Industrial pollution-

Water pollution occure due to the presence of dissolved inorganic materials, organic materials like proteins ,fats , carbohydrates and physical factors like turbidity, colour, temperature of effluent, radioactivity etc.
Organic pollution due to presence of higher molecular weight compounds like sugars, oils, fats and proteins are obtained from distillery, canning like sugar and other food-processing industries. Some wastes from pharmaceutical and petroleum industries contain phenols which are toxic to fishes.
Turbidity of waste water is caused by the presence of colloidal matter which does not sel=ttle readily. This consist of fine clay particles, milk wastes, seage. Synthetic detergents, effluents from industries like paper-pulp, dye-stuff, tanning and textile industries add colour to the effluent.

Purification of water-
Impure water may be purified by one of the following method-
A) Natural 1) Pounding or storage
2) Oxidation and settlement.
B) Artificial 1) Physical
a) Distillation
b) Boiling
2) chemical
a) Precipitation
b) Disinfection
3) Filteration
a) slow and filteration
b) Rapid mechanical filteration
c) domestic filteration

Natural method of storing water helps in settling down of suspended particles. Use of a co-agulant like Aluminium sulphate in the contration of 13-50mg/lit. is suggested. Most of the settles down in the process. Oxidation with potassium Permaganate at a concentration of 5 parts per million are advisable.
Artificial method of distillation is used in chemical laboratories. Boiling removes solid material like chalk, obnoxious gases, organic matter and microbes. It is adapted as a precautionary measure in the presence of an epidemic of water-borne diseases. Use of filteration removes suspendes matter, the ova, cysts spores and bacteria. Slow sand filters use layer of bricks, broken stones, pebbles coarse and fine sand. The process of filtetarion is slow. It may take about 3 days for new bed of filters to be active. Rapid mechanical filters may be of pressure or gravity type. They are quick and filter about 450-600lit/24