Table of Contents
- 1 Water Pollution
- 2 Causes of Water Pollution
- 3 Ground Water
- 4 Water Pollution Control Measures
- Water pollution is the addition/presence of undesirable substances to/in water such as organic, inorganic, biological, radiological, heat, which degrades the quality of water so that it becomes unfit for use’.
- Water pollution is caused by a variety of human activities such as industrial, agricultural and domestic.
- Natural sources of pollution of water are soil erosion, leaching of minerals from rocks and decaying of organic matter.
- Rivers, lakes, seas, oceans, estuaries and ground water sources may be polluted by point or non-point sources.
- When pollutants are discharged from a specific location such as a drain pipe carrying industrial effluents discharged directly into a water body it represents point source pollution.
- In contrast non-point sources include discharge of pollutants from diffused sources or from a larger area such as run off from agricultural fields, grazing lands, construction sites, abandoned mines and pits, roads and streets.
- Sewage water include discharges from houses, commercial and industrial establishments connected to public sewerage system.
- The sewage contains human and animal excreta, food residues, cleaning agents, detergents and other wastes.
- Domestic and hospital sewage contain many undesirable pathogenic microorganisms, and its disposal into a water without proper treatment.
Putrescibility is the process of decomposition of organic matter present in water by microorganisms using oxygen.
- Presence of organic and inorganic wastes in water decreases the dissolved Oxygen (DO) content of the water.
- Water having DO content below 8.0 mg/L may be considered as contaminated. Water having DO content below. 4.0 mg/L is considered to be highly polluted.
- DO content of water is important for the survival of aquatic organisms. A number of factors like surface turbulence, photosynthetic activity, O2 consumption by organisms and decomposition of organic matter are the factors which determine the amount of DO present in water.
- The higher amounts of waste increases the rates of decomposition and O2 consumption, thereby decreases the DO content of water.
- The demand for O2 is directly related to increasing input of organic wastes and is expressed as biological oxygen demand (BOD) of water.
- Water pollution by organic wastes is measured in terms of Biochemical Oxygen Demand (BOD).
- BOD is the amount of dissolved oxygen needed by bacteria in decomposing the organic wastes present in water. It is expressed in milligrams of oxygen per litre of water.
- The higher value of BOD indicates low DO content of water. Since BOD is limited to biodegradable materials Therefore, it is not a reliable method of measuring pollution load in water.
- Chemical oxygen demand (COD) is a slightly better mode used to measure pollution load in water.
- COD measures the amount of oxygen in parts per million required to oxidize organic (biodegradable and non-biodegradable) and oxidizable inorganic compounds in the water sample.
- The industries discharge several inorganic and organic pollutants, which may prove highly toxic to the living beings.
- Discharge of waste water from industries like petroleum, paper manufacturing, metal extraction and processing, chemical manufacturing, etc., that often contain toxic substances, notably, heavy metals (defined as elements with density > 5 g/cm3 such as mercury, cadmium, copper, lead, arsenic) and a variety of organic compounds.
Type of Industry
|Mining||Chlorides, ferrous sulphate, sulphuric acid, hydrogen sulphide, ferric hydroxide and heavy metals.|
|Iron and Steel||Iron cyanide, thiocyanates, sulphides, oxides of copper, chromium, cadmium, and mercury.||Oil, phenol and naptha|
|Chemical Plants||Various acids and alkalies, chlorides, sulphates, nitrates of metals, phosphorus, fluorine, silica and suspended particles.||Aromatic compounds solvents, organic acids, nitro compound dyes, etc.|
|Pharmaceutical||Proteins, carbohydrates, organic solvent intermediate products, drugs and antibiotics|
|Soap and Detergent||Tertiary ammonium compounds, alkalies (e.g. lime or caustic soda)||Flats and fatty acids, glycerol, polyphosphates, sulphonated hydrocarbons.|
|Paper and Pulp||Sulphides, bleaching liquors.||organic acids.|
- Agricultural runoff contains dissolved salts such as nitrates, phosphates, ammonia and other nutrients, and toxic metal ions and organic compounds.
- Fertilizers contain major plant nutrients such as nitrogen, phosphorus and potassium.
- Excess fertilizers may reach the ground water by leaching or may be mixed with surface water of rivers, lakes and ponds by runoff and drainage.
- Pesticides include insecticides, fungicides, herbicides, nematicides, rodenticides and soil fumigants. They contain a wide range of chemicals such as chlorinated hydrocarbons (CHCs. E.g. DDT, Endosulfan etc.), organophosphates, metallic salts, carbonates, thiocarbonates, derivatives of acetic acid Many of the pesticides are non-degradable and their residues have long life.
- The animal excreta such as dung, wastes from poultry farms, piggeries and slaughter houses etc. reach the water though run off and surface leaching during rainy season.
