27 Water Pollution-I (Surface and Groundwater Pollution)

Hardeep Rai Sharma

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Objectives

 

1.  What is water pollution?

2.  To understand surface and groundwater pollution

3.  To know different types of water pollutants

4.  To understand different sources of water pollution

 

Introduction: General details i.e. importance, characteristics, and uses of water are discussed in first module of this paper while water resources in India are mentioned in second module. Therefore in this module we will describe and understand about water pollution. In simple words, an undesirable change in physical, chemical and biological characteristics of water that makes it unfit for designated use in its natural state. As per UNESCO (1992), introduction of any substance into water in undesirable concentration not normally present in water, e.g. microorganisms, chemicals, waste or sewage, which renders the water unfit for its intended use is termed as water pollution. Based upon the type of water resource, water pollution can be divided into surface, ground and marine pollution. Pollutants can be contributed through natural and anthropogenic (manmade) activities. Based upon types of pollutants, water pollution can be fluoride pollution (due to fluoride), arsenic pollution (due to arsenic), thermal (due to discharge of hot water) etc. Marine and thermal pollution are discussed in detail in next modules (no 28 and 29). Based upon the entry of pollutants in waterways sources of pollution can be divided into two categories viz. Point source i.e. pollution source which have specific location usually through pipes and sewers. Point source includes sewage treatment plants, factories, mines and off-shore oil drilling rigs. Non point sources i.e. pollution source are diffuse and discharges pollutant over a wide area through run off from urban and agricultural land, feedlots, and construction sites.

 

The ground water contamination is nearly associated with result of human activities. In the areas having high population density and intensive human land use, ground water is especially vulnerable. Ground water pollution is even greater concern, as we mainly concentrate on pollution of surface water- lakes, rivers and streams. The contaminants in ground water are not diluted and washed away as in case of fast flowing rivers. The pollutants remain in the water for a very long period. It is difficult and expensive to clean up the ground water. In general, the quality of ground water meets safe drinking water standard without any purification or treatment and directly used for human consumption. However, it has been pointed out that 60% of all the districts in India have issues related to availability and quality of ground water or both. The commonly observed contaminants in ground water include arsenic, fluoride, nitrate and iron are geogenic in nature. Other contaminants include bacteria, phosphate and heavy metal which are the result of human activities, it includes domestic sewage, agriculture practices and industrial effluents (Planning Commission, 2013). In 2015, 663 million people lack improved drinking water sources and 2.4 billion people lack improved sanitation (WHO/UNICEF, 2015). Water, hygiene and sanitation was responsible for 842 000 deaths from diarrhea in 2012 (WHO, 2018).

 

For better understanding and clarity the surface and groundwater pollutants are described in separate sections, however some pollutants and sources can be similar for both sources.

 

Surface Water Pollutants

 

They can be classified into:

  1. Organic pollutants i.e. oxygen demanding wastes, sewage, synthetic organic compounds, disease causing agents and oil.
  2. Inorganic pollutants include inorganic salts, mineral acids, finely divided metals or metal compounds, trace elements, sediments and salts.
  3. Agricultural discharges include nutrients, fertilizers and pesticides.
  4. Industrial effluents or waste water from different types of industries.
  5. Waste heat from the industries which causes thermal pollution.
  6. Radioactive pollutants.
  7. Water withdrawal (not a pollutant but an activity)

 

1.    Organic pollutants: This group includes oxygen demanding wastes, domestic waste, animal or food processing plant wastes, oil etc. It includes human excreta, paper, cloths, soap, detergents; waste from paper and pulp industries, tanneries, slaughter houses, meat packing, dairy industry etc. Uncontrolled dumping of wastes into water bodies result into depletion of dissolved oxygen and loss of self-regulatory capability of water. The self purifying capacity of water is lost and water becomes unfit for drinking and other uses. Since decomposition of sewage and other wastes is largely an aerobic process, accumulation of these wastes in water increases it oxygen requirements (BOD). Most of the natural water systems require 5‒6 ppm to support a diverse population (Cleveland and Grable, 1998). Decrease in this dissolved oxygen value is an index of pollution mainly due to organic matter. The waste from animals and humans those are infected with pathogen (disease causing agents) if contaminate water supply can cause outbreak of disease and sometime epidemics. Effluent disposal from septic tank is a potential source of foul smell, mosquito breeding and health hazards.

