Developing human health-related chemical guidelines for reclaimed wastewater irrigation

We examined the methodology of developing globally applicable human health-related chemical guidelines of using wastewater for crop irrigation. Two approaches may be used to develop pollutant loading guidelines: (a) preventing pollutant accumulation in waste receiving soil and (b) maximizing soil's capacity to assimilate, attenuate, and detoxify harmful chemicals. Pollutant loading rates based on the first approach are in agreement with the fundamental principle of maintaining ecological balances in soil. But numerical limits usually are very stringent and it is difficult for communities to meet these requirements. Recommendations derived with the second approach represent the maximum permissible loadings beyond which pollutant levels in the soil may be harmful to the exposed population. A method employing the second approach was evaluated. Preliminary pollutant loading limits for land application of wastewater are derived by considering the food chain transfer of pollutants via intake of grain, vegetable, root/tuber, and fruit grown on wastewater-affected soils.