Integrated Wastewater Management

Wastewater or sewage originates from three sources: domestic wastewater from homes, industrial wastes, and agricultural wastes containing animal waste. Recognising the importance of clean, potable water, the Government passed the Water (Prevention and Control of Pollution) Act in 1974, which made treating wastewater in dedicated treatment plants mandatory. Treatment itself proceeds through three broad approaches. Physical methods handle wastewater containing insoluble substances or colloids through processes such as flotation, sedimentation, filtration, and centrifugal separation -- essentially separating solids from the liquid mechanically. Chemical methods work by generating insoluble solids or an insoluble gas from dissolved contaminants, by converting a non-biodegradable substance into a biologically degradable one, or by oxidising or reducing a contaminant into a non-objectionable substance. Biological methods rely on living organisms to break contaminants down: bioremediation of wastewater includes aerobic treatment (using oxidation ponds and aeration lagoons) and anaerobic treatment (using anaerobic bioreactors and anaerobic lagoons), while phytoremediation of wastewater uses plants and constructed ecosystems, including constructed wetlands, Root Zone Wastewater Treatment (RZWT), and Decentralized Waste Water Treatment Systems (DEWATS). Two real Tamil Nadu-region case studies illustrate phytoremediation in practice: Auroville, near Puducherry, has pioneered natural wastewater recycling using a DEWATS system, and similar plant-based treatment pl …