In this speech we will discuss about:- 1. Speech on the Introduction to Water Pollution 2. Speech on the Types of Water Pollution 3. Categories 4. Speech on the Sources of Water Pollution 5. Speech on the Causes of Water Pollution 6. Biological Oxygen Demand (BOD) 7. Effect of Water Quality on Human Health 8. Speech on the Effects of Water Pollution 9. Water Quality & Pollution 10. Speech on the Devices used for Pollution Control 11. Speech on How to Stop 12. Methods. Also learn about:
- Speech # Introduction to Water Pollution
- Speech # Types of Water Pollution
- Speech # Categories of Water Pollution
- Speech # Sources of Water Pollution
- Speech # Causes of Water Pollution
- Speech # Biological Oxygen Demand (BOD)
- Speech # Effect of Water Quality on Human Health
- Speech # Effects of Water Pollution
- Speech # Water Quality & Pollution
- Speech # Specific Devices for Water Pollution Control
- Speech # How to Stop Water Pollution?
- Speech # Methods for Minimizing the Problem of Water Pollution
Speech # 1. Introduction to Water Pollution:
Next to air, water is the most important substance for the existence of life on earth. Water accounts for about 70% of the mass total of our body. It is an essential constituent of all flora and fauna and forms about 75% of the matter of the earth’s crust. Water is distributed in nature in different forms, such as rainwater, river water, spring water and mineral water. Rainwater is the purest form of naturally occurring water. The sum total of all the available water on the surface of earth is called hydrosphere.
Water is an excellent solvent because:
(a) It has high dielectric constant,
(b) It is hydrogen bonded, and
(c) It is polar a molecule and has dipole moment.
Much of the heat generated by metabolism in our bodies is removed by evaporation of water through the pores of the skin. Water, the most abundant and wonderful natural resource, has become a precious commodity today and its quality is threatened by numerous sources of pollution.
The term pollution is derived from the Latin word pollutus — pol (before) + lutus (wash), i.e., before washing. Water contains impurities and, hence, the term pollution is applied to indicate an act of contamination or making foul the natural water bodies such as rivers, wells, lakes, streams, seas.
Water is the soul of nature; its pollution will perish the whole world.
Water pollution may be defined in a number of ways:
1. Undesirable changes occurring in water, which adversely affect the life activities of human and domesticated species.
2. Alteration in physical, chemical and biological characteristics of water which may cause harmful effects on human and aquatic biota.
3. Addition of excess of undesirable substances to water that makes it harmful to man, animal and aquatic life, or otherwise causes significant departure from the normal activities of various living communities in or around water.
4. Any adverse change in conditions or composition of the water so that it becomes less suitable for the purpose for which it would be suitable in its natural state.
5. In reality, the term water pollution refers to any type of aquatic contamination between two extremes:
(i) A highly enriched, over-productive biotic community such as a river or a lake with nutrients from sewage or fertilizer (cultural eutrophication), or
(ii) A body of water poisoned by toxic chemicals which eliminate living organisms or even exclude all forms of life.
Surface water pollution- Surface waters are the natural water resources of the Earth.
They are found on the exterior of the Earth’s crust and include:
Oxygen Depleting Pollution:
Microorganisms that live in water feed on biodegradable substances. When too much biodegradable material is added to water, the number of microorganisms increase and use up the available oxygen. This is called oxygen depletion. When oxygen levels in the water are depleted, relatively harmless aerobic microorganisms die and anaerobic microorganisms begin to thrive. Some anaerobic microorganisms are harmful to people, animals and the environment, as they produce harmful toxins such as ammonia and sulfides.
A lot of the Earth’s water is found underground in soil or under rock structures called aquifers. Humans often use aquifers as a means to obtain drinking water, and build wells to access it. When this water becomes polluted it is called groundwater pollution. Groundwater pollution is often caused by pesticide contamination from the soil; this can infect our drinking water and cause huge problems.
Nutrients are essential for plant growth and development. Many nutrients are found in wastewater and fertilizers, and these can cause excess weed and algae growth if large concentrations end up in water.
(i) This can contaminate drinking water and clog filters.
(ii) This can be damaging to other aquatic organisms as the algae use up the oxygen in the water, leaving none for the surrounding marine life.
Microbiological water pollution is usually a natural form of water pollution caused by microorganisms.