- Power plants – thermal and nuclear, chemical and other industries use lot of water for cooling purposes and the used hot water is discharged into rivers, streams or oceans.
- Discharge of hot water may increase the temperature of the receiving water by 10 to 15 °C above the ambient water temperature. This is thermal pollution.
- Increase in water temperature decreases dissolved oxygen in water which adversely affects aquatic life.
- Unlike terrestrial organisms, aquatic organisms are adopted to a uniform steady temperature of environment. Sudden rise in temperature kills fishes and other aquatic animals.
- Discharge of hot water in water body affects feeding in fishes, increases their metabolism and affects their growth. Their swimming efficiency declines. Running away from predators or chasing prey becomes difficult. Their resistance to diseases and parasites decreases.
- One of the best methods of reducing thermal pollution is to store the hot water in cooling ponds, allow the water to cool before releasing into any receiving water body
- Nuclear accidents near water bodies or during natural calamities like tsunami and earthquakes poses the risk of radiation leakage (radiation exposure) into water bodies. E.g. Fukushima Daiichi nuclear disaster.
Radiation exposure causes mutations in DNA of marine organisms. If those mutations are not repaired, the cell may turn cancerous.
Radioactive iodine tends to be absorbed by the thyroid gland and can cause thyroid cancer.
- Oil spills are most glaring of all oceanic pollution.
- The most common cause of oil spill is leakage during marine transport and leakage form underground storage tanks. Oil spill could occur during off shore oil production as well.
Impact of oil spill on marine life
- Oil being lighter than water covers the water surface as a thin film cutting off oxygen to floating plants and other producers.
- Within hours of oil spill, the fishes, shellfish, plankton die due to suffocation and metabolic disorders.
- Birds and sea mammals that consume dead fishes and plankton die due to poisoning. Death of these organisms severely damages marine ecosystems.
Impact of oil spills on terrestrial life
- Bays, estuaries, shores, reefs, beaches particularly near large coastal cities or at the mouth of rivers are relatively more susceptible to the hazards of oil spills.
- A number of coastal activities, especially recreational such as bathing, boating, angling, diving, rafting are affected. As a result tourism and hotel business in the coastal areas suffers seriously.
- Plants of water hyacinth are the world’s most problematic aquatic weed, also called ‘Terror of Bengal’.
- They grow abundantly in eutrophic water bodies, and lead to an imbalance in the ecosystem dynamics of the water body.
- They cause havoc by their excessive growth leading to stagnation of polluted water.
- In India at many places, the ground water is threatened with contamination due to seepage from industrial and municipal wastes and effluents, sewage channels and agricultural runoff.
- Pollutants like fluorides, uranium, heavy metals and nutrients like nitrates and phosphates are common in many parts of India.
Q1. Which of the following can be found as pollutants in the drinking water in some parts of India?
Select the correct answer using the codes given below.
- 1 and 3 only
- 2, 4 and 5 only
- 1, 3 and 5 only
- 1, 2, 3, 4 and 5
Easiest option is 3) Fluoride. So, (b) can be eliminated.
Next easiest option is Arsenic (Heavy metal). Damn!
Nest easiest option is Uranium. Many columns are written on uranium mining and its ill-effects. So, (a) also can be elevated. (a) and (b) eliminated. (c) and (d) remains.
The knowledge of either “Sorbitol” or “Formaldehyde” will tell us the answer.
Formaldehyde is more known than sorbitol. Googling didn’t give me any authentic source that called formaldehyde a water pollutant. It is used a preservative to preserve human organs. It finds some application in textile, resign and wood industry.
Answer: c) 1, 3 and 5 only
Sorbitol (glucitol) is a sugar alcohol with a sweet taste which the human body metabolizes slowly.
- Oceans are the ultimate sink of all natural and manmade pollutants.
- Rivers discharge their pollutants into the sea.
- The sewerage and garbage of coastal cities are also dumped into the sea.
- The other sources of oceanic pollution are navigational discharge of oil, grease, detergents, sewage, garbage and radioactive wastes, off shore oil mining, oil spills.
Titbit: 22 March is celebrated as the world water day.
General Assembly of the United Nations proclaimed the period 2005 – 2015 as the International Decade for action on “Water for life”
Natural stores of water in the global hydrological cycle
|Lakes and rivers||0.009|
- The moisture in the soil indicates the presence of water underground.
- If we dig deeper and deeper, we would reach a level where all the space between particles of soil and gaps between rocks are filled with water. The upper limit of this layer is called the water table.
- The water table may be at a depth of less than a metre or may be several metres below the ground. The water found below the water table is called groundwater.
- The process of seeping of water into the ground is called infiltration.
- At places the groundwater is stored between layers of hard rock below the water table. This is known as an aquifer.
