Water pollution is the pollution or contamination of natural water bodies like lakes, rivers, streams, oceans, and groundwater due to inflow or deposition of pollutants directly or indirectly into water systems. Water pollution very often caused by human activities.
Any modifications or change in the chemical, physical and biological properties of water that can cause any harmful consequences on living things and the environment is known as water pollution.
There are may types of water pollution depending on the sources the pollutants originate from. Types of water pollution are as follows:
Sewage water, waste water that contain high level of nutrients enter into water bodies. Nutrients in water encourage the growth of algae and weed in the water. This is known as eutrophication. This makes the water unfit for consumption and clog filters. Algal blooms in the water consume all the oxygen in the water, leading to suffocation for other water organisms.
Surface Water Pollution
Surface water includes rivers, lakes, oceans, streams, lagoons. Surface run-off substances that are hazardous dissolve and mix with water polluting the surface water. These run-off substances can be from any source like factories, domestic, sewage, agriculture etc.
Increase in the content of biodegradable matter in the water encourages the growth of microorganisms which end up using most of the oxygen. This results in oxygen depletion, killing aerobic organisms producing more of toxins like ammonia and sulphides.
Ground Water Pollution
Chemicals from fertilizers and pesticides applied to the soil are washed off and seep in the ground contaminating the composition of the ground water causing pollution.
Sometimes pollution is caused by microorganisms like bacteria and protozoa, this natural pollution can be lethal for fishes and other water life. Consumption of this water can lead to serious illness to humans.
Particulate matter of chemicals and other substances do not dissolve in water easily. These suspended particulate matters settle at the bottom of the water body harming the aquatic life at the floor of the water bodies.
Chemical Water Pollution
Most of the industrial let-off and chemical fertilizers used in farming end up in the water bodies. These materials are poisonous to most of the aquatic life, can make them infertile and eventually cause death. Water from these sources is obviously unfit for consumption.
Oil tankers and offshore petroleum refineries cause oil leakage polluting water. Oil spills can cause death of many aquatic organisms and also stick to the bodies and feather so seabirds which makes them unable to fly.
Domestic sewage is the waste water from households. It is also includes sanitary sewage, and it contains a variety of dissolved and suspended. Domestic sewage contains disease causing microbes and chemicals contained in washing powders affect the health of all life forms in water.
The practices followed in agriculture affect the groundwater quality. Intensive cultivation causes fertilizers and pesticides to seep into the groundwater; this process is known as leaching. Irrigation run-off from agricultural fields causes high nitrate content in ground water.
Untreated waste water from manufacturing industries contributes to water pollution.
Thermal Water Pollution
Thermal water pollution is the rise or fall in water temperatures. This changes in the temperature of water can be caused due to industries. Some industries use water as cooling agent, the heated water is let-off directly into the natural environment at a higher temperature. Cold water pollution happens when cold water is released into the water bodies. Aquatic organisms like fish are vulnerable to slight changes in the temperature. Heated water decreases oxygen in the water killing fish and other aquatic organisms. Cold water affects eggs and larvae, some invertebrates of the aquatic ecosystem.
Sources of water pollution, particularly ground water pollution are group under two categories based on the origin of the pollutant.
Point Source Pollution
Water pollution caused by point sources refers to the contaminants that enter the water body from a single, identifiable source like pipe or ditch. Point source pollutants can be discharges from sewage treatment plant, factories or a city storm drain.
Nonpoint Source Pollution
Pollution caused by nonpoint sources refers to the contamination that does not originate from a single source. Nonpoint source pollution is the cumulative effect of small contaminants gathered in large area. Leaching of nitrogen compounds from agricultural land, storm water runoff over an agricultural land or a forest are examples of nonpoint source pollution.
Major water pollutants are as follows:
- Sewage pollutants include domestic and hospital wastes, animal and human excreta etc. The sewage let off causes oxygen depletion, spread of diseases/epidemics.
Metals - Metals like mercury are let off into water bodies from industries. Heavy metals like mercury cause poisoning and affect health causing numbness of tongue, lips, limbs,deafness, blurred vision and mental disorders.
Lead - Industrial wastes also lead to Lead pollution. If lead enters the human body system in higher quantities it affects RBCs, bone, brain, liver, kidney and the nervous system. Severe lead poisoning can also lead to coma and death.