Many types of microorganisms live in water and cause fish, land animals and humans to become ill.
(i) Bacteria Viruses
Serious diseases such as cholera come from microorganisms that live in water. These diseases usually affect the health of people in poorer countries, as they do not have the facilities to treat polluted water.
Suspended Matter Pollution:
Some pollutants do not dissolve in water as their molecules are too big to mix between the water molecules. This material is called particulate matter and can often be a cause of water pollution.
(i) The suspended particles eventually settle and cause thick silt at the bottom. This is harmful to marine life that lives on the floor of rivers or lakes.
(ii) Biodegradable substances are often suspended in water and can cause problems by increasing the amount of anaerobic microorganisms present.
(iii) Toxic chemicals suspended in water can be harmful to the development and survival of aquatic life.
Industrial and agricultural work involves the use of many different chemicals that can run-off into water and pollute it.
(i) Metals and solvents from industrial work can pollute rivers and lakes. These are poisonous to many forms of aquatic life and may slow their development, make them infertile or even result in death.
(ii) Pesticides are used in farming to control weeds, insects and fungi. Run-offs of these pesticides can cause water pollution and poison aquatic life. Subsequently, birds, humans and other animals may be poisoned if they eat infected fish.
(iii) Petroleum is another form of chemical pollutant that usually contaminates water through oil spills when a ship ruptures. Oil spills usually have only a localized effect on wildlife but can spread for miles. The oil can cause the death of many fish and stick to the feathers of seabirds causing them to lose the ability to fly.
There may be four categories of water pollution:
2. Chemical Pollution of Water
3. Biological Pollution of Water
4. Physiological Pollution of Water
Physical pollution of water refers to the changes in physical properties of water viz., colour, odour, taste, density, thermal properties, viscosity, turbidity etc.
The chemical pollution of water causes changes in acidity, alkalinity i.e. pH, dissolved oxygen (DO) and other gases in water. It may be caused either by inorganic or organic pollutants or both. The organic as well as inorganic pollutants may be biodegradable or non-biodegradable type.
(i) Biodegradable Pollutants:
Biodegradability by definition is the destruction of chemical pollutants by the action of living organism. The degradation of pollutants can be accomplished by any living organisms but the microbes (bacteria, fungi and algae) play extremely important role. This is because of their catabolic versatility, species diversity and metabolic rate per unit weight. Reactions include oxidation, reduction, hydrolysis and often various types of structural rearrangement.
The feasibility of occurrence of these processes is determined by the molecular structure and concentration of the pollutant, the nature of microbes in existence and the prevailing environmental conditions. In nutshell, the pollutants that can be rapidly decomposed by the natural living agents (by the action of microbes) are called biodegradable pollutants.
For a chemical pollutant to be biodegraded efficiently, the following set of criteria must be met:
a. At least one microbial species capable of metabolizing the chemical pollutant in question should be present in the media.
b. Contact between the organisms and the chemical molecules should occur.
c. The chemical pollutants must be capable of inducing the enzymes needed for its decomposition.
d. Favourable environmental conditions (optimum pH, temperature etc.) for the microbes to proliferate and for their enzymes to operate should exist.
For several chemical pollutants, these conditions are known to be met satisfactorily. In other words, there do exist various species of microbes that degrade several of the organic pollutants in the environment under normal conditions.
a. Proteins from domestic sewage, waste from creameries, canneries and slaughter houses.
b. Fats from sewage, soap production, food processing and wool processing.
c. Carbohydrates, (sugar, starch) etc. from sewage, textile mills and paper mills.
d. Polymers, resins, coal, oil and various other organic substances found in domestic and industrial wastes and those synthetic compounds which are non-toxic to some microbes.
It is important to mention here that highly branched organic pollutants are much resistant to biodegradation because increased substitution hinders oxidation, the process by which alkyl chains are broken down microbially. Other aspects of pollutants, viz., chemical structure, play key role in biodegradation; for example – position of the phenyl group, length of the alkyl chain and the presence of cyclic groups.
The excretory products of endothermic (warm-blooded) bacterial population in water are main cause of biological pollution. Biological pollution is also brought about by algae, diatoms like protozoans, rotifers, crustaceans, plant toxins, and viruses. Contaminated water supplies frequently produce infection of intestinal tract (like dysentery, cholera, typhoid and gastroenteritis), polio and infectious hepatitis.
