Sources of Water Pollution

With the speedy growth of population, urbanization and industrialization environmental pollution has greatly increased. The main sources of water pollution arise from many activities. The sources of water pollution can be classified as natural and anthropogenic (human-made), and on basis of source identification.

a. Natural Sources:

• Surface runoff, seepage from groundwater and swamp drainage are the important natural sources of water pollution.
• Rain water is reported to be acidic in urban areas, due to the reaction between water droplets and atmospheric oxides of sulfur and nitrogen.
• Decaying bodies of animals and plants, decay of large quantities of organic matter in swamps or deep ponds leachates from animal excreta, solid waste landfill sites also introduce significant amounts of soluble organics and microorganisms which in turn pollute the adjacent groundwater.

b. Anthropogenic Sources:

Anthropological sources are the result of industrial, domestic, agricultural and mining activities of man.

• Domestic Sources- Municipal sewage that includes commercial buildings and institutions, wastewater from houses is discharged into the nearby canal, thus polluting the canal and also deteriorating the quality of groundwater.
• Agricultural Sources- Pollutants discharged into water courses due to agricultural activities include:  Agricultural run-off, Synthetic fertilizers, Soil and silt removed by erosion, herbicides and insecticides, plant residue.
• Industrial Sources- Industries such as pulp and paper mills, tanneries, sugar mills, oil refineries, distilleries, etc. produce a large quantity of wastewater which is discharged into natural waterways.
• Mining Sources- Mining operation also generates soluble toxic materials depending on the geological formation. Arsenic residues from gold mines, acid drainage from coal mines are some of the burning issues of environmental concern.

On the basis of Source Identification 

1. Point Sources

Involve discharges of wastes from identifiable points. Example: Stormwater runoff from combined storm and sanitary sewer lines, Sewage treatment plants (cannot remove all pollutants), Animal feedlots.

2. Non-point Sources

These sources are recognized as a major problem since the sources are widely spread out, difficult to identify and hard to control. These involve the diffuse discharge of wastes from atmospheric washout, land runoff, and source that are difficult to identify, measure the quantity and control. Example: Runoff sediment from natural and human-caused forest fires, logging and farming, construction, runoff of pesticides and chemical fertilizers.