Using waste water for irrigation

In water-scarce developing regions, urban wastewater is used to irrigate agriculture

Some factors contributing to this phenomenon include water scarcity and reliability of waste water supplies.  Also, crops irrigated with wastewater= higher profits.

This is an informal, unplanned, and ungoverned practice.  Officials see wastewater irrigation as a burden to govern and regulate.

The WHO has established guidelines on the usage of waste water for irrigation in attempt to reduce risks to human health and the environment.  However, the stated guidelines for waste water treatment prior to use for irrigation may be too costly for developing countries (at a price of US$125 to prevent one case of infection).

  

Currently, in Pakistan, approximately 32500 ha of land is irrigated directly with wastewater from cities. Crops irrigated with wastewater are mostly vegetables because they can fetch high prices in nearby urban markets (farmers using wastewater irrigation earned approximately $300 more per year than those using freshwater), and also because wastewater is a reliable supply than treated freshwater.

In some cases, wastewater is auctioned by the municipal council to the highest bidder, often a group of wealthier farmers who rent out their fields to poor landless farmers.  Under these conditions, wastewater irrigation is considered a win-win situation for both the authorities, who want to dispose of the wastewater, and the farmers, who get a reliable supply of water with a high nutrient content.

In Vietnam, irrigation with wastewater is a centuries old tradition.  Natural ponds collect wastewater and drainage from cities and discharge wastewater to canal systems. The ponds provide some level of natural treatment process for untreated sewage.  When the supply of irrigation water  is insufficient, city pumps discharge waste water to irrigation canals. Some farmers also use wastewater irrigation (at the tail end of sewage systems) where irrigation infrastructure is inadequate.

To mitigate health risks associated with wastewater irrigation, sprinkler use should be minimized because sprinklers have the highest capacity to spread illnesses.  Instead, the "bubbler, drip, or trickle methods" (localized methods that minimize possible area of contamination) should be used.  Protective clothing should also be worn.  If sprinklers are used, a buffer zone between farms and more urban areas should be set up.

-SEE CASE STUDIES ON NAIROBI, KENYA AND KUMASI, GHANA

citation:

Scott, Christopher, Faruqui, Naser I. and Liqa Raschid, eds. WASTEWATER USE IN IRRIGATED AGRICULTURE Confronting the Livelihood and Environmental Realities. IDRC, 2004. Accessed November 7 2010. http://www.idrc.ca/openebooks/112-4/