Several chemical agents such as chlorine, SO2, H2S, ketones, phenols, amines, mercaptans and hydroxy benzene are responsible for physiological pollution of water. Chlorination of water usually converts phenol to ortho or para chlorophenol which tastes like medicine and produces offensive odours.
Speech # 4. Sources of Water Pollution:
Four main sources of water pollution are:
1. Domestic effluents,
2. Industrial effluents,
3. Surface run off and
4. Waste heat.
1. Domestic Effluents:
This includes human and animal excreta, detergent, organic matter in the form of food residue and large amount of bacteria.
This has three types of impurities suspended solid (soil, sand and clay), colloidal particle (inorganic and organic large size compound, fiber, cloth, paper, etc.) and dissolved solids (organic compounds, toxic metal ions, inorganic nutrients). These three impurities together form about 0.1% of domestic sewage.
Domestic sewage contains biodegradable matter and can be decomposed by aerobic bacteria and micro-organisms. Biochemical Oxygen Demand (BOD) is the amount of oxygen required by microorganisms in milligrams in five days to completely decompose the organic matter present in one litre of polluted water at 20°C. Higher the amount of oxygen used greater is the amount of pollutants.
This means higher the amount of oxygen consumed, greater is the degree of organic pollutants. The input of domestic sewage containing high amounts of biodegradable organic matter increases the BOD of water body. As these microorganisms use Dissolved Oxygen (DO) so the amount of BOD is inverse to DO.
This means that in highly polluted water body there is very high BOD and low DO. The lowering of DO causes death of large number of aquatic organisms and disturbs the aquatic food chain. The amount of oxygen required to oxidise all the pollutants in 1 litre of water at 20°C in 5 days is called Chemical Oxygen Demand (COD).
2. Industrial Effluents:
Industrial discharge like alkalis, acids and heavy metals, inorganic and organic pollutants. These are discharged in water bodies like ponds, lakes and rivers. These pollute both land and water. A few of them can be carcinogenic. Heavy metals and some other pollutants destroy the aquatic life.
3. Run off Water:
Run off water brings along with it insecticides, pesticides, fertilisers, manure, etc. Some of these are non-biodegradable. Excess of fertilisers increases the amount of nitrates in the water bodies. This causes increase in growth of algae and the process is known as algal bloom or eutrophication. Due to this, the oxygen content of water goes down. This leads to suffocation and death of aquatic life. Water becomes unfit for drinking and even for industrial purpose. Accumulation of pesticides like DDT leads to bio magnification.
4. Effects of Water Pollution:
As the pesticides, fertilisers and insecticides are added, it increases the amount of nutrients which leads to algal bloom, further leading to destruction of aquatic life. Death of aquatic life causes foul smell in water bodies. Same thing happens when detergents are added.
As we discharge domestic sewage in water bodies it increases the amount of decomposers. Typhoid, cholera, jaundice, hepatitis and dysentery are a few diseases caused by polluted water. Addition of arsenic, lead and mercury (neurotoxin) causes black foot disease. Mercury causes memory loss and vision disorder, whereas arsenic causes lung and skin cancer and diarrhoea. Water contaminated by cadmium causes Itai-itai which occurred in Japan. Nitrates cause blue babies. Fluorides cause skeletal fluorosis or knock knee disease.
1. Domestic Sewage – The city sewage is released into the river. Domestic sewage consists of human faeces, urine and the dirty used-up water in houses. It contains a large number of pathogenic bacteria and virus.
2. Industrial Effluents – All industrial plants produce some organic and inorganic chemical wastes. Those non-usable chemicals are dumped in water as a means of getting rid of them. The industrial wastes include heavy metals (Hg, Cu, lead, zinc, etc.), detergents, petroleum, acids, alkalis, phenols, carbonates, alcohol, cyanides, arsenic, chlorine, etc.
3. Thermal Pollution – Many industries use water for cooling. The resultant warm water is discharged into rivers. This brings about thermal pollution.
4. Fertilizers – The fertilizers used for crops are washed into ponds and rivers.
5. Pesticides – Pesticides are used to control pests in fields and houses. They include DDT, BHC, endrin, etc.
6. Radioactive Wastes – Liquid radioactive wastes are released into the sea around nuclear installations. The oceanic currents carry the radioactive contaminants everywhere.
