Water Pollution Essay-The difficulty in defining water pollution lies in the fact that virtually no water is found on the earth in its absolutely purest form. There are various impurities such as dissolved gases, minerals, suspended matter like clay, silt, sand, etc., besides microbes. But beyond a certain level, these could cause harm to the ecology. According to the definition of the World Health Organisation (WHO) (1966), water pollution occurs when “foreign materials either from natural or other sources are contaminated with water supplies and may be harmful to life, because of their toxicity, reduction of normal oxygen level of water, aesthetically unsuitable effects and spread of epidemic diseases”.
Sources water pollution
The major sources of water pollution are (i) industrial effluents, (ii) industrial wastes derived from chemical industries, thermal power plants and nuclear power stations, (iii) sewage and other waste, and (iv) agricultural discharges.
Types of water pollution
Three major types of pollution of freshwater are: (i) excess of nutrients from sewage and soil erosion causing algae blooms, (ii) pathogens from sewage which spread disease, and (iii) heavy metals and compounds which bioaccumulate in aquatic organisms.
On the basis of sources of pollution, water pollutants may be considered under the following categories.
(a) Industrial pollutants: chlorides, sulphides, carbonates, nitrates, heavy metals, various organic chemical compounds, etc.
(b) Agricultural pollutants: chemical fertilisers, insecticides, pesticides, etc.
(c) Urban pollutants: sulphates, nitrates and potassium contained in urban sewage water, chemical ions and bicarbonate ions derived from lime and fertilisers used in gardens, and chlorine and sodium ions contained in salts used for melting ice which covers roads and buildings in the cities of temperate countries.
(d) Domestic sewage refers to waste water that is discarded from households containing impurities such as organic materials and plant nutrients that tend to rot; the main organic materials are food and vegetable.
On the basis of physical and chemical properties, water pollutants could be (a) physical pollutants like various chemicals, colours, sediments, volcanic dust etc. dissolved or suspended in water, and (b) chemical pollutants like sulphides, chlorides, carbonates, nitrates, etc.
In India, water pollution is commonly caused by the following activities.
Phosphorus from household waste water and sewage comes from detergents and stays in rivers for a long time where it takes up valuable oxygen Only few sewage systems are equipped to remove phosphates.
People dispose of solid waste, plastic bags and flower garlands into rivers and other surface water bodies.
Incidentally, the main source of pollution in Indian rivers is municipal waste.
People defecating in open and near water bodies contribute to river and other water pollution Often animals are allowed to be washed on just wallow in water bodies.
The practice of dumping human remains in rivers also poses health threats especially as the rate at which partially burned bodies are dumped in rivers has become unsustainable. Besides pollution, the situation may cause infectious diseases to spread.
Water pollutants may also be divided into (a) degradable or organic pollutants such as sewage. leaf litters, plants and animals which disintegrate, and (b) non-degradable pollutants, mainly toxic solid substances such as plastics.
Indicators of Water Pollution
The most well-established indicator of water quality is oxygen. Dissolved oxygen is needed for the survival of all aquatic organisms. Oxygen affects a vast number of other water indicators, besides the biochemical indicator, odour, clarity and taste are also affected by oxygen.
Dissolved oxygen is the amount of free oxygen dissolved in water, expressed in mg per litre, parts per million (ppm), or in per cent of saturation, i.e., where saturation pertains to the maximum amount of oxygen that can be dissolved theoretically in water at a particular altitude and temperature. A high or a low concentration of free oxygen in an aquatic habitat affects the water.
Quality as well as the organisms in it. Thus, this parameter is often measured in order to determine the quality of water and assess its ability to support life. The level of free oxygen dissolved in water is affected by water temperature, pressure, and biological activity
The amount of oxygen required by aerobic microorganisms to decompose the organic matter in a sample of water, such as that polluted by sewage, is called biochemical oxygen demand or biological oxygen demand (BOD). It is used as a measure of the degree of water pollution More specifically, in environment science, BOD is the amount of oxygen, in mg per litre of water, absorbed by a sample kept at 20 °C for five days.
