Water pollution is the contamination of water bodies, including lakes, rivers, oceans, aquifers, and groundwater.
It occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds, thereby compromising water quality.
Furthermore, Pollution is a condition disturbing the balance of the natural environment in such a way that its beneficial use is adversely affected.
Table of Contents
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Effects of Water Pollution
Here are the effects of water pollution:
- Water pollution decreases the value of water by deteriorating its fitness for various social and economic uses such as community water supply, recreation, and irrigation.
- The Determination of water quality may lead to an expensive water supply system, which involves complex treatment works.
- The Deposition of solids in water bodies hence reduces their capacities. The reduction of water bodies’ capacities may lead to a flooding disaster, especially in rivers and the disappearance of lakes.
- Toxicity to aquatic organisms. Typically, this occurs when water bodies are contaminated by industrial waste.
- Reduction/removal of dissolved oxygen (DO) from water bodies. This leads to the disappearance of organisms that rely on dissolved oxygen, such as fish.
- Luxuriant growth of plants in water bodies, especially lakes. Plants may become a big forest, and hence the disappearance of the water bodies.
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Water Management
Water management is a broad subject that needs special attention, as it involves many factors for consideration, such as:
- Thorough knowledge of the characteristics of aquifers and drainage (catchment) basins.
- Protection of water sources and their recharge and discharge areas.
- Optimum uses of fresh water.
- Conjunctive use of both ground, surface, and rainwater.
- Determination of the safe yield figure to avoid groundwater overdraft.
- Regular monitoring of water quality and quantity.
- Enactment of laws, by-laws or legislation for water sources protection and water utilisation control and regulation.
- Mass education on water management and its role to play in it.
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The Beneficial Uses of Water
The following are the beneficial uses of water:
Water supply, Recreation and aquatic life
Pollution causes undesirable changes and threatens the land, water, air, and outer space environment.
Man requires a clean and ecologically well-balanced environment, i.e., one that is beautiful, clean, healthy, scenic, and refreshing.
Water has such a strong tendency to dissolve other substances due to its polar molecular structure. Thus, pure water is never found in natural conditions in either surface waters or subsurface waters.
It always has something dissolved or suspended in it. The distinction between polluted and unpolluted water can be made depending on the following:
- the type and concentrations of impurities, and
- The intended use of water.
Also, the concentrations of the dissolved/ suspended substances can be compared with water Quality standards set for a particular use.
In general, water is considered polluted when it contains enough foreign material to render it unfit for a specific beneficial use, e.g., drinking, recreation, fish propagation, etc.
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Classification of Water Pollutants
- According to the nature of the pollutant origin, the following are the classifications of water pollutants:
- Point-source Pollutant: This is the one that reaches the water from a pipe, channel, or any other confined and localised source. E.g., waste water discharged from an outfall sewer/ drainage channel into a water body.
- Dispersed (diffuse or non-point) source pollutant: The source is abroad, unconfined, from which the pollutant enters a body of water. For example, surface runoff from agricultural areas carries silt, fertilisers, and animal wastes into streams, but enters not only at one particular point. Furthermore, acidic runoff from mining areas also affects stormwater drainage systems in urban areas.
- Background pollutants: These are derived from natural origins. They depend on the geological and topographical characteristics of the site, the type of vegetation cover, and climatic conditions.
Point source pollutants are easier to deal with than dispersed source pollutants. These pollutants from a point source may be collected and conveyed to a single point where they can be removed from the water in a treatment plant.
The point discharges from the treatment plants can easily be monitored by regulatory agencies (a discharge permit may be needed for point sources).
The most effective way to control the dispersed sources is to set appropriate regulations on land use.
2. Based primarily on either environmental or health (hazards) effects:
The following are water pollutants based on either environmental or health effects:
- pathogenic organisms
- oxygen-demanding substances
- plant nutrients
- toxic organics
- inorganic chemicals
- radioactive substances
- sediments
- heat
- uranium
- oil
- bacteria
- petroleum
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Sources of Water Pollution
1. Domestic Sewage:
Improper handling of domestic sewage after its production may lead to underground water pollution.
The effluent received at the end of the sewage treatment plant is of adequate standards. Sewage or partly treated sewage is being directly discharged into surface waters.
Sewage carries oxygen-demanding substances, i.e., organic waste, which exert BOD as they decompose by microbes.