7. Oil Pollution – Oil is a source of pollution in sea- water. Oil pollution is due to ship accidents, loading and discharging of oil at the harbour, oil refineries and off-shore oil production.
8. Retting – The process of decaying coconut husk to get fibre for making coir is called retting. Retting releases H2S. It makes water polluted.
BOD is not a pollutant but an indicator of water quality (pollution index of aquatic body). It has been a standardized measurement of the amount of O2 that would be required by microbes to cause the decomposition of certain organic and inorganic matter in the water. The measurement is done under standardized condition (at 20°C and 5 days to allow the decomposition to take place).
The result is called the 5 day BOD and is expressed in milligrams of O2 per liter of water. It measures no particular substance but a family of any substance that microbes can consume (using O2 as they do).
The BOD test as a measure of pollution degree in water was first adopted in 1912 by “The Royal Commission on Sewage Disposal”.
One of the most serious effects of human and industrial wastes (or effluents) is to increase the BOD of natural water supplies. Aerobic bacteria use O2 to decompose the complex organic compounds in sewage to simpler and generally unobjectionable species such as CO2, NO3, ions and SO4 ions.
This process reduces the amount of DO in water, sometimes to the point where animal life is difficult to survive. If the oxygen content drops too low, anaerobic bacteria take over the decomposition process, forming rather noxious pollutants such as CH4, NH3 and H2S.
The BOD of polluted water can be determined by measuring the amount of O2 consumed by a sample of known volume. The water sample is first diluted with air-saturated distilled water to ensure an excess of O2. The concentration of DO in the dilute sample is immediately determined, and again after a period of 5 days.
From the decrease in concentration, BOD can be calculated:
Calculate the BOD of a water sample which contains one gram of urea for every 100 liters of water. The reaction between urea and O2 is –
NH2CONH2 + 4O2 → CO2 + 2NO3– + 2H+ + HOH
Balanced equation reveals that 4 molecules of O2, are required to react with one molecule of carbamide, i.e. urea. One molecule of O2 weighs 32.0 gm and one mole of NH2CONH2 (urea) weighs 60 gm. Now we have
BOD of given sample = 21.3 mg/l or 21.3 ppm.
A BOD test normally measures the amount of O2 used up over a 5 day period by aerobic decomposers in certain volume of effluent at 20°C, the result being expressed in ppm. Thus a 100 ppm BOD means that 100 mg of O2 are consumed by one liter of the test sample (e.g., effluent, sewage, water) over a 5-day period at 20°C. Increased BOD lowers the DO content in water causing the suffocation and death of aquatic flora and fauna.
Limitations of BOD Test:
i. Before BOD test, the pre-treatment of sewage is necessary if it also contains toxic wastes.
ii. The test is applicable only in the case of biodegradable organic matter.
iii. A high concentration of the active bacteria is necessary to be present in the sample of sewage.
iv. Before applying BOD test, the effects of nitrifying organisms are to be reduced.
v. There is no validity of the test after the organic matter present in the sample of sewage is utilized or exhausted.
vi. The time required for the test is long as well as arbitrary.
(i) Used as a measure for determining the strength of sewage.
(ii) Aids in finding out the amount of clear water needed for the successful disposal of sewage by dilution.
(iii) Gives information of polluting power of sewage or its nuisance value.
(iv) Gives an idea of the load of organic matter on the sewage treatment plants.
Chemical oxygen demand (COD) may be defined as the amount of O2 required by organic matter in a sample of water for its oxidation by a strong chemical oxidant, and is expressed as ppm of oxygen taken from a solution of acidic K2Cr2O7 in two hours at high temperature.
As BOD value approximates the amount of oxidizable organic matter, it is, therefore, used as a measure of degree of water pollution and waste strength. But COD value has been a poor measure of strength of organic matter as O2 also gets consumed in the oxidation of inorganic matter such as nitrate, sulphates, reduced metal ions and also that some organic materials like Benzene, Pyridine and few other cyclic organic compounds do not get oxidized by this test. COD of sewage is higher than its BOD, because more compounds can be oxidized than can be biologically degraded.