Coliforms are a broad class of bacteria found in our environment; they are found in plant and soil material and are always present in the digestive tracts of warm blooded animals, including humans, and are found in their faeces. The most basic test for bacterial contamination of a water supply is the test for total coliform bacteria count.
Total coliforms include bacteria that are found in the soil, in water that has been influenced by surface water, and in human or animal waste. Faecal coliforms are the group of the total coliforms that are considered to be present specifically in the gut and faeces of warm-blooded animals. Because the origins of faecal coliforms are more specific than the origins of the more general total coliform group of bacteria, faecal coliforms are considered a more accurate indication of animal or human waste than the total coliforms. Escherichia coli (E.Coli) is the major species in the faecal coliform group. Of the five general groups of bacteria that comprise the total coliforms, only E. coli is generally not found growing and reproducing in the environment. Consequently, E. coli is considered to be the species of coliform bacteria that is the best indicator of faecal pollution and the possible presence of pathogens.
When a river or water body is polluted by faecal material, pathogenic bacteria, viruses, and parasites may be introduced, posing a health hazard to those who come in contact with the water. Testing water for specific organisms is limited to investigating specific waterborne disease outbreaks. Coliform bacteria are used as water quality indicators as coliforms may be associated with the sources of pathogens contaminating water, and the analysis of drinking water for coliforms is relatively simple, economical and efficient.
Controlling Water Pollution
Both citizens and the government have to do their bit in controlling pollution; this is in the interest of the people of this country. If the people have a fundamental duty to protect the environment, the government is meant to protect the welfare of the people.
The towns and cities should have facilities to clean the sewage effluent. All towns and cities must have sewage treatment plants (STPs) to clean up the sewage.
Proper drainage and sewage systems should be put in place that will not allow the polluted water to mix with river or ground water.
Industries should install equipment to remove contaminants from their effluents and wastewater. Effluent treatment plants (ETP) should be put in place so as to control pollution at the source itself.
Farmers should use less of chemical fertiliser and pesticides in farming and should adopt organic methods of farming.
Many of our religious practices that pollute water bodies should be minimised or strictly regulated
Washing clothes on river banks or having dhobi ghats alongside the river should be banned. At an individual level there is not much one can do except restrain oneself from throwing waste near or into water bodies. However, one can organise or participate in groups that work to clean up local water bodies. Besides, one can organise awareness campaigns on the issue of river pollution and its threats and distribute literature on the causes and ill effects of water pollution. Even at the family and friends level one can discuss the matter and put a stop to careless treatment of water bodies by individuals.
Thermal pollution is the degradation of water quality by any process that changes ambient water temperature. It is commonly caused by the use of water as a coolant by power plants and industrial manufacturers. When water used as a coolant is returned to the natural environment at a higher temperature, the change in temperature decreases oxygen supply, and affects ecosystem composition, Urban runoff-stormwater discharged to surface waters from roads, for example, can also be a source of elevated water temperatures. Increases in ambient water temperature also occur in streams where shading vegetation along the banks is removed or where sediments have made the water more turbid. Both of these effects allow more energy from the sun to be absorbed by the water and thereby increase its temperature. There are also situations in which the effects of colder-thannormal water temperatures may be observed. For example, the discharge of cold bottom water from deep-water reservoirs behind large dams has changed the downstream biological communities in some systems.
The primary effects of thermal pollution are direct thermal shock, changes in dissolved oxygen, and the redistribution of organisms in the local community. Because water can absorb thermal energy with only small changes in temperature, most aquatic organisms have developed enzyme systems that operate in only narrow ranges of temperature. These organisms can be killed by sudden tolerance limits of their metabolic systems.
Small chronic changes in temperature can also adversely affect the reproductive systems of these organisms and also make them more susceptible to disease. Cold water contains more oxygen than hot water so increases in temperature also decrease the oxygen-carrying capacity of water. Raising the water temperature also increases the decomposition rate of organic matter in water, which also depletes dissolved oxygen. These decreases in the oxygen content of the water occur at the same time that the metabolic rates of the aquatic organisms, which are dependent on a sufficient oxygen supply, are rising because of the increasing temperature.
