Treated Effluent Re-Use for Agriculture

Mark Richards

IrrigationThe artificial application of water to the land

or soil.Used to:

assist in the growing of agricultural crops, protecting plants against frost, suppressing weed growth in grain fields preventing soil consolidation.

maintenance of landscapes,Re-vegetation of disturbed soils in dry areas

SHOULD ALWAYS BE ASSESSED TOGETHER WITH DRAINAGE

Irrigation & Agriculture

Irrigated agriculture has driven much of the increase in global food production over recent decades.

While only 20% of the world's farmland is irrigated, it produces 40% of our food supply.

Highest yields obtained from irrigation are more than double the highest yields from rainfed agriculture (FAO report).

Benefits of IrrigationImproving crop quality - most noticeable for

vegetable crops.Effective management of crop water needs –

supply water as needed.Planned agricultureImproved economics of farming

Significantly increasing crop yields particularly on sandy soils which have low moisture-holding capacities.

Increasing opportunities for double cropping.

 Providing a means of liquid fertilizer application.Possible reduction in fertiliser use

Reduction in production cost

Irrigation NeedsIrrigated agriculture is dependent on an

adequate water supply of usable qualityQuality not normally paramount in Jamaica

Availability of adequate good supplyNo real need to meet standards

Impact of development on ground water and surface water causing concern

Need for global tradeReduced availability of water

Competition for water

WATER QUALITY-RELATED PROBLEMS IN IRRIGATED AGRICULTURE

SALINITY Salts in soil or water reduce water availability to the crop to such an

extent that yield is affected.WATER INFILTRATION RATE

Relatively high sodium or low calcium content of soil or water reduces the rate at which irrigation water enters soil to such an extent that sufficient water cannot be infiltrated to supply the crop adequately from one irrigation to the next.

SPECIFIC ION TOXICITY Certain ions (sodium, chloride, or boron) from soil or water accumulate

in a sensitive crop to concentrations high enough to cause crop damage and reduce yields.

MISCELLANEOUS Excessive nutrients reduce yield or quality; unsightly deposits on fruit or

foliage reduce marketability; excessive corrosion of equipment increases maintenance and repairs.

MICROBIAL CONTAMINATION air, soils and plants in the vicinity of the irrigation site

Concerns for Effluent Re-useIn quantitative terms, the volume of

wastewater available for re-use by irrigated agriculture is negligible when compared with the overall volume of water used for irrigation.

The potential impacts associated with water quality and agricultural re-use of wastewater are importanteconomically, environmentally and socially,

Sound planning needs far exceeds the relatively small quantities and areas involved

Global GAP Certification

Recommendationsmicrobial and biochemical properties will have

to be evaluated.values should then be compared with the

public health standards, consideration of the crop, soil and irrigation

system and consumption of the produceonly when the effluent meets these standards

should it be evaluated in terms of chemical criteria such as dissolved salts, relative sodium content and specific toxic ions

Irrigation InfrastructureIrrigation Schemes

Pump Stations

Wells Canals Pipes (km)

Rio Cobre 18 22 26 31.01St. Dorothy 8 7 28 -

Yallahs 3 3 - 15.21Mid-

Clarendon32 32 153 36.10

New Forest 2 4 - 26Hounslow 5 5 - 41.40Beacon/

Little Park3 3 - 27.83

Seven Rivers

- 1 - 2.96

Colbeck 1 1 - 8.60Braco 1 1 - 8.60Grand Total

73 79 207 194.24

Water Quality from Existing Sources

What Happens Elsewhere  California Israel South Africa FR GermanyOrchards and vineyards

Primary effluent; no spray irrigation

Secondary effluent

Tertiary effluent, chlorination, No spray irrigation

No spray irrigation in the vicinity

Fodder fibre crops and seed crops

Primary effluent; spray irrigation

Secondary effluent, use on edible vegetables not permitted

Tertiary effluent

Pretreatment with screening and settling tanks.

Crops for human consumption that will be processed to kill pathogens

For spray no more than 23 coliform organisms per 100 ml.

Vegetables for human consumption 1000 coliform organisms per 100 ml in 80% of samples)

Tertiary effluent

Irrigation up to 4 weeks before harvesting only

Crops for human consumption in a raw state

For surface irrigation, no more than 2.2 coliform organisms per 100 ml.

Not to be irrigated with renovated wastewater unless they consist of fruits that are peeled before eating

  Potatoes and cereals - irrigation through flowering stage only

Example from Israel

Further RecommendationCulture change initiative

Farmers are presently averse to the re-usePublic Consultations/Public Education CampaignDevelop capacity of treatment facility to maintain

constant effluent qualityLong-term monitoring data to substantiate

Contingencies for emergency managementDevelop nutrient management capacity to

manage soil impact of treated effluent.Full re-use of waste is recommended

Waste to energyFertilizer development

100% of Influent Reused