摘要
Abstract:In the recent past,trace levels of many contaminants were reported in drinking water.Substances that are resistant to bacterial degradation will flow along with treated effluent and will end up in inland surface waters from which raw water is extracted for public water supply systems.In certain extreme situations,presence of excessive concentrations of these contaminants can inhibit bacterial degradation of biological wastewater treatment processes.Therefore,there is a natural tendency for build-up of these contaminants in water sources.The emerging contaminants found in drinking water are heavy metals and hazardous substances that flow along with industrial effluent,hospital effluent and agricultural runoff.In order to remove these substances that are resistant to biological wastewater treatment,it is recommended to separate them in concentrated form by a separate collection system without allowing to mix with other wastewater streams.For wastewater other than domestic nature containing heavy metals,residual dies etc.and hazardous wastewater generated from hospitals such as radioactive iodine treatment for cancer patients,chemicals used for X-ray processing,amalgam used by dentists to fill up cavities,antibiotics,laboratory chemicals such as salicylic acid,benzoic acid,ethidium bromide(used for molecular biology research),xylene,formalin for preserving biological specimens,etc.,must be separated in concentrated form in a separate collection system without mixing with wastewater of domestic nature and disposed after treatment as hazardous wastewater.As per the“Policy on Siting of High Polluting Industries”,it is not possible to locate industries that are categorized as Type“A”high polluting industries upstream of intakes that extract raw water to produce potable water supply as it is very difficult to remove these substances by conventional water treatment techniques.
