Environmental Science

LESSON 22. Water Pollution

Two types of pollutions :

Point source of pollution: This source of pollution can be readily identified because it has a definite source and place, where it enters the water. Eg: Municipal industrial discharges pipes.

Non point source of pollution: when a source of pollution cannot be readily identified such as agricultural run off, acid rain etc, it is called as non point source of pollution.

Causes of water pollution: (surface water)

• Disease causing agents parasitic worms, bacteria, viruses, protozoa that enter water from domestic sewage and untreated human and animal wastes.

• Oxygen depleting wastes: These are organic wastes that can be decomposed by aerobic bacteria. The amount of oxygen required to break down a certain amount of organic matter is called BOD. It is an indicator of level of pollution.

• Inorganic plant nutrients : There are water soluble nitrates and phosphates

• Excess pesticides: For control of pest pesticides are used in discriminately. These fall on ground and leach with rain water to canals and rivers.

• Water soluble organic chemicals: These are acids, salts and compounds of toxic metals such as mercury & lead.

• Variety of organic chemicals: includes oil, gasoline, plastics, pesticides, detergents & many other chemicals.

• The sediments of suspended matter: Occur when soil is eroded.

• Water soluble radio active isotopes: Enter the water courses along with rain water.

• Hot water released by power plants & industries that use large volume of water to cool the plant results in a rise in temp of local water bodies.

• Acid drainage into rivers.

Ground water pollution: A greater threat to human life comes from the pollution of ground water which is used for drinking and irrigation being polluted.

Causes of ground water pollution:

1. Urban runoff of untreated or poorly treated waste water storage and garbage

2. Industrial waste storage located above or near aquifer

3. Agricultural practices such as application of large amounts of fertilizers and pesticides, animal feeding operations etc in rural sector

4. Leaks from under ground storage tanks containing gasoline and other hazardous substances

5. Leachate from land fills

6. Poorly designed and inadequately maintained septic tanks

7. Mining waters

Case study:Cashew in Kasargod, Kerala poisonous nuts

Endosulfan, a pesticide banned by many countries in the world including India

was extensively sprayed aerially in the cashew plantations of Plantation Corporation of Kerala (PCK) spread over 2209 hectares in various divisions of Kasargod district, Kerala. Endosulfan is slated to be phased out globally under the Stockholm Convention 2001, to which India is a signatory. The pesticide is classified as an organochlorine compound and its breakdown products are persistent in the environment, with an estimated half-life of nine months to six years. It is known to ACID MINE DRAINAGE INTO THE RIO TINTO RIVER potentially bioaccumulate in humans and other animals, in the liver, kidneys and fatty tissue. PCK started using this pesticide in 1979 and unusual health disorders were reported from places like Vaninagar, Adur, Mulleria, Padre etc. The people were unaware that this was a lethal poison. A study conducted by the Centre for Science and Environment (CSE) confirmed the presence of high quantities of endosulfan in the samples of water, soil, fruits, mother’s milk and blood in Kasargode. Further disorders of the central nervous system, cerebral palsy, mental and physical retardation, epilepsy and congenital anomalies like stag horns, liver cancer, blood cancer, infertility, miscarriages, hormonal imbalances, skin diseases and asthma have been reported. All these disorders were traced to endosulfan effects. After mass agitations and several reports by various agencies, the use of endosulfan was banned in Kerala in August 2001. Though, the state government has paid compensations, the rehabilitation of the living victims is really tough and challenging. Reports reveal that approximately, 224 people were critically affected and 226 have a 60 per cent disability. This tragedy was spread over 20 villages in the state. (Ref: Sushmitha Baskar and .R.Baskar)

Effects of Water pollution:

1. Large amount of human waste in water increase the number of bacteria such as Escherichia coli and streptococcus sps which cause gastro intestinal diseases.

Water borne diseases diarrhea, typhoid etc.

2. If more organic matter is added to water the O2 is used up. This causes fish and other forms of O2 dependent aquatic life dies.

3. Eutrophication due to inorganic pollutants.

4. Excess pesticides cause Biomagnification.

5. High levels of organic chemicals (acids, salts& toxic metals) can make the water unfit to drink, harm fish and other aquatic life, reduce crop yields

6. Variety of organic chemicals / oil gasoline, plastics detergents) are harmful to aquatic life and human life

7. Sediments (erosion), clog the lakes and artificial reservoirs

8. Radioisotopes cause birth defects, cancer and genetic damage.

9. Hot water cause thermal pollution

10. Hot water because of thermal pollution not only decrease the solubility of O2 but also changes the breeding cycles of various aquatic organisms.

