6. Wastewater Treatment

Water is a universal solvent and a vital constituent of living organisms. It recirculates in the environment through the hydrologic cycle which can be hampered due to human activities in terms of pollution. Polluted water, known as wastewater or effluent, should not be drained without treatment, as it constitutes a serious threat to living beings. Parameters like biochemical oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), etc. are used to determine water quality. Therefore, wastewater treatment methods are targeted to get these parameters at optimum level. Such processes are either physico-chemical or biotechnological in nature and may be categorised as preliminary, primary, secondary and tertiary treatments. All of these must be followed by disinfection to obtain potable water. Major objectives of preliminary and primary treatment include removal of coarse and fine particle by screening, filtration, sedimentation, equalisation and flotation. Secondary treatment consists of biological treatment, i.e. aerobic, anaerobic and specialised reactors. Tertiary treatment entails chemical processes to purify wastewater. In the future, as the world’s population continues to grow, such research priorities will become increasingly paramount. At present, a change in research priorities can be observed, and new technologies that meet the requirements of sustainable development and multidisciplinary approach are being applied. Therefore, modified methods must be developed to be used in systemic combination to fulfil the demand of potable and reusable water.