Effects of Water Pollution
Drinking polluted water can cause cholera or typhoid infections, along with diarrhoea. The consumption of highly contaminated water can cause injury to the heart and kidneys. Toxins within water can harm aquatic organisms, thus breaking a link in the food chain. Urea, animal manure and vegetable peelings are food for algae. Algae grow according to how much waste is in a water source. Bacteria feed off the algae, decreasing the amount of oxygen in the water. The decreased oxygen causes harm to other organisms living in the water. The erosion of soil into waterways causes flooding, especially with heavy rainfall. Birds that get into oil-contaminated water die from exposure to cold water and air due to feather damage. Other animals are affected when they eat dead fish in contaminated streams. The effects of water pollution are not always immediate. They are not always seen at the point of contamination.
Contamination of groundwater takes place through pollutants like nitrates, phosphorus, potash, insecticides, pesticides, etc. derived from industries, agricultural fields, urban and rural garbage, contaminated ponds, tanks, etc.
Factors such as the lithology of sub-soils, the nature of aquifers, the amount and nature of rainfall, the depth of the water table, the rate of rainwater infiltration and the infiltration of static water of ponds and lakes control the nature and extent of groundwater pollution. Sometimes groundwater is caused by excessive pumping, which causes the formation of underground cavities through which saline marine water leaks in.
Groundwater pollution causes diseases like cholera, jaundice, typhoid, dysentry, etc. which sometimes assume the proportion of epidemics, i the water is used for drinking, particularly in the developing countries of Asia and Africa. Some of the rare diseases, like ‘minamata’, are caused by mercury contamination.
The presence of toxic chemicals in groundwater causes death of organisms living in lakes, ponds and oceans, if this water finds its way into surface waters. Soil fertility is decreased by contamination of soil if polluted water is used for agricultural purposes.
In India, fresh water in general is slightly alkaline with a pH usually more than 7. Unlike surface waters, subsurface water varies widely from place to place. In coastal Tamil Nadu, intrusion of sea water into the subsurface aquifer makes ground water saline. As ground water is drawn to an excess, the water table falls deeply, and this allows sea water to percolate. This is a problem in Gujarat also. However, the salinity of ground water depends on other dissolved solids. Health concerns have been aggravated due to high fluoride and/or arsenic content of some ground water Wells in several districts in West Bengal, and the mining districts of Khetri and Zawar in Rajasthan have high levels of dissolved arsenic. Ajmer in Rajasthan and Anantpur in Andhra Pradesh are two regions with high fluoride content in ground water, and this causes fluorosis.
The problem of Arsenic and Fluorides in Groundwater
In many areas of the world, there is a natural high concentration of arsenic in groundwater at deeper levels.
In India, where groundwater is used intensively for irrigation and industrial purposes, its over-exploitation is causing aquifer contamination in certain instances, while in certain others its unscientific development with insufficient knowledge of groundwater flow dynamic and geo-hydrochemical processes has led to its mineralisation.
Use of tubewells for water supply in the Ganges Delta; the use of this water causes serious arseni poisoning to large numbers of people. The problem occurs in other places in the world as well; majo incidents have been reported from Thailand Taiwan, and Mainland China, Argentina and Chile There are also many locations in the United State where the groundwater contains arseni concentrations in excess of the US prescribed standard. The acceptable level as defined by WHO for maximum concentrations of arsenic in safe drinking water is 0.01 mg/litre. In India, the permissible level is 0.05 mg/litre.
Arsenic is not often present in its elementa state but is more common in sulphides and sulphosalts. Arsenic is used in industry as a wood preservative and in paints, dyes, metals, soaps insecticides and semi-conductors. Apart from it natural occurrence it is also released into the environment through burning fossil fuels, paper production, cement manufacturing and mining activities.
