Wastewater, if recycled and reused with care, forms a lucrative source of water for irrigation due to its continuous and assured supply and high nutritional value.

Wastewater, refers to the municipal wastewater that contains a broad spectrum of contaminants resulting from the mixing of wastewater from homes, businesses, industrial areas and oftenstorm drains, especially in older sewer systems. Sewage, the subset of wastewater that is contaminated withfaecesorurine, but is often used to mean any wastewater, is  disposed of, usually via apipeor sewer (sanitary or combined), sometimes in acesspool emptier.Municipal wastewater is usually treated in a combined, sanitary, effluent or septic  tank. Septic systems treat sewage on-site and are used in rural settings.

Around 90% of urban wastewater produced globally, especially in low-income countries, remains untreated, since the ‘sewerage system’, the physical infrastructure, including pipes,pumps, screens, and channels etc. used to convey sewage from its origin to the point of eventual treatment or disposal is very costly. Sewage Treatment Plants are notoriously costly, require large amount of energy, and are difficult to maintain. Most often the effluent from the STPs does not measure up to the desired standard of treatment. As a result, large amount of urban sewage is directly disposed of into water bodies adjacent to the urban settlements, polluting downstream water sources.

Agriculture in the peri-urban areas has to compete for increasingly scarcewater resourceswith industry and municipal users and there is often no alternative for farmers but to usewaste water for irrigating their crops.Waste water, with continuous and assured supply and with high nutrients for plants, despite its health hazards, is attractive to farmers. Increasingly,agricultureis using untreated wastewater for irrigation and it needs to be encouraged as it provides eco-service by preventing pollution of nearby water bodies, albeit with caution as it can contain a mixture of chemical and biological pollutants with adverse impact on humans, plants and soil. To encourage safe use of wastewater in agriculture, theWorld Health Organization advocates a ‘multiple-barrier’ approach to wastewater use.Farmers are encouraged to adopt various risk-reducing behaviours such asapplying water carefully,ceasing irrigation a few days before harvesting, cleaning vegetables with disinfectant or allowing faecal sludge used in farming to dry before being used as a human manure.

In many developed countries, wastewater is fully treated before being used for irrigating parks, gardens and golf courses. In countries like Singapore and Israel, through high-tech methods, each drop of water is recycled many times before it reaches sea.