 

The presence of coliform in Indian rivers indicates that the water is being contaminated with the fecal material of humans, livestocks, pets and other animals. The most probable number(MPN)/100 ml of 1.7 million‒2.6 billion was found in river Yamuna whereas it was 1.1‒2.5 million (Ganges), 2.8 million (Sabarmathi), 24,000‒240,000 (Brahmaputra), 28,000‒ 160,000 (Kaveri), 60,000‒90,000 (Brahmini) 3500‒35,000 (Satluj), 10,000‒33,300 (Krishna), 17,000‒30,000 (Mahanadi), 11,000‒22,000 (Baitarni) and 3640‒5260 (Godavari) rivers of India (Bhardwaj, 2005; Kumar et al., 2005; CWC, 2008). Transmission of diseases takes places when people drink or swim in contaminated aquatic bodies. The contaminated water can contain many bacteria, viruses, protozoa, parasitic worms and other infectitious agent that can cause human and animal diseases. Table 1 shows different types of water borne diseases.

 

Detergents are compounds that relax the surface tension of water and produce foam. Phosphates are the major ingredient of most detergents. They favour the luxuriant growth of algae which form water blooms. This extensive growth of algae consumes most of the available oxygen from water. The decrease in O2 level is harmful to growth of other organisms which produces a foul smell upon decay. The small detergent concentrations of 0.05‒0.1 mg/l in river water are enough to mobilize toxic materials that are adsorbed on sediments (Fellenberg, 2000). The majority of the Indian lakes are under severe threat from nutrient overloading and eutrophication and severe weed growth on the water column (Kurunthachalam, 2013). The dissolved oxygen (DO) level in Yamuna river was normal at its entry station at Palla in Delhi while beyond that it starts decreasing. After Wazirabad the DO level starts decreasing drastically and majority of times founds nil at Delhi downstream locations. It may be attributed due to discharge of wastewater from Shahadra drain and Hindon river (Mishra, 2010).

 

Petroleum and petroleum products and organochlorine pesticides are among the poorly degradable materials in water. Pesticides are persistent, accumulative and carcinogenic in nature. Synthetic organic chemicals i.e. plastics, solvents, detergents, paints, pesticides, food additives and pharmaceuticals produce objectionable taste and offensive smell to water, aquatic plants and fishes, even if they are present in low concentration.

 

2.  Agricultural discharges/nutrients: These include chiefly the chemicals used as fertilizers, pesticides (used in pest or disease control) and dissolved solids. These chemicals along with water are washed off lands through irrigation, rainfall, drainage etc. reaching into rivers, lakes, streams etc., where they disturb the natural ecosystem. Nitrate fertilizers used on soil enters our wells and ponds. Such water is thus very rich in nitrates. These nitrates are converted to nitrites by microbial flora of intestine. These nitrites then combine with the hemoglobin of blood to form methaemoglobin, which interferes with the oxygen carrying capacity of blood. The disease produced is called methaemoglobinaemia leads to damage to respiratory and vascular system, causing blue colouration of skin (blue baby disease) and even cancer. Water Groundwater in Ambala and Gurgaon districts and surface water supply in Hisar district of Haryana was found to be contaminated with isomers of HCH, endosulfan and metabolites of DDT (Kaushik et al. 2012). Irrigated agriculture, especially in arid areas, is always vulnerable to an accumulation of salts due to evapo-transpiration on the cropland itself.  The  salinity is  enhanced  by the  increased  evaporation  in  storage  reservoirs  that  typically accompany irrigation projects. In addition, irrigation drainage water may dissolve more salts from the soils with which it comes in contact, further increasing its salinity. As a result, irrigation drainage is always higher in salinity than the supply water and with every reuse, its salt concentration increases even more. 1500 mg/l total dissolved solids (TDS) can be tolerated by most crops with little loss of yield, but at concentration above 2100 mg/l water is generally unsuitable for irrigation except for most salt tolerant crops. Salinity problems are also having major impacts on irrigated lands in Iraq, Pakistan, India, Mexico, Argentina, Mali and North African countries. The collapse of ancient civilizations which once flourished in the Fertile Crescent in now what in new Iraq is often attributed to the demise of irrigated agriculture caused by accumulating salts. Fertilizers have an entirely different effect on water. The fertilizers salts that are often easily water soluble are mixed with ground and surface water by excessive precipitation. Among the most often used fertilizers, K+ and Ca2+ are largely insignificant since the concentrations that occur in surface and ground water are nontoxic and mostly ecologically harmless. By contrast, NO3-, NH4+, H2PO4- and HPO42- contribute to eutrophication of the water.

