Types of Water Pollution

The main types of water pollutants include biological agents, chemical agents and physical agents.

Biological Agents: 

These include bacteria, parasitic fungi and protozoa. The main sources include human sewage, animal and plant wastes, decaying organic matter, industrial wastes (oil refineries, oil spills, oil pollutants, paper mills, food processing units, etc.) and natural land and urban run off and waste water discharges from slaughter houses. Some of the contributory factors are over population, unplanned industrial and human settlements and lack of civic amenities. The oxygen requiring bacteria feed on the biological wastes and this results in depletion of oxygen in the water bodies. In the absence of oxygen, life is destroyed. The water acquires foul odour.

Chemical Agents: 

These can be inorganic chemicals and minerals, organic chemicals and radioactive substances. The inorganic chemical agents include acids, salts (nitrates, phosphates etc.), metals like lead and mercury.

The main sources include natural run off from land, industrial wastes, leaded gasoline, lead smelting, agricultural chemicals run off from agricultural lands, mining, oil fields, food processing units, etc. In water bodies, the above pollutants are toxic to various forms of life and human beings and can cause genetic defects. The water is rendered unfit for human consumption (domestic, agricultural and industrial use). It is responsible for eutrophication.

The organic chemicals include agro-chemicals (pesticides, herbicides etc), detergents, chlorine containing compounds, oil, grease and plastics. The main source include agriculture, forestry, pest control industries, domestic and industrial wastes, paper industry, bleaching processes etc. Such polluted water is toxic to aquatic life and other organisms that are dependent of such water bodies. It may cause eutrophication of water bodies.

The radioactive substances are released into aquatic systems as a result of nuclear wastes from research laboratories and hospitals. These are also released by processing of uranium ores and nuclear plants. The radioactive substances enter the food chain and are responsible for birth and genetic defects. They are causative agents for cancer

Physical agents: 

These include suspended solids, particulates and heat. The main sources are soil erosion, run off from agriculture, mining and power Suspended organic and mineral solids absorb toxic substances like heavy metals and pass them through food chain. Aquatic animals face problems in breathing through gills in such waters. Thermal pollution occurs when hot water enters the water body. Increase in temperature lowers the solubility of oxygen in water thereby affecting aquatic life.