Arsenite (+3) and arsenate (+5) are the most prevalent toxic forms of inorganic arsenic that are found in drinking water. Intake of drinking water having arsenic concentration beyond the permissible limit of 0.05 mg/lit has deleterious effects on human health; it can cause cardiovascular (hear failure) problem, gastrointestinal problems (burning lips, painful swallowing, thirst, nausea, and severe abdominal colic), hematological effects (anemia and leucopoenia), hepatic effects, renal effects, neurological effects (headache, lethargy, mental confusion, hallucination, seizures and coma), derma effects (skin disorder, hyperkeratosis), carcinogenic effects ( lung cancer), etc.
The source of sediments containing arsenic deposited within the last 2000 years in the West Bengal region could be from northern Himalayan provinces, metamorphic terrain of the Chotanagpur plateau the meta-sedimentary rocks of Eastern Himalaya. Easterly flowing river cutting across Raniganj and other coalfields might also be responsible for bringing arsenic minerals from the mine workings
The incidence of fluoride above permissible levels of 1.5 ppm occur in many Indian states, the prominent of them being Andhra Pradesh, Bihar, Gujarat, Haryana, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Odisha, Punjab, Rajasthan, Tamil Nadu, Uttar Pradesh and point pollution caused by fertilizers and pesticides used in agriculture, often dispersed over large areas, is a great threat to fresh groundwater ecosystems. Intensive use of chemical fertilizers in farms and indiscriminate disposal of human and animal waste on land result in leaching of the residual nitrate causing high nitrate concentrations in groundwater. The presence of fluoride in water cannot be detected without the help of equipment to test water quality. High fluoride content is often detected from such symptoms on human beings as yellowing of teeth, damaged joints and bone deformities, which occur from long years of exposure to fluoride containing water. Due to this reason, by the time the community realises the menace, a large section of the population is already affected.
Water Pollution by Mercury
Some of the sources of mercury pollution include metal smelting, chlorine chemical plants, cement plants, and coalfired power plants. Power plants are the largest source, and facilities that recycle auto scrap are another big source of mercury pollution. Chlorine plants, which use massive quantities of mercury to extract chlorine from salt, ‘lose’ mercury when mercury volatilises during maintenance and other operational activities.
Coal is naturally contaminated with mercury, and when it is burned to generate electricity, mercury is released into the air through the smokestacks. The bulk of this mercury pollution could be eliminated with the installation of pollutioncontrol devices.
Mercury is unique among metals in that it can evaporate when released to water or soil. Also, microbes can convert inorganic forms of mercury to organic forms which can be accumulated by aquatic life.
Mercury contamination in India is reaching alarming levels largely due to the discharge of mercury-bearing industrial effluents ranging from 0.058 to 0.268 milligram/litre (mg/1). This is several times more than the prescribed Indian and WHO standards of 0.001 mg/1 (for drinking water and 0.01 mg/1 (for industrial effluents).
High levels of mercury in fish stocks have been found, mainly in coastal areas. Mumbai, Kolkata, Karwar (in Karnataka) and North Koel (in Bihar) are some of the severely affected areas
detected from across the country: Delhi, Mumbai Vadodara, Vapi, Ankleshwar, Bhopal, Panipat Singhrauli, Ganjam, Dhanbad, Durgapur, Howrah, Medak and many other places. Levels higher than the permissible limits were found near chlor-alkali, cement and chemical units and thermal power plants. The chlor-alkali sector, the biggest known consumer of mercury in India,
Mercury is poisonous in all forms—inorganic, organic or elemental . Methyl mercury is a neurotoxicant: it can damage the developing brain as it crosses the placental and blood-brain barriers easily. The threat to the unborn is, therefore, of particular concern. It can also trigger depression and suicidal tendencies, paralysis, kidney failure Alzheimer’s disease, speech and vision impairment allergies, hypospermia and impotence. Even miniscule increases in methyl mercury exposures may adversely affect the cardiovascular system, says the UNEP’s Global Mercury Assessment report . It is also a possible carcinogen for humans.
On the other hand, while mercury is a socalled persistent pollutant, meaning that it does not break down as some other pollutants do, its dangers lessen considerably over time, because it eventually settles into the beds of rivers, lakes and oceans and is covered over by successive layers of sediment. At some point, fish stop consuming the mercury so eventually it ceases to be a hazard to humans.
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