 

3. Inorganic Pollutants

 

Inorganic pollutants i.e. sediments and salts, deicing salts, and acid mine drainage causes surface water pollution. The natural processes of soil erosion give rise to sediments in water. Soil erosion gets accelerated 5‒10 times as a result of agricultural activities and 100 times due to construction activities (De and De, 2004). Deforestation, mining activities also cause soil erosion. Water naturally accumulates a variety of dissolved solids or salts, as it passes through soils and rocks, on its way to the sea. These salts typically include sodium, calcium, magnesium, potassium, chloride, sulfate and bicarbonates causes salinity. The more common measure of salinity is total dissolved solids (TDS) As a rough approximation, water can be considered to be fresh with TDS less than 1500 mg/l; brackish waters with TDS values up to 5000 mg/l; saline waters with concentrations above 5000 mg/l (Walker, 2014) and sea water contain 30,000–34,000 mg/l TDS.

 

NaCl (sodium chloride) is most usually used as a deicing salt for snowy and icy streets; even in high concentration it is nontoxic for most life forms. However, since NaCl is a highly active osmotic salt and it can burden the osmosis regulatory system of freshwater animals. Coal mines especially those which are abandoned, discharge substantial quantities of sulfuric acid (H2SO4) and also ferric hydroxide (Fe(OH)3) into local stream through seepage. The stream beds, contaminated with mine water are often coated with odd yellow deposits of amorphous semi-gelatinous Fe(OH)3. Sulfuric acid from acid mine water destroys aquatic life in water bodies. This water contains heavy metals which are harmful in many ways to aquatic life.

 

4.  Industrial Effluents: A wide variety of both inorganic and organic pollutants are present in effluents from breweries, tanneries, dying, textiles, paper and pulp mills, steel industries and mining operations. The effluents from industries contain many chemicals that are toxic to living organisms and causes water pollution. Industrial effluents contain variety of chemicals, dyes, salts, oil, grease, plastics, metallic wastes, suspended solids, phenols, toxins and heavy metals. Hot water as a waste contributes thermal pollution. Textile industries and tanneries impart colour due to synthetic dyes whereas paper industries waste water is on reddish tinge due to presence of lignin and tannin. The effluent from different industries contains heavy metals which can enter our food chains. For example during 1953‒60 in Japan more than 100 people lost their lives and many thousands were permanently paralyzed from eating mercury contaminated fishes, the disease is known as Minimata disease. In another case of cadmium toxicity/accumulation many people suffered from Itai‒Itai or Ouch–Ouch disease in which bones become fragile. Table 2 shows BOD5, and other pollutants from waste water from different types of industries.

