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WASTEWATER REUSE IN IRRIGATION
(reclaimed water reuse)
A proposal from the academy or a marked reality ?
Wastewater reuse in irrigation is becoming a popular practice.
Agricultural irrigation with treated wastewater (also called "reclaimed water") is becoming a common and
rapidly increasing practice in arid and semi-arid regions.
New wastewater reuse projects are reported almost every year from countries all over the world.
Why irrigation with reclaimed water is growing so fast.
Four main reasons are responsible for the fast growth of wastewater irrigation:
- Reclaimed water serves as an extra source of water available for the rural sector for irrigation. This source is especially important in
regions with limited water resources, where the increasing water demand by the urban sector (usually due to a combination of population growth and
increasing living standards) is replenished by reducing the water supply to the agricultural sector. The supply of treated wastewater is quantitatively
reliable for the farmers, since it depends neither on precipitation nor on the water balance of the whole region.
- Irrigation adds significant polishing treatment to the effluents via break-down of xenobiotic compounds in the soil, evaporation of
volatile compounds, pathogens die-off, biological degradation of remaining organic matter, and other processes.
- Surprisingly, disposal of the treated effluents via irrigation may be the cheapest disposal alternative (for both construction
and operational costs) when compared with disposal via discharge to rivers or lakes.
- Disposal of the treated effluents via irrigation may also be the alternative with the minimal impact on the environment.
Potential transmission of waterborne diseases ?
There is a serious concern about the potential transmission of diseases through wastewater irrigation, mainly in those countries without experience on this practice.
The concern is based on serious considerations, but the experience gained by those countries where wastewater reuse in irrigation is a common practice allowed the
development of a series of criteria to avoid this problem.
These criteria include:
- Guidelines on the quality of the effluents and the required treatment system.
- Limitations on the types of crops that can be irrigated with effluents of different qualities.
- Limitations on the technology used for irrigation (flood, sprinklers, drip irrigation, etc.).
- Better sewage treatment, storage and disinfection technologies developed during the last 10 years.
There are two main “schools” regarding the quality standards or guidelines for wastewater reuse in irrigation
–the so called the “WHO-World Bank” and the “California” schools- which have different and somewhat contradictory recommendations.
But wastewater irrigation practice continues to increase around the world in spite of these contradictions.
Most wastewater irrigation projects are not dedicated to irrigation of vegetables eaten raw.
The most conspicuous differences between the two above quoted “schools” are found in the wastewater quality required for the irrigation of
vegetables eaten raw (e.g. parsley and lettuce) or that have a direct contact between the vegetable and the water (e.g., potatoes).
It must be noted that MOST of the WW irrigation projects around the world are not dedicated to the irrigation of vegetables eaten raw, or to vegetables
at all. Hundreds of successful wastewater reuse projects perform irrigation of corn, olive trees, wine grapes, cotton, tomatoes dedicated to canned products,
flowers, golf courses, etc.
Wastewater irrigation in Israel.
Israel started to perform massive wastewater reuse in irrigation in the seventies, for cotton production.
Many lessons were learned since those years, and all kind of crops are presently irrigated with reclaimed
water. Today, more than 70 % of Israel sewage is reused in agriculture irrigation.
There are about 200 wastewater storage open reservoirs in the country, and many new projects are at an
advanced step of planning and
construction. Treated wastewater is seen as an integral part of the water resources of the country.
With 30 years experience on the massive use of wastewater for irrigation and long-term intensive R&D efforts to integrate reclaimed water
to the water resources of the country, Israel is today one of the leading countries in the world regarding
wastewater reuse.
Our contribution to Wastewater Reuse.
We have been involved in many of the main reuse projects in Israel and numerous reuse projects abroad. We have also contributed to the international
efforts to promote water reuse in the Mediterranean Region and around the world, through our active participation in the Specialists Group on Water Reuse of the IWA-International Water Association.
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