Filter technology: integrated wastewater irrigation and treatment, a way of water scarcity alleviation, pollution elimination and health risk prevention

The use of urban wastewater in agriculture is a widely established practice for alleviating water scarcity situations and reducing or even eliminating the purchase of chemical fertilizers. However, unregulated irrigation with untreated wastewater poses serious public health risks, as sewage is a major source of excreted pathogens that cause gastro-intestinal infections in human beings. Wastewater may also contain highly poisonous chemical toxins from industrial sources that may cause much more serious long-term health risks. Reuse after proper treatment is normally recommended as the main solution of preventing health risks. Unfortunately, because of the high cost of engineering plants, most cities in developing countries do not have sufficient wastewater treatment capacity, and the perspectives of the capacity increasing in these cities are bleak. Planned and regulated wastewater irrigation with crop limitations and proper irrigation methods (for example local irrigation) may to some extent, prevent health risks. But for a given territory, it is often impossible to limit the type of crops to be grown. This paper introduces the FILTER (Filtration and Irrigated cropping for Land Treatment and Effluent Re-use) technique, an improved land treatment technique developed at CSIRO, Australia and tested both in Australia and China. FILTER combines the use of nutrient-rich wastewater for intensive cropping with filtration through the soil to a subsurface drainage system. Therefore, FILTER has the capacity to handle high volumes of wastewater in a relatively small land area and during periods of low cropping activity or periods of high rainfall. In order to produce minimum-pollutant drainage water which meets general environmental criteria for re-use and discharge to surface water bodies, the wastewater application and subsurface drainage in the FILTER system needs to be managed to ensure adequate removal of pollutants, while maintaining required drainage flow rates. Trial results indicate that a well-managed FILTER technique can reduce pollutant levels in drainage waters below EPA limits, while maintaining crop yields and nutrient removal to potentially make it a sustainable system.