Petrochemicals, bleach making, fertilizers, petroleum refineries, steel industries effluent contain cadmium. The waste water of paper, leather, textile, cement, ceramics, steel, fertilizer and petroleum industries is having chromium in it. Copper is present in paper, fertilizer, petroleum refineries, steel, non-ferrous metals, motor vehicles, air craft’s. Mercury and lead are present is paper, petro-chemicals, fertilizers, steel industries etc. Nickel and zinc are present in electroplating, paper, fertilizers, steel, petroleum refineries etc. Some heavy metals undergo microbial alkylation whereby they can enter into food chains. Methylation certainly occurs in arsenic and mercury. Under aerobic condition trimethyl arsenate is formed, whereas under anaerobic conditions dimethyl arsenate is formed. Organically compounded mercury is absorbed in the stomach, intestinal tract and through skin with a half of 70‒80 days. Cadmium can substitute for the zinc in enzymes with a zinc content (hrdroxylases). These enzymes become ineffectual in this process. The biological half life for cadmium is 10 years or more. Cadmium expels the zinc from certain enzymes and can also cause very painful bone deformation. Lead (Pb2+) can enter bones. In the bone marrow lead suppresses the synthesis of blood by inhibiting the enzyme 5-amino-levulin-acid dehydrate. Inorganic mercury compounds migrate into kidney cortex where they form chelates. They react with enzymes in the kidney canals and thus inhibit excretion.

 

Alkyl mercury and chromium (III) compounds have mutagenic and carcinogenic effect. Chromium compounds, particularly as Chromate (CrO42-), can readily enter cells, apparently because of their structural similarity to SO42- which can easily pass through the biomembranes. But as soon as reduction to Cr (III) occurs, the transfer through the membranes ceases. Heavy metals are highly persistent in the body because they are combines with specific proteins called metallothioneines. As long as they remain in this combines state the heavy metals are non toxic for the organism. Plants form phytochelates which will deposit in the cellulose cell walls, makes plant generally more resistant to heavy metals than humans or animals. Tanneries causing pollution of holy river Ganga in Kanpur (Hammer, 2007), dumping of treated and untreated sewage and industrial discharges causes pollution of 22 Km stretch of river Yamuna in Delhi, and pollution of Buddha Nullah river run through Ludhiana before draining into Sutlej River due to organic pollutants (Prashar, 1997) are few examples of river water pollution in India.

 

5. Radioactive materials: Naturally occurring radionuclide Tritium (emit beta particles) forms in the upper atmosphere and can be deposited onto surface waters via precipitation or snowfall. It can also seep into and accumulate in groundwater. Different human activities like ore processing, nuclear weapons testing, nuclear power plants, use of isotopes in various applications etc. are responsible for releasing different radioactive substances in to aquatic bodies and causes radioactive pollution. Mining and processing of ores to produce usable radioactive substances e.g. a typical uranium ore contains about 2-5 IBs of U3O3 per ton so that large amounts of ore are processed for extraction of uranium. Use of radioactive materials in nuclear weapons, use of radioactive materials in nuclear power plants and use of isotopes in medical, industrial and research applications are also responsible for radioactive constituents in drinking water. The radionuclide’s found in water include Ra-226 and K-40 originating from leaching of minerals; Sr-90, I-131, Ba-140, Cs-141, Kr-85, Co-60, Mn-54, Fe-55 and Pu-239 originates from reactors and uranium testing. Nuclear power plants generates liquid and gaseous wastes from waste fuel elements, fission products, low level radioactive liquid and waste heat. Sr-90 is a long lived component of radioactive fallout and is chemically similar to Ca and accompanies Ca in soil, plants, animals and finally into man in bones and teeth. The presence of Sr-90 in bones leads to disorders in blood cell formation and causes anemia or more serious orders.

 

Water withdrawal

 

Himalayan rivers have plenty of water in their upstream, however, they become water starved on entering the plains.

 

 

Ground water pollution

 

Ground water becomes contaminated from natural as well as from different types of human activities.

 

Natural sources

 

The naturally present substances such as arsenic, chlorides, fluorides, iron, manganese, sulphates or radionuclides in rocks or soil can become dissolved in ground water. In addition other naturally occurring substances such as decaying of organic matter can move in the ground water depending upon the local conditions. The unacceptable concentration of these substances in groundwater make it unfit for the use of drinking or other domestic purpose until these impurities are not removed. Some substances if consumed in excess quantities may pose health threat and the others may produce an undesirable odor, taste or colour. The Committee on Estimates observed that 68 districts in 10 Indian states namely Haryana, Punjab, Uttar Pradesh, Bihar, Jharkhand, Chhattisgarh, West Bengal, Assam, Manipur and Karnataka (Table 3) are affected by high arsenic contamination in groundwater (Committee on Estimates 2014‒2015).

