Reuse of Treated Sewage Water in the UAE Capital : Resource Management and Impact on Food Safety

Reuse of Treated Sewage Water in the UAE Capital : Resource Management and

Impact on Food SafetyMrs. Manal Al-Hashemi

Inorganic ChemistryAbu Dhabi Food Control Authority (ADFCA)

Abu Dhabi,UAE

THE UNITED ARAB EMIRATES , UAETHE UNITED ARAB EMIRATES , UAE

UAE Water ResourcesMAIN FEATURES:MAIN FEATURES:

Arid ClimateArid Climate

High summer TemperaturesHigh summer Temperatures

Limited Conventional Water ResourcesLimited Conventional Water Resources

Increasing Demand Increasing Demand (agriculture, pop. Growth, urbanization )(agriculture, pop. Growth, urbanization )

Heavy dependence on seawater desalinationHeavy dependence on seawater desalination

UAE Water Consumption

Third Highest Consumption WorldwideThird Highest Consumption Worldwide

83% Consumption by Agriculture 83% Consumption by Agriculture

Increasing demands of Agricultural expansionIncreasing demands of Agricultural expansion

341% increase in desalinated water Supply341% increase in desalinated water Supply(1993(1993--2003).2003).

Abu Dhabi Water ResourcesDistribution:Distribution:

Water Resources (Year 2003 Estimates)

78.5%

0.5%17%

4%

Treated Wastewater Desalinated WaterFresh Groundwater Brackish Groundwater

Deteriorating Ground Water Resources

Abu Dhabi Water Consumption

Abu Dhabi Water Consumption (2003)

15.5%1.5%

58.0%

18.0%7.0%

Domestic Industry / CommerceAgriculture ForestryAmenity

Abu Dhabi Waste Treatment

Al Al MafraqMafraq Wastewater Treatment WorksWastewater Treatment Works(MWTW):(MWTW):

Over 40% of UAE Production Over 40% of UAE Production

Over 75% of Abu Dhabi Emirate Production Over 75% of Abu Dhabi Emirate Production

Tertiary Treatment Tertiary Treatment (Activated Sludge, Chlorination, Sand Filtration)(Activated Sludge, Chlorination, Sand Filtration)

MWTW Influent QualityMEANMAXIMUM MINIMUMParameter

313527Temperature °C

207330120 BOD (mg/L)

245471122 COD (mg/L)

386318TSS (mg/L)

623760500Soluble Sulphide(mg/L)

350058002500Conductivity (µS/cm)

MWTW Treated Effluent Quality

Abu Dhabi Treated Wastewater characteristics

Low level of total suspended solids Low level of total suspended solids (High (High water consumption)water consumption)

High recovery rate of 94% at MWTW :High recovery rate of 94% at MWTW :

Average incoming flow : Average incoming flow : 407,315 m407,315 m33/day/dayAverage outgoing flow : Average outgoing flow : 383,076 m383,076 m33/day/day..

Reuse of Wastewater in Irrigation (Abu Dhabi Emirate)

Over 360,000 ha of cultivated land Over 360,000 ha of cultivated land (Agriculture, Forestry, Amenities).(Agriculture, Forestry, Amenities).

Cultivated Land consumes Cultivated Land consumes over 2700 (Mmover 2700 (Mm³³/yr)/yr)of irrigation water of irrigation water (mainly ground water)(mainly ground water)..

Wastewater only used for irrigation of aroundWastewater only used for irrigation of around4000 ha of amenities 4000 ha of amenities (parks, gardens, etc)(parks, gardens, etc) ininAbu Dhabi city and environs. Abu Dhabi city and environs.

Reuse of Wastewater in Irrigation (Abu Dhabi Emirate)

MWTW wastewater production: 139.8 MmMWTW wastewater production: 139.8 Mm33/yr/yr

No measurement of efficiency of wastewater reuseNo measurement of efficiency of wastewater reuse

- No measurement of exact Quantities Used or No measurement of exact Quantities Used or Efficiency of irrigation methods used Efficiency of irrigation methods used

Food Crops Irrigated with Treated Wastewater (Abu Dhabi)

Prohibition of wastewater irrigation for food Prohibition of wastewater irrigation for food crops is the common practice, despite high crops is the common practice, despite high effluent quality.effluent quality.