11. Accidental oil spills cause environmental damage.

12. Minamata disease is caused due to mercury poisoning of water.

13. Fluorine contamination in drinking water causes Fluorosis, NO3 contamination causes Blue baby disease (Methaemoglobinaceae) and PO4 contamination causes bone marrow disease.

14. Arsenic poisioning is the major effect mostly in West Bengal. Arsenicosis or

arsenic toxicity develops after 2-5 years exposure to arsenic contaminated drinking water.

Eutrophication The term “eutrophic” means well-nourished; thus, “eutrophication” refers to natural or artificial addition of nutrients to bodies of water and to the effects of the added nutrients. When the effects are undesirable, eutrophication may be considered a form of pollution (National Academy of Sciences, 1969). Nixon (1995) defined it as an increase in the rate of supply of organic matter in an ecosystem. It is the process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates. These typically promote excessive growth of algae. As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish. Similarities include subsequent negative environmental effects such as anoxia, and severe reductions in water quality, fish and other animal populations may occur. Other species may experience an increase in population that negatively affects other species in the direct ecosystem. In simpler terms it is the bloom of phytoplankton in a water body. It is often the result of anthropogenic pollution with nutrients, particularly the release of sewage effluent and agricultural run-off carrying fertilizers into natural waters. However, it also occurs naturally in situations where nutrients accumulate (e.g. depositional environments) or where they flow into systems on an ephemeral basis. Eutrophication generally promotes excessive plant growth and decay, favours simple algae and plankton over other more complicated plants, and causes a severe reduction in water quality. In aquatic environments, enhanced growth of choking aquatic vegetation or phytoplankton (eg: algal blooms) disrupts normal functioning of the ecosystem, causing a variety of problems such as a lack of oxygen in the water, needed for fish and shellfish to survive. The water then becomes cloudy, coloured a shade of green, yellow, brown, or red. Human society is impacted as well: eutrophication decreases the resource value of rivers, lakes, and estuaries such that recreation, fishing, hunting, and aesthetic enjoyment are hindered. Health-related problems can occur where eutrophic conditions interfere with drinking water treatment.

Biomagnification, also known as bioamplification or biological magnification, is the increase in concentration of a substance, such as the pesticide DDT, that occurs in a food chain as a consequence of:

• Persistence ( can't be broken down by environmental processes)

• Food chain energetics

Low (or nonexistent) rate of internal degradation/excretion of the substance (often due to water-insolubility). Biological Magnification often refers to the process whereby certain substances such as pesticides or heavy metals move up the food chain, work their way into rivers or lakes, and are eaten by aquatic organisms such as fish, which in turn are eaten by large birds, animals or humans. The substances become concentrated in tissues or internal organs as they move up the chain. Bioaccumulants are substances that increase in concentration in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted. For example, though mercury is only present in small amounts in sea water, it is absorbed by algae (generally as methyl mercury. Bioaccumulation and bioconcentration result in buildup in the adipose tissue of successive trophic levels: zooplankton, small nekton, larger fish etc. Anything which eats these fish also consumes the higher level of mercury the fish have accumulated. This process explains why predatory fish such as swordfish and sharks or birds like osprey and eagles have higher concentrations of mercury in their tissue than could be accounted for by direct exposure alone. For example, herring contains mercury at approximately 0.01 ppm and shark contains mercury at greater than 1 ppm (EPA 1997).

Case study of groundwater pollution in India - An example of groundwater pollution caused by excessive extraction is that of fluoride contamination. It has spread across 19 states and across a variety of ecological regions ranging from the Thar desert, the Gangetic plains and the Deccan plateau. Source: When the bedrock weathers the fluoride leaches into water and the soil. surfaced during the last three decades - extraction of groundwater which has resulted in the tapping of aquifers with high fluoride concentrations was noticed during 1970s and the 1980s when there was massive state investment in rural water development for irrigation as well as for drinking. Encouraged by state subsidies on diesel and electricity, people invested in diesel and submersible pumps in a bid to extract groundwater through borewells.

