What are the preventive measures to control water pollution?
New techniques that need no water is highly beneficial. Some of the wet processes is replaced by the dry processes. For example, metal pickling once carried out by acids is replaced by sand blasting in which no liquid effluent is generated.
To minimize the volume of effluents, the waste water that is less polluted may be used in rinsing. For instance, in the mercerizing of yarn, the final rinse water containing little alkali is used for the first and second rinsing of yarn containing excess alkali.
Concentrated wastes, low in volume, are mingled with diluted waste for treatment or disposal. It can be segregated from other streams of diluted wastes, for reduction in pollution load and the diluted wastes after minor treatment is utilised for irrigation. This method is used for treating tannery effluents.
Small industries cannot afford treatment plants as they frequently discharge their effluents, near agricultural lands and on roads. It can be avoided by setting up a common effluent treatment plant where industries are located.
Waste can be converted into wealth. For instance, in our country distilleries can set up bio-gas plants which are fed by their effluents resulting in reduction in fuel costs and decrease in effluent's strength.
The sludge obtained is a problem. The sludge from pulp and paper industry may be used for manufacturing boards used in packing or in preparation of artificial wooden panels while those from the electroplating industry may form water-proofing compounds.
Recovery of chemicals and metals is practiced in most industries. The reclaimed waste water can be reused for industrial processes such as boiler, feeding, cooling, which will help cut down the fresh water needs. And paper mills, sugar industries and distilleries that let out more effluents can be used for irrigation or as fertilizers after proper treatment, without affecting ground water.