Cadmium - Source for cadmium pollution is industries, fertilizers. Cadmium gets deposited in visceral organs like liver, pancreas, kidney, intestinal mucosa etc. Cadmium poisoning causes vomiting, headache, bronchial pneumonia, kidney necrosis, etc.
Arsenic - Fertilizers are source for arsenic pollution. Arsenic poisoning causes renal failure and death. It also causes liver and kidney disorders, nervous disorders and muscular atrophy, etc.
Agrochemicals like DDT - It is a pesticide. Accumulation of these pesticides in bodies of fishes, birds, mammals and man affects nervous system, fertility and causes thinning of egg shells in birds.
Bacteria, Viruses and Parasites - These are sourced from human and animal excreta, they are infectious agents.
Plastics, Detergents, Oil and Gasoline
- They are a waste from industries, household and farms. They trigger organic pollution and is harmful to health.
Inorganic Chemicals - Inorganic chemicals like acids, salts, metals are a result of industrial effluents, household cleansers, and surface run-off and are injurious to health.
Radioactive Materials - Mining and ores processing, power plants, weapons production and natural give rise to radioactive pollution like that of uranium, thorium, cesium, iodine and radon. Radioactive pollution causes serious health diseases to all organisms.
Sediments - Sedimentation of soil, silt due to land erosion and deposition causes disruption in ecosystem.
Plant Nutrients - Nutrients like nitrates, phosphates, and ammonium are let off from agricultural and urban fertilizers, sewage and manure. Excess of nutrients cause eutrophication and affect the ecosystem.
Animal Manure and Plant Residues - These substances in water causes increased algal blooms and microorganism population. This increases oxygen demand of water, affecting aquatic ecosystem. This is introduced into water due to sewage, agricultural run-off, paper mills, food processing etc.
Thermal Pollution - Temperature changes of water caused due to using water as cooling agent in power plants and industries causes increase in water temperature affecting the aquatic life.
The contaminants that lead to water pollution include a wide variety of substance like chemicals, pathogens, temperature changes and discoloration.
- Industrial activity causes huge water pollution. Wastes from factories are let off into freshwater to carry waste from plants into rivers. This contaminates water with pollutants like lead, mercury, asbestos and petrochemicals.
- Sewage let off from domestic households, factories, commercial buildings are untreated in water treatment plants yet are disposed into the sea. Sewage containing flush chemicals and pharmaceuticals causes greater problems.
- Solid waste dumping and littering of cardboard, plastics, glass, styrofoam, aluminium tins, etc., in water bodies.
- Oil spills from tankers and ship travel causes oil pollution. Oil does not dissolve in water and forms a thick layer on the water surface.
- Burning of fossil fuels and emissions from industries and motor vehicles causes formation of acidic particles in the atmosphere. These particles fuse with water vapor resulting in acid rain. Acid rain harms aquatic life.
- Increase in water temperature is a result of global warming and thermal plants use water as cooling agents for mechanical equipments.
Other causes of water pollution:
Detergents, by-productions of disinfection, food processing waste, insecticides, petrochemicals, debris from logging operations, volatile organic compounds, personal hygiene and cosmetic products, drug pollution, chemical wastes, fertilizers, heavy metals, and sedimentation are other causes of water pollution.
Water pollution extensively affects health in humans and aquatic ecosystems.
- Groundwater contamination causes reproductive and fertility disorders in wildlife ecosystems.
- Sewage, fertilizer and agricultural run-off has nutrients, organic substances which lead to increase of algal bloom causing oxygen depletion. The lower oxygen levels affect the natural ecological balance of rivers and lake ecosystem.
- Consumption and swimming in contaminated water causes skin diseases, cancer, reproductive problems, stomach ailments in humans.
- Industrial effluents and agricultural pesticides accumulate in aquatic environments causing harm to aquatic animals and lead to biomagnifications. Heavy metals like mercury, lead are poisonous to small children and women. These chemicals interfere in the development of nervous system in fetuses and young children.
- Rising water temperatures destroy aquatic ecosystem. Coral reefs are bleached due to warmer temperatures. Warmer waters forces indigenous water species to seek cooler water causing ecological shift of the affected area.
- Littering by humans like plastic bags, clog and suffocate aquatic animals.
- Water pollution causes soil erosion in streams, rivers and flooding due to accumulation.