This policy aggravated the fluoride problem. Effects: combines with the bones as it has an affinity for calcium phosphate in the bones. Excess intake of fluoride can lead to dental fluorosis, skeletal fluorosis or non-skeletal fluorosis. Correction: -

Deflouridation plants and household water treatment kits are stop-gap solutions.

(Ref: Sushmitha Baskar & R.Baskar)

Control measures of water pollution:

• Setting up of effluent treatment plants to treat waste water can reduce the pollution load in the recipient water. The treated effluent can be reused either for gardening or cooling purposes or wherever possible.

• Root zone process has been developed by Thermax. by running contaminated water through the root zone of specially designed reed beds. These have the capacity to absorb from the surrounding air through their stomata openings. It creates O2 rich conditions where bacteria and fungi oxidize the wastes.

• Providing sanitation and waste water treatment facility.

• Integrated nutrient management (INM) and integrated pest management (IPM) practices will reduce the effects caused due to excess pesticides.

Root zone treatment Technology for sewage

The process in a root zone system to treat the sewage is very simple to explain yet complex in nature. Raw effluent (after removing grit or floating material is passed horizontally or vertically through a bed of soil having impervious bottom. The effluent percolates through the bed that has all the roots of the wetland plants spread very thickly . Nearly 2,500 types of bacteria and 10,000 types of Fungi, which harbor around roots get oxygen from the weak membranes of the roots and aerobically oxidize the organic matter of the effluent. The characteristics of plants of absorbing oxygen through their leaves and passing it down to roots through their stems which are hollow, is utilized as a bio-pump. Away from the roots, anaerobic digestion also takes place. The filtering action of the soil bed, the action with fungi etc. and chemical action with certain existing or added inorganic chemicals help in finally obtaining a very clear and clean water. The system of plants regenerates itself as the old plants die and form useful humus. Hence the system becomes maintenance free and can run upto 50 to 60 years without any loss of efficiency as has been described.

Reed bed is one of the natural and attractive methods of treating domestic, industrial and agricultural wastes. A reed bed is an engineered method of purifying polluted water as it passes through artificially constructed wetland area, usually containing common reeds. Reed bed is considered as an effective and reliable secondary and tertiary treatment method where land area is not a major constraint. Generally reed bed is made in shallow pits, installed with a drain pipe in a bed of pieces of lime stones and filled up with pebbles, iron filings and graded sand. In this sandy body, reed plants (with hollow root which bring oxygen into the filter bed)are planted It is advantageous to treat the sewage by root zone system. It achieves the standard for tertiary level treatment standard with no operating cost. There is no chemical used for pH adjustment or for flocculation. Low electricity is consumed for pumping treated water from the collection tank to the reed bed. From the reed bed the treated water is collected and used for irrigation by gradient flow.

The root zone system has low maintenance cost since it involves no machinery and its associated maintenance. It requires negligible attendance for operation and monitoring. It has no sludge handling problem such as scraping of slurry from the sludge drying beds and its disposal twice in a week.

The sludge gets mineralized in the vertical zone of the reed bed .The sludge

mineralizing beds needs to be disposed once in 10 or 15 years.

• It enhances the landscape and gives the site a green appeal.

• It provides natural habitat for birds and after a few years gives an appearance of a Bird´s sanctuary.

• It is though an effluent treatment plant, it does not have odour problem and though it is a green zone, it does not have mosquitoes problem.

• The reeds are not grazed by ruminants.

• Salinity may not be a problem for a survival or operations of reed beds.

• It is recommended to combine vertical flow and then horizontal flow of sewage with a soil having impervious bottom.

• In the horizontal flow system, the sewage percolates through bed and that has allroots of the wetland plants spread very thickly nearly with 2500 types of bacteria and 10,000 types of fungi and aerobically oxidized organic matter of the effluent.

• Root zone system gives a very good performance of removing 90% BOD and 63% Nitrogen.

• Phragmites australis has been found more efficient in nitrogen removal compared to Typha latifolia.

However, compared to the conventional treatment processes such as activated sludge, aerated lagoons, waste stabilization pond etc the performance of the root zone treatment system is good with regard to the removal or reduction of BOD, COD, TOC and Total coliforms

(http://wasterecycleinfo.com/sewage.html)