- The rainwater can be used to recharge the groundwater. This is referred to as water harvesting.
Mahatma Gandhi said: “No one need to wait for anyone else to adopt a humane and enlightened course of action.”
- Dissolved nitrates commonly contaminate groundwater.
- Excess nitrate in drinking water reacts with hemoglobin to form non-functional methaemoglobin, and impairs oxygen transport. This condition is called methaemoglobinemia or blue baby syndrome.
Methemoglobin is a form of the oxygen-carrying metalloprotein hemoglobin. Methemoglobin cannot bind oxygen, unlike oxyhemoglobin.
- High level of nitrates may form carcinogens and can accelerate eutrophication in surface waters.
- Poor hygiene of wells may cause pathogenic contamination. Water seepage from solid waste dumps and municipal drains may also cause pathogenic contamination.
- Include lead, mercury, cadmium, copper, chromium and nickel. These metals can be toxic and carcinogenic.
- Seepage of industrial and mine discharges, fly ash ponds of thermal power plants can lead to metals in groundwater.
- In India and Bangladesh [Ganges Delta], millions of people are exposed to groundwater contaminated with high levels of arsenic, a highly toxic and dangerous pollutant.
- Chronic exposure to arsenic causes black foot disease. It also causes diarrhoea, peripheral neuritis, hyperkeratosis and also lung and skin cancer.
- Seepage of agricultural runoff loaded with organic compounds like pesticides and may cause pesticide pollution of ground water.
- Excess fluoride in drinking water causes neuromuscular disorders, gastro-intestinal problems, teeth deformity, hardening of bones and stiff and painful joints (skeletal fluorosis).
- Fluorisis is a common problem in several states of the country due to intake of high fluoride content water.
- Fluorides cause dental fluorisis, stiffness of joints (particularly spinal cord) causing humped back.
- Pain in bones and joint and outward bending of legs from the knees is called Knock-Knee syndrome.
- High concentration of fluoride ions is present in drinking water in 13 states of India. The maximum level of fluoride, which the human body can tolerate is 1.5 parts per million (mg/L of water). Long term ingestion of fluoride ions causes fluorosis.
- Due to un-even distribution of rainfall in time and space and ever-increasing demand of water for agricultural, industrial and domestic activities, the water resources are over-exploited. This is resulting in shrinking or even drying up of many water bodies for considerable periods in a year.
- Reducing demands by optimum use, minimization of wastage, efforts to reduce the percolation and evaporation losses, conservation efforts in domestic uses, groundwater recharging, rain water harvesting, afforestation, recycling and reuse are important to combat this problem.
- Water borne diseases are the most important water quality issues in India. This is mainly due to inadequate arrangements for transport and treatment of wastewaters.
- Eutrophication [oxygen depletion due to algal blooms] is a common problem in most of the India lakes and rivers due to discharge of untreated sewage and industrial effluents.
- There are number of cases where salinity is increasing in both surface water and groundwater.
- The increase in groundwater salinity is mainly due to increased irrigation activities or sea water intrusion in coastal areas.
- Due to discharge of toxic effluents from many industries and increased use of chemicals in agriculture and their subsequent contribution to the water bodies, many water bodies in the country are polluted due to presence of toxic substances.
- A large number of areas in our aquatic environment support rare species of aquatic and amphibious plants and animals and are, therefore, ecologically very sensitive. They need special protection.
- Realizing the importance of maintaining the cleanliness of the water bodies, the Government of India has passed the Water (Prevention and Control of Pollution) Act, 1974 to safeguard our water resources.
- An ambitious plan to save the river, called the Ganga Action Plan was launched in 1985. It aimed to reduce the pollution levels in the river. However, the increasing population and industrialization have already damaged this mighty river beyond repair.
- In India, the Central Pollution Control Board (CPCB), an apex body in the field of water quality management, has developed a concept of “designated best use”.
- Accordingly the water body is designated as A, B, C, D, E on the basis of
- dissolved oxygen, mg/1
- BOD, (200C) mg/l
- total coliform (MPN/100ml)
- free ammonia mg/l,
- electrical conductivity etc.
- The CPCB, in collaboration with the concerned State Pollution Control Boards, has classified all the water bodies including coastal waters in the country according to their “designated best uses”.
- This classification helps the water quality managers and planners to set water quality targets and identify needs and priority for water quality restoration programmes for various water bodies in the country.
- The famous Ganga Action Plan and subsequently the National River Action Plan are results of such exercise.
- Riparian buffers: A riparian buffer is a vegetated area (a “buffer strip”) near a stream, usually forested, which helps shade and partially protect a stream from the impact of adjacent land uses. It plays a key role in increasing water quality in associated streams, rivers, and lakes, thus providing environmental benefits.