Roadside date palm trees distributed among Roadside date palm trees distributed among local amenities are the only food crops local amenities are the only food crops irrigated with treated wastewater irrigated with treated wastewater

Factors Discouraging Wastewater Reuse in Food Crop Production

Social FactorsSocial Factors

Food Safety and Health risk assessmentFood Safety and Health risk assessment

Lack of a clear water management policyLack of a clear water management policy

Factors Discouraging Wastewater Reuse in Food Crop Production

Social FactorsSocial Factors

Public awareness and acceptability of productsPublic awareness and acceptability of products

Misconceptions regarding risk involvedMisconceptions regarding risk involved

Ignorance regarding real but unknown risksIgnorance regarding real but unknown risks

Factors Discouraging Wastewater Reuse in Food Crop Production

Food Safety & Health Risk AssessmentFood Safety & Health Risk Assessment

Restricted & Unrestricted IrrigationRestricted & Unrestricted Irrigation

Risk of Eating Raw Vegetables Risk of Eating Raw Vegetables

Risk of Contact with Treated Irrigation WaterRisk of Contact with Treated Irrigation Water

Food Safety & Food Safety & Health Risk AssessmentHealth Risk Assessment

Unrestricted Irrigation:Unrestricted Irrigation: Irrigation of all food Irrigation of all food crops, crops, includingincluding vegetables and salad crops vegetables and salad crops eaten raw.eaten raw.

Health Concerns:Health Concerns:

Consumer SafetyConsumer SafetyField Staff SafetyField Staff Safety

Food Safety & Food Safety & Health Risk AssessmentHealth Risk Assessment

Restricted Irrigation:Restricted Irrigation: Irrigation of all crops Irrigation of all crops exceptexcept vegetables and salad crops eaten raw.vegetables and salad crops eaten raw.

Prime Health Concern:Prime Health Concern:

Field Staff SafetyField Staff Safety

Food Safety & Health Risk AssessmentFood Safety & Health Risk Assessment

Risk of Eating Raw VegetablesRisk of Eating Raw VegetablesTreated Wastewater:Treated Wastewater: For Quality within For Quality within 1000 1000 faecalfaecal coliforms/100 ml (WHO), coliforms/100 ml (WHO), Estimated Risk = 10Estimated Risk = 10--66 or or 0.0001%. *0.0001%. *

UnTreatedUnTreated WastewaterWastewater::

Estimated Risk = Estimated Risk = 5 5 –– 15 % 15 % ((FattalFattal et al., 2004)et al., 2004)

Abu Dhabi Abu Dhabi Treated Wastewater: Treated Wastewater: AverageAverage< 50 < 50 faecalfaecal coliforms/100 ml (Well below coliforms/100 ml (Well below international Safety Margin).international Safety Margin).

_____________________________________

* USEPA acceptable risk level = 0.01% (10-4)

Consumption of Food in Contact with Treated Wastewater (Abu Dhabi)

: Imported Vegetables irrigated Imported Vegetables irrigated with water of unknown Qualitywith water of unknown Quality

Risk of Contact with Treated Wastewater

No Risk for Abu Dhabi’s Wastewater !!

Food Safety & Health Risk AssessmentFood Safety & Health Risk AssessmentRisk of Contact with Treated Irrigation WaterRisk of Contact with Treated Irrigation Water

Increased Infection Risk:Increased Infection Risk: For contact with For contact with sprinkler water containing: sprinkler water containing:

101066 faecalfaecal coliforms/100 mlcoliforms/100 ml

No Increased Infection Risk: No Increased Infection Risk: For contact withFor contact withsprinkler water containing:sprinkler water containing:

101033 -- 101044 faecalfaecal coliforms/100 ml coliforms/100 ml (WHO limit to 10 times the limit)(WHO limit to 10 times the limit) [Blumenthal et al., 2002][Blumenthal et al., 2002]

Abu Dhabi Abu Dhabi Treated Wastewater: Treated Wastewater: AverageAverage< 50 < 50 faecalfaecal coliforms/100 ml (Well below coliforms/100 ml (Well below international Safety Margin).international Safety Margin).

