(a) Activities of man that pollute water bodies are:
(1) dumping of household refuse or organic wastes into water bodies
(ii) oil spillage from drilling or tankers
(iii) thermal pollution, hot water from industrial plants and atomic reactors
(iv) dumping of agro chemicals, e.g. fertilizers, pesticides, fungicides etc
(v) dumping of dye from textile factories into water
(vi) pouring detergents from homes and factories into water bodies
(vii) pouring tannins from leather factories into water bodies
(viii) radiations or radioactive fall-outs from nuclear plants washed into water bodies
(ix) untreated sewage dumped into water bodies
(x) use of dynamites/explosives for fishing
(xi) use of chemicals (Gamalin/DDT) in fishing.
(b) Measures for preventing pollution of water bodies are:
(1)Treatment of raw sewage before discharging into water and prohibition of disposal of human waste into water bodies
(2)Refuse must be burnt or buried and must not be deposited into water bodies
(3)Recycling of industrial waste before discharging them into water.
(4) Wastes should be discharged in controlled amounts.
(5) Cooling of water from industrial plants before discharging
(6) Proper sewage treatment
(7) Using biodegradable detergents in controlled amounts
(8) Limiting the use of pesticides and fertilizers
(9) Spraying oil with detergents to spread it or cover oil with chalk powder to cause it to sink and speed up bacteria decomposition/efficient method of preventing oil spillage
(10) Proper education of farmers on correct usage of fertilizers to limit run-off into water bodies
(11) Enactment/enforcement of laws to prevent the use of explosives and chemicals in fishing. The methods of purifying water are: boiling, addition of chemicals, e.g. alum, and chlorination; filtering; distillation; sedimentation and boiling; sterilization, e.g. by using u. v. light