(2) Water pollution:

Water pollution could be in the form of any change in the physical, chemical and biological properties of water which has a harmful effect on living things. It could take place in various water sources, like ponds, lakes, rivers, seas and oceans.
The factors that cause water pollution are as follows:

1. Industrial Waste Effluents:

Many of the chemical related and manufacturing industries like leather tanneries, fertilizers, oil refineries, petrochemical, textile, paper pulp, rubber products and agrochemicals are always generating by-products and waste effluents along with their desired products. The waste product may be in the form of waste heat, smoke, solid or waste water effluents. These may contain organic chemicals including highly toxic synthetic organic compounds and heavy metals i.e. Pb, Cd, Cr, Hg, As, Sb etc, oils, greases, mineral acids. These may result in contamination of both surface and ground water. Unfortunately, many industries release their waste products directly into rivers or let them leak into the groundwater and increasing water pollution. These chemicals are poisonous or toxic to plants, animals and people.

2. Pesticides:

Pesticides are organic and inorganic chemicals originally invented and used effectively for controlling undesirable insects and forms of life such as bacteria, pests, and foraging insects. Their effectiveness, however, has caused considerable pollution. The persistent or hard pesticides, which are relatively inert and non-degradable by chemical or biologic activity, are also bio-accumulative; that is why they are retained within the body of the consuming organism. The drainage water from the agricultural land (where pesticides are being used) mostly contains pesticides and pollutes water system not only at surface level but also at ground level due to leaching of pesticide.

3. Insecticides:

Insecticides are chemicals that are sprayed onto crops to kill the insects that eat crops. One of the more poisonous insecticides are DDT and organo-phosphates. Some specialists believe that these insecticides have caused even greater environmental damage and that they are more toxic. Insecticides are easily washed by the excess water and rain into streams and groundwater where they poison fish and domestic animals and also pollute food chain.

4. Fungicides:

Copper and mercury are two heavy metals, which are found in fungicides. Fungicides are also sprayed on crops and easily washed into rivers. These heavy metals are toxic to biological life including the people who may have to drink from the polluted water bodies.

5. Heavy Metals:

Heavy metals such as nickel, molybdenum, zinc, cadmium and lead are mined and processed by the mining and ore-smelting industries. These metals are easily washed into streams and groundwater and increase pollution. The crops that have been irrigated with polluted water can also be dangerous.
In the past, toxic waste products were dumped into the rivers or into landfill sites close to where people lived causing health problems and even death. Today all South Africans have a constitutional right to a clean and safe environment. Make sure that you remain informed and observant so that you can prevent toxic chemicals from being used in your environment. If you suspect water pollution in your area then contact your local council.

6. Oil Spills and transport:

Petroleum products are used as fuel, lubricants, for manufacturing petrochemicals, plastics, electrical appliances, synthetic rubbers and detergents. Sea water gets polluted by accidental oil spills and leakage from cargo oil tankers in sea, tanker trucks, pipelines leakage during offshore exploration and leakage of underground storage tanks. The spilled oil also damages marine life often causing their death.

7. Chlorine and Detergents:

Paper and pulp mills and textile factories are amongst the worst water polluters. Paper and pulp mills use up large amounts of water and produce a lot of polluted wastewater. The wastewater contains strong chemicals such as chlorine, which is used to make paper white and soft. Textile factories also release strong chemicals like caustic soda, acids, dyes and detergents into water.

8. Detergents:

Detergents are excessively used in industries and household as cleaning agents. The amount of disposed detergents in waste water is increasing day by day. This waste water when discharged in rivers or sea greatly affects aquatic life. The detergent contents of waste water mobilize the bound toxic ions of heavy metals like Pb, Cd and Hg from sedimentary rock into water.

9. Fertilisers and Sewage:

Some chemicals like fertilisers are made up of substances that do occur naturally in the environment, but only in small amounts. When too much fertiliser is washed from farmlands into a river then that water will also become polluted. Human sewage or cattle excrement that is untreated also causes water pollution in the same way as fertilisers do.