 

Anthropogenic activities

 

Residential, municipal, commercial, industrial and agricultural activities can affect ground water quality (Table 4). Contaminants can reach up to ground water from the activities on the land surface such as release or spills from stored industrial wastes, septic system or leaking underground petroleum storage system etc.

 

Septic System: Pit latrines and septic tanks are common modes of onsite sanitation used in India causing groundwater contamination. The chemical contaminants and pathogenic bacteria released from these onsite sanitation systems are in filtered into nearby groundwater sources through soil media and causing the threat. This threat is more severe in dense habitation where both onsite sanitation and drinking water resources are spaced very close (Shivendra and Ramraju, 2015). The unscientific disposal of human and animal wastes is found to be the main anthropogenic activity that has led to the contamination of ground water with microorganisms, nitrates, potassium etc. Seepage of detergents containing waste water into ground and into refuse deposit may also mobilize toxic materials and thus further endanger the ground water. Contamination of drinking water sources by sewage can occur from raw sewage overflow, septic tanks, leaking sewer lines, land application of sludge and partially treated waste water. Sewage itself is a complex mixture and can contain many types of contaminants. The greatest threats posed to water resources arise from contamination by bacteria, nitrates, metals, trace quantities of toxic materials, and salts. Seepage overflow into drinking water sources can cause disease from the ingestion of microorganisms such as E coli, Giardia, Cryptosporidium, Hepatitis A, and helminths. Leachate from onsite sanitation system is the one the source of ground water pollution (ARGOSS, 2001). Increased concentration of nitrate and bacteria in groundwater near septic tank system in India was reported (Pujari et al. 2012). Increased concentration of total and fecal coliform during monsoon period in saturated condition of sandy soils and less in clay soils was investigated by Banerjee (2011) in West Bengal in India. On the other hand Kaushik et al (2000) reported that ground water pollution was significantly higher in those areas where there was quantitatively large dumping of solid wastes.

 

Improper Disposal of Hazardous Waste and landfill:

 

The large number of municipal solid waste (MSW) landfills and the many hazardous materials which they contain pose a serious threat to both surrounding environment and human populations. Once waste is deposited at the landfill, pollution can arise from the percolation of leachate to the porous ground surface. Contamination of groundwater by such leachate renders it and the associated aquifer unreliable for domestic water supply and other uses. There are atleast 320 sites across India that host hazardous waste which affects directly or indirectly about 2 lakh people. These are called orphan sites because industries and municipal agencies dumped hazardous waste at such sites and abandoned them. Most of the sites are located in the states of Uttar Pradesh, West Bengal, Odisha, Delhi, Karnataka, Gujarat, Jharkhand, Tamil Nadu, Kerala, Andhra Pradesh/Telangana and Punjab. Of the identified sites and pollutants, chromium is found in the largest number of places, followed by lead, cadmium, mercury and pesticides. In most sites, there is more than one contaminant (Hindustan Times, 2017).

 

Release and spills of stored chemicals and petroleum product

 

The petroleum products and other chemical substances are commonly stored in underground and aboveground storage tanks. The underground ground storage tank develop a leak as the tank ages and corrodes, its contents can migrate through the soil and reaches the ground water. Abandoned underground tanks pose another serious threat because of their unknown location. Above ground storage tanks can also be problematic if a spill or leak occurs and adequate barriers are not in place.

 

Improper constructed and abandoned wells

 

Improper constructed well can result in ground water contamination when contaminated surface or ground water is introduced in the well. The improper constructed well can act as conduit through which contaminants can reach to the aquifer. It has also been observed that some people use abandoned well to dispose of waste such as used motor oil and contaminate the drinking water supply.

