Urban wastewater : a valuable resource for agriculture : a case study from Haroonabad, Pakistan

Untreated urban wastewater is generally considered unacceptable for direct use because of potential health risks. However, in many parts of the world, poor farmers in peri-urban areas use untreated wastewater. This practice is likely to continue in the foreseeable future due to the high investment cost associated with the installation of treatment facilities.

In order to systematically document the advantages and disadvantages of using untreated urban wastewater, a case study was undertaken in Haroonabad, a small town in the southern Punjab in Pakistan. Information on costs and benefits associated with wastewater use was obtained by monitoring a group of 20 wastewater farmers and a group of 20 non-wastewater farmers over a one-year period. Water and nutrient applications and the quality of groundwater and soil were investigated in nine fields, of which some were irrigated with wastewater and others with regular canal water. To assess the human health impacts, a comparison was done between a settlement where wastewater irrigation was practiced and one where regular canal water was used.

The greatest benefit for farmers using wastewater was the reliable water supply, which allowed them to grow high-value vegetable crops. However, water and nutrient applications to wastewater-irrigated fields were excessive in relation to the recommended values, with improved distribution of wastewater, more farmers could benefit from the water and the nutrients it contains.

The study concludes, that whilst health risks (heavy metal accumulation and hookworm) should be identified, socioeconomic and environmental benefits should be maintained under the prevailing social and economic conditions.