can be arranged to suit the shape and dimensions of available land
area.
e. Suitability for villages
This system is probably the most suitable system for management of community grey water
from the village. The system is low cost, can be easily established by villages themselves, the
maintenance is minimum and easily manageable by PRIs ie. Graam panchayats etc. The rivers and
nullahs will remain pollution free if PRIs located on the banks establish such systems in their own
villages.
2. Integrated waste management systems
Systems like DOSIWAM, DEWATS etc are based on the concept of stabilization tank system
with multi chamber digestion cum oxidation tanks. In Dosiwam system, human nightsoil is also
treated whereby biogas is produced for use as an energy source.
V. To end
This is a brief review of appropriate liquid waste management technologies for rural areas. The
choice of technology will depend on the situation at each place. These technologies, if used
extensively in rural areas will help change the face of villages. It will be a march towards clean,
healthy and prosperous villages in India.
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