Factors Discouraging Wastewater Reuse in Food Crop Production

Lack of a Clear Water Management PolicyLack of a Clear Water Management Policy

Lack of integrated conservationist resource Lack of integrated conservationist resource management policy.management policy.

Availability of expensive nonAvailability of expensive non--conventional conventional sources.sources.

Water management policy oriented towards Water management policy oriented towards increasing supply rather than controlling increasing supply rather than controlling demand.demand.

Advantages of Wastewater Advantages of Wastewater Reuse in Food Crop IrrigationReuse in Food Crop Irrigation

Contribution to the conservation of overContribution to the conservation of over--abstracted underground resources. abstracted underground resources.

Environment Protection by reducing Environment Protection by reducing pollution from desalination plants. pollution from desalination plants.

Environment Protection by providing Environment Protection by providing substitute to chemical fertilizers. substitute to chemical fertilizers.

Advantages of Wastewater Advantages of Wastewater Reuse in Food Crop IrrigationReuse in Food Crop Irrigation

Soil enrichment with nutrients (N, P, K) :Soil enrichment with nutrients (N, P, K) :Increased ProductionIncreased ProductionSaving Fertilizer Cost Saving Fertilizer Cost

Economic benefit of providing a cheaper Economic benefit of providing a cheaper alternative to irrigation with expensive alternative to irrigation with expensive desalinated water. desalinated water.

Protection of agricultural soil by providing a Protection of agricultural soil by providing a substitute to irrigation with highly brackish substitute to irrigation with highly brackish or saline well water. or saline well water.

Conclusions & RecommendationsBased on existing data gathered over more than 20 years regarding the quality of Abu Dhabi treated wastewater (under tertiary treatment),it is safe to say that the reuse of wastewater in food crop irrigation is highly recommended and poses no real risk to food safety .

Conclusions & RecommendationsReuse of wastewater in food crop irrigation is highly recommended:

To protect conventional water resources;

To protect & improve the quality of agricultural soil through valuable nutrients that increase agricultural production;

To protect the environment by reducing pollution associated with other water sources.

Conclusions & Recommendations

To conduct research to assess the risk involved with the sizeable imports of raw-eaten fruits and vegetables of unknown history which may have been irrigated with poorly treated wastewater or even raw sewage.

Conclusions & Recommendations

Frequent monitoring of chemical and microbiological safety of imported food crops eaten raw with special emphasis on helminthes eggs and other parasites.

Conclusions & Recommendations

Food control authorities need to Food control authorities need to develop highly efficient develop highly efficient parasitological labs.parasitological labs.

Conclusions & Recommendations

Imposition of regulations compelling vegetable exporters to the UAE to provide certified documents indicating the type of irrigation water used and whether or not wastewater (treated or untreated) was used.

Conclusions & Recommendations

To Manage wastewater reuse within the framework of a comprehensive water resource management strategy.

Conclusions & Recommendations

Competent authorities need to monitor and measure the efficiency of irrigation with wastewater with a view to reduce water demand by improving the efficiency of irrigation networks ; adopting more efficient irrigation methods and maintaining seasonal water reservoirs at the sewage treatment plants.

Conclusions & Recommendations

Competent authorities need focus on managing water demand by re-planning the development of farmed areas in terms of quantity and quality and adopting plans to introduce low-water consumption plants.

Conclusions & Recommendations

Competent authorities must adopt means , such as sign posts, to alert the public using recreational amenities that the treated wastewater used for irrigation is not of potable quality.

Thanks

Date Palm irrigated with Treated Sewage Water Date Palm irrigated with Treated Sewage Water in Abu Dhabiin Abu Dhabi