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Sludgeless Effluent Treatment
Sludgeless Effluent Treatment
The effluents released by certain industries have created serious pollution of the water table in many areas. In collaboration with the local textile and leather industries, AuroZon of Pondicherry has developed a treatment applicable to most industries, based on biological digestion and ozone oxidation only. The conventional treatment to remove the colour and COD from heavily polluted effluents makes use of large quantities of hazardous chemicals such as lime and ferro sulphate. The entire mass of these chemicals comes out of the ETP as toxic sludges, which are dumped on landfills or accumulated in temporary sheds. But these sludges are themselves classified as hazardous. The process now offered consists in fulfilling the oxygen demand first by a good aerobic treatment (eventually preceded by an anaerobic stage if place is available for one more tank) followed by radical oxidation of the effluent obtained by injecting high concentration ozone gas in oxygen at 8% weight by weight. The sequence is completed by an adsorption stage by passing ozone treated effluent through granulated activated carbon. Such treatment removes entirely the most difficult dyes and reduces the COD to very low levels. These steps are eventually followed by a polishing phase using one more light injection of ozone known as ‘post-ozonation’. The process does not generate any sludge and hence the sludge beds and sludge sheds are done with. The small quantity of sludge produced by the residues from the treated pollution itself (and not by the residues from the added chemicals) is mostly organic and can be used for making compost or generating energy. The off-gas is also utilized and re-injected to accelerate the process. The treated effluent is easy to nanofilter and/or treats through RO so that most of the water can be reused. The life of the RO membranes is prolonged and the frequency of back wash is reduced. The replacement of the membranes is greatly postponed which decreases the cost of the RO filtration. The process makes use of low-cost/high-reliability generators of ozone designed and manufactured by Aurozon. Both the capital cost of the ETP and its running cost are lower than for the conventional treatment.