The addition of foreign matters in water, such as micro-organisms, industrial and other waste products, harmful chemical substances etc. is known as water pollution. Water resources are being polluted due to mix up of industrial wastage and drainage with drinking water pipes, which is responsible for so many water- borne diseases like diarrhea, typhoid etc. Rivers in urban areas are being polluted due to negligence.

Sources of water pollution:

 1. Industrial waste: Water is discharged from after having been used in production process. This wastewater may contain acids, alkalis, salts, poisons, oils and in some cases harmful bacteria.

2.Mining and agricultural wastes: Mines, specially gold and coalmines, are responsible for large qualities of acid water. Agricultural pesticides, fertilizers , and herbicides may wash into rivers and stagnant water bodies.

3.Sewage disposal and domestic wastes: Sewage as well as domestic and farm wastes were often allowed to pollute rivers and dams.

Effects of water pollution:

1. Water borne diseases like typhoid, dysentery, diarrhoea.

2. Drinking water containing salts of nitric acid(nitrates) methemoglobinemia (also known as blue baby syndrome). 

3. Water polluted by some of the inorganic substances such as mercury, lead, arsenic etc are very much harmful to health.

4. Eutrophication decreases dissolved oxygen in water hence disturbs aquatic ecosystem.

Control of water pollution:

1. Renovating the existing sewer lines and connecting them to central sewer line by branch and trunk lines.

2. All domestic sewage should be centrally collected. 

3. Industries may be forced to treat the effluents to a requisite quality standard and to be connected to a main sewer line.

4. Use of pesticides and insecticides should be discouraged.