 

Poorly constructed irrigation wells

 

Pesticide and fertilizers applied in immediate vicinity of the wells on agriculture land can allow the contaminants to enter into the ground water (Parashar, 2016). According to the Ministry of Chemicals and Fertilizers (Indian Fertilizer Scenario 2014), the use of nitrogenous fertilizers in the country has augmented by more than 50 % since 2000. India is the second highest consumer of nitrogen in the world after China. According to the Food and Agriculture Organisation (FAO), India’s annual consumption of nitrogen is 16.48 million tones. The increasing rate of nitrogen fertilizers have directly or indirectly causing nitrate pollution and led to an imbalance to the environment and degrade the groundwater quality.

 

Mining Activity

 

Active and abandoned mines contribute to ground water pollution. The leaching of soluble minerals takes places via precipitation from mine waste to ground water below and this leaching waste often contain metals, acid, mineral and sulphides. A study carried out in 2008 Sukinda Valley, Orissa is known for its chromite ore deposits. The chromium mining is being carried out in this area since 1950. The leaching contaminants from the ore material kept in the open ground or from the wastages or degraded ore material produced during the mining processes has contaminated the groundwater in the study area. There is also a high possibility that the contaminants will move to the aquifer system from the seepage of bottom floor of the mining quarry. The groundwater samples collected from different sites of study area has nearly neutral to mildly alkaline in pH (6.1‒7.6), low to moderate TDS (50‒ 507 mg/l), high TSS (4‒64 mg/l), Cu (0.01‒1.8 mg/l) and Cr (VI) (0.01‒0.45 mg/l).

 

Pathways of ground water pollution

 

Depending upon the physical, chemical and biological properties of the contaminant that has been released into the environment may move within an aquifer in a similar manner as ground water moves, however some contaminant do not always follow the ground water flow because of their physical and chemical properties. For example, both water and certain type of contaminants can along with flow of ground water. Permeable soils likely to transmit water and certain type of contaminants with relative ease in aquifers. The contaminants and ground water can move quickly through the fractured rocks, through animal’s burrows, abandoned wells, macrospores‒root system and other system of holes and cracks. The potential of contamination increases in the areas surrounding pumping wells because the water from the zone of contribution is drawn into the well from the surrounding aquifer. Some drinking water wells draw water from nearby streams lakes and river. Some wells rely on artificial recharge and often using water from irrigation, storm runoff, industrial process or treated sewage to increase the amount of water infiltrating an aquifer. This practice has caused increased concentration of metals, nitrates, microbes or synthetic chemicals in the water. Under certain circumstances the contaminants enters from one aquifer to one being pumped and do so associated contaminants. This phenomenon is known as interaquifer leakage.

 

Effects of water pollution

 

According to World Health Organization (WHO 2007), lack of water, sanitation, and hygiene results in the loss of 0.4 million lives annually in India. The country loses 90 million days a year due to water borne diseases with production losses and treatment costs worth Rs 6 billion (McKenzie and Ray, 2004). In addition, 10 million people are vulnerable to cancers from excessive arsenic and another more than 65 million people are facing risk of fluorosis, now endemic in 17‒20 States (Khurana and Sen, 2007; Maria, 2003; Position paper, 2011).

 

Control of water pollution

 

Some of the strategies to control water pollution are:

 

1.  Discharge of domestic and industrial waste water after proper treatment.

 

2.  Implement strict laws

 

3.  Maintain drinking water quality

 

4.  Create public awareness.

 

Conclusion

 

To improve the water quality of lakes and rivers, there is an urgent need to increase the capacities of sewage treatment plants and their optimum utilization. Our country should give stress on developing a 100 % treatment capacity up to the secondary level of treatment. Treated water can be used in industries, irrigation purposes and for recharging replenishing groundwater. Industries should be encouraged to re-use treated municipal wastewater. Public awareness should be created among users and public for encouraging their effective participation in water management practices and developing ethical concepts for making efficient use of water resources.

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