Water Pollution

It is the introduction of harmful substances into the water.

Sources and Causes of water pollution

• Industrial effluents e.g. heavy metals, organic compounds, nitrogen, phosphorus, hot effluents
• Domestic waste and raw sewage
• Oil spills
• Agrochemicals
• Soil erosion
• Lead

Effects of water pollution

• Industrial effluents
• Contains heavy metals such as lead and mercury. These kill aquatic life and pollute domestic water.
• Contains wastes of organic compounds, nitrogen and phosphorus. May lead to eutrophication (massive growth of aquatic algae/water plants due to accumulation of nitrates and phosphates in the water body). Eutrophication leads to reduced oxygen thus cause the suffocation of organisms. It also leads to reduced light penetration into the water thus reduce photosynthesis.
• Hot effluents reduce dissolved gases in water and kill some organisms.
• Domestic waste and raw sewage
• Involves disposal of wastewater with detergents, garbage, faeces and nitrogenous wastes into water masses.
• It gives rise to disease epidemics such as cholera, amoebic dysentery and typhoid.
• The pollutants also kill aquatic life such as fish as there is a shortage of oxygen in the water.
• Oil spills

Oil spillage occurs in the oceans from oil tankers and offshore oil refineries.

• The oil layer reduces oxygen supply in the water, and this leads to suffocation and death of aquatic plants.
• The oil coats photosynthetic algae and kills them.
• The oil layer leads to reduced light penetration into the water which affects photosynthesis.
• Agricultural chemicals

Include fertilizers, pesticides and herbicides.

• They contain heavy metals like lead and mercury which are toxic.
• They reach water through seepage especially when it rains.
• They affect respiratory systems of aquatic organisms. Lead to death of organisms when they get to high concentrations.
• Nitrates and phosphates cause eutrophication in water bodies.
• Lead

Comes from pipes and tanks in domestic water supply systems.

• It affects the physiological functioning of body organs.
• It damages the nervous, resulting in mental problems.
• Soil erosion
• Causes siltation in water bodies, making water unfit for domestic use,
• It clogs respiratory surfaces of aquatic organism like gills in fish and stomata in plants, thus interfering with gaseous exchange.

Control of Water Pollution

• Treating sewage and industrial waste.
• Using biodegradable organic fertilizers.
• Replacing metal pipes with plastic pipes.
• Practicing good farming methods like contour farming to reduce soil erosion
• Establishing laws against oil spillage by tankers and imposing penalties.
• Educating the public on correct use of agricultural chemicals.