The BOD changes the ecological balance in the water body by depleting dissolved oxygen content. Nitrogen and phosphorus (major plant nutrients) are in sewage as well as runoff from farms and suburban towns.
To decrease the amount of nitrogen and phosphorus in sewage, some forms of advanced sewage treatment must be applied.
2. Industrial Waste
This happened:
- If the wastes are discharged into water bodies without proper treatment.
- Waste disposed of by land treatment has a chance of polluting groundwater by leaching.
The Industry waste may carry many harmful substances, e.g, grease, oil, explosives, highly odorous substances, toxic organics, inorganic chemicals, and radioactive substances.
3. Stormwater (i.e, Surface Runoff)
This causes soil erosion and thus carries with it an amount of soil particles in suspension. Soil particles suspended in water interface with the penetration of sunlight.
This reduces the photosynthetic activity of aquatic plants and algae, disrupting the ecological balance of the stream.
The water velocity decreases, and the suspended particles settle out and get deposited as sediment at the bottom of the stream/ lake. These sedimentation deposits disrupt the reproductive cycles of fish and other life forms.
Land use activities, such as agriculture and construction, which temporarily remove natural vegetation and expose bare soils, are the main causes of severe erosion and sediment problems.
4. Heat
The amount of water withdrawn for cooling purposes in power plants exceeds the amount of water used for any other purpose.
The cooling water carries away waste heat as it passes through the condensers in the plant (steam in the condensers is converted back to water). The temperature may increase by up to 15 Degrees.
The discharge of warm water into a river is usually called thermal pollution. The warmer temperature decreases the solubility of oxygen and increases the rate of metabolism of fish (i.e, increasing the dissolved oxygen consumption).
Thermal pollution may be controlled by passing the heated water through a cooling pond or a cooling tower after it leaves the condenser.
The heat is dissipated into the air, and the water can then be either discharged to the river, pumped back to the plant or reused as cooling water.
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Types of Water Pollution
These types of water pollution may broadly be divided into the following three categories:
1. Physical Pollution
This occurs due to these factors: colour, taste, and odour, temperature, turbidity, suspended matter, radioactivity, or foam.
2. Chemical Pollution
This occurs due to the presence of the following:
- Inorganic chemicals: Acids, alcohols, toxic inorganic compounds, dissolved inorganic compounds, and suspended inorganic substances.
- Organic chemicals are due to the presence of fats, proteins, carbohydrates, and other organic substances. Organic chemicals are in two forms, suspended and dissolved.
3. Bacteriological Pollution
This occurs due to the presence of pathogenic microorganisms such as bacteria, protozoa, fungi, algae, viruses, and parasitic worms.
These organisms multiply excessively in water bodies, and they are infectious and harmful to public health.
The important sources are domestic and industrial sewage from certain trades. Solid excreta of human and decomposable organic matter of sewage give an excellent medium for the development of bacteria in water. It may lead to the outbreak of diseases.
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Pollution of Flowing Waters
Rivers and streams are flowing waters – i.e, surface waters in which the entire water body continually moves downhill in natural channels under the force of gravity.
These waters are shallower and narrower than impounded waters (lakes and reservoirs) and have a greater proportion of water exposed to land surfaces.
To a limited extent, streams/ rivers can assimilate biodegradable wastes. Thus, they can recover from the effects of pollution naturally without significant or permanent environmental damage.
This process is known as self-purification, and its capacity depends on:
- The strength and volume of pollutants and
- The stream discharge (flow rate).
Self-Purification Process
There are two basic stages of the waste assimilation process in a stream or river:
- Physical process of dilution and reaeration,
- biochemical process, in which microorganisms in the water use dissolved oxygen to metabolise organic pollutants and convert them into harmless substances.
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Pollution of Impounded Waters
The pollution of natural lakes or conservation reservoirs poses problems that are different from the problems caused by pollution of streams and rivers.
Water in the stream is constantly moving and providing flushing for incoming pollutants. But in lakes, the water is not moving very much at all and is detained for a relatively long time.
In some cases, pollutants discharged into a lake can remain there for many years. Lakes are also significantly affected by seasonal temperature changes.
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Pollution of Groundwaters
Groundwater is usually of excellent quality. This is due to natural filtration that occurs in layers of soil through which the water slowly passes.
The distance that pollutants can travel in the ground before being separated from the groundwater depends on:
- type of soil, i.e., fine sand, coarse gravel,
- The type of pollutants
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Last Thought on Water Pollution
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