- Treatment of sewage water and the industrial effluents before releasing it into water bodies. Hot water should be cooled before release from the power plants.
- Excessive use of fertilizers and pesticides should be avoided. Organic farming and efficient use of animal residues as fertilizers can replace chemical fertilizers.
- Water hyacinth (an aquatic weed, invasive specie) can purify water by taking some toxic materials and a number of heavy metals from water.
- Oil spills in water can be cleaned with the help of bregoli — a by-product of paper industry resembling saw dust, oil zapper, microorganisms.
- It has been suggested that we should plant eucalyptus trees all along sewage ponds. These trees absorb all surplus wastewater rapidly and release pure water vapor into the atmosphere.
- Bioremediation is the use of microorganisms (bacteria and fungi) to degrade the environmental contaminants into less toxic forms.
- The microorganisms may be indigenous to a contaminated area or they may be isolated from elsewhere and brought to the contaminated site.
- The process of bioremediation can be monitored indirectly by measuring the Oxidation Reduction Potential or redox in soil and groundwater, together with pH, temperature, oxygen content, electron acceptor/donor concentrations, and concentration of breakdown products (e.g. carbon dioxide)
- In situ — It involves treatment of the contaminated material at the site.
- Bioventing: supply of air and nutrients through wells to contaminated soil to stimulate the growth of indigenous bacteria. It is used for simple hydrocarbons and can be used where the contamination is deep under the surface.
- Biosparging: Injection of air under pressure below the water table to increase groundwater oxygen concentrations and enhance the rate of biological degradation of contaminants by naturally occurring bacteria
- Bioaugmentation: Microorganisms are imported to a contaminated site to enhance degradation process.
Using bioremediation techniques, TERI has developed a mixture of bacteria called ‘Oilzapper and Oilivorous-S’ which degrades the pollutants of oil-contaminated sites, leaving behind no harmful residues. This technique is not only environment friendly, but also highly cost-effective.
Q2. Recently, ‘oilzapper’ was in the news. What is it?
- It is an eco-friendly technology for the remediation of oil sludge and oil spills.
- It is the latest technology developed for under- sea oil exploration.
- It is a genetically engineered high biofuel yielding maize variety.
- It is the latest technology to control the accidentally caused flames from oil wells.
Answer: a) Current Affairs based question. Keep track of latest developments.
- Ex situ — involves the removal of the contaminated material to be treated elsewhere.
- Land farming: contaminated soil is excavated and spread over a prepared bed and periodically tilled until pollutants are degraded. The goal is to stimulate indigenous biodegradative microorganisms and facilitate their aerobic degradation of contaminants.
- Biopiles: it is a hybrid of land farming and composting. Essentially, engineered cells are constructed as aerated composted piles. Typically used for treatment of surface contamination with petroleum hydrocarbons.
- Bioreactors: it involves the processing of contaminated solid material (soil, sediment, sludge) or water through an engineered containment system.
- Composting: Composting is nature’s process of recycling decomposed organic materials into a rich soil known as compost.
Advantages of bioremediation
- Useful for the complete destruction of a wide variety of contaminants.
- The complete destruction of target pollutants is possible.
- Less expensive.
- Environment friendly.
Disadvantages of bioremediation
- Bioremediation is limited to those compounds that are biodegradable. Not all compounds are susceptible to rapid and complete degradation.
- Biological processes are often highly specific.
- It is difficult to extrapolate from bench and pilot-scale studies to full-scale field operations.
- Bioremediation often takes longer time than other treatment process.
- Phytoremediation is use of plants to remove contaminants from soil and water. Natural phytoremediation is carried out by mangroves, estuarine vegetation and other wetland vegetation.
- Phytoextraction/phytoaccumulation: plants accumulate contaminants into the roots and aboveground shoots or leaves.
- Phytotransformation/phytodegradation: uptake of organic contaminants from soil, and their transformation to more stable, less toxic, less mobile form.
- Phytostabilization: plants reduce the mobility and migration of contaminated soil. Leachable constituents are adsorbed and bound into the plant structure.
- Rhizodegradation: breakdown of contaminants through the activity existing in the rhizosphere (region of soil in the vicinity of plant roots). This activity is due to the presence of proteins and enzymes produced by the plants or by soil organisms such as bacteria, yeast, and fungi.
- Rhizofiltration: water remediation technique that involves the uptake of contaminants by plant roots. Rhizofiltration is used to reduce contamination in natural wetlands and estuary areas (E.g. Mangroves).
- Mycoremediation: fungi are used to decontaminate the area.
- Mycofiltration: using fungal mycelia to filter toxic waste and microorganisms.
- The bacterium Deinococcus radiodurans has been used to detoxify toluene and ionic mercury which are released from radioactive nuclear waste.