Types of microbes, pH, presence of toxins, some reduced mineral matter and nitrification process have been the important factors that influence the BOD test. But presence of toxins and other such unfavourable conditions for the growth of microbes are not able to affect COD values. The limiting value of COD has been specified to be 250 ppm. The inorganic compounds should be removed before COD test.
Speech # 7. Effect of Water Quality on Human Health:
The effect of toxic contaminants (metals, organic compounds, microorganisms) on human health can be classified as either acute or chronic. The reaction to a substance causing serious illness or death in an individual within 48 hours after exposure is considered acute toxicity.
On the other hand, chronic toxicity has a long-term effect on health due to frequent exposure to small amounts of a toxic substance. Chronic reactions to chemicals are difficult to study and our knowledge of the chronic toxic effects of nearly all chemicals is very poor.
Although high nitrate levels are usually due to human activities they may be found naturally in ground water. They come from the breakdown of nitrogen compounds in the soil. The problem of nitrate contamination deserves more scrutiny in daily life. Nitrates are present under its basic form (K and Ca), aluminium, iron, and under certain other heavy metal forms. Nitrate is readily water-soluble, easily permeates the ground and contaminates groundwater.
A variety of chemicals, including nitrate, can pass through the soil and potentially contaminate ground water. Nitrate comes from nitrogen, a plant nutrient supplied by inorganic fertilizer and animal manure. Additionally, airborne nitrogen compounds given off by industry and automobiles are deposited on the land in precipitation and dry particles. Other non-agricultural sources of nitrate include fertilizers, septic systems, and domestic animals in residential areas.
Beneath agricultural lands, nitrate is the primary form of nitrogen. It is soluble in water and can easily pass through soil to the ground-water table. Nitrate can persist in ground water for decades and accumulate to high levels as more nitrogen is applied to the land surface every year. Nitrogen inputs comprise the following two factors – ‘loadings’ from agricultural and non-agricultural sources; and ‘population density,’ a variable used to indicate additional non-agricultural sources of nitrogen in urban areas.
Nitrogen loadings are contributed by inorganic fertilizers, animal manure, and atmospheric deposition of airborne nitrogen compounds. Population density represents nitrogen sources such as residential fertilizers, septic systems, and domestic animal waste in urban areas.
Nitrates contamination of the world’s underground water supply poses as a potentially serious health hazard to the human inhabitants on earth. High nitrate levels found in well water have been proven to be the cause for numerous health conditions across the globe. If we intend to provide for the future survival of man, and life on planet earth, we must take action now to assure the quality of one of our most precious resources, our underground water supply.
The maximum allowable amount of nitrate as per ICMR standards in water is 45 mg 1–1. The transformation reaction of nitrate into nitrite in the human body by bacteria leads to the rapid combination of nitrite with blood.
Nature and humans are the main causes of nitrate contamination with the following characteristics:
1. The main source of nitrate resides in the agricultural fertilizers, which, if unabsorbed by the vegetation, remains on the ground surface, and gradually infiltrates the groundwater.
2. The natural sources of nitrate are excessive rainfall and the oxidation of organic compounds, including daily human wastes.
3. Nitrates are found in human and animal wastes. Septic tanks can cause bacterial and nitrate pollution. Both septic systems and animal manures must be carefully managed to prevent pollution. Sanitary landfills and garbage dumps are other sources.
Studies indicate that nitrate levels that exceed 45 ppm can cause a condition known as methaemoglobinemia, or Blue Baby Syndrome in infants.
Symptoms of methaemoglobinemia are anorexic appearance, shortness of breath, nausea, vomiting, diarrhoea, lethargy, and in more extreme cases, loss of consciousness and even death. When nitrate is ingested it is converted into another chemical form, i.e., nitrite.
Nitrite then reacts with haemoglobin, the protein responsible for transporting oxygen in the body, converting them to methaemoglobin, a form that is incapable of carrying oxygen. As a result, the victim suffers from oxygen deprivation, or more commonly stated, the individual slowly suffocates.
Although, methaemoglobinemia is the most immediate life-threatening effect of nitrate exposure, there are a number of equally serious long-term, chronic impacts. In numerous studies, exposure to high levels of nitrate in drinking water has been linked to a variety of effects ranging from hypertrophy (enlargement of the thyroid) to different types of cancer, birth defects, and even hypertension.
Since 1976 there have been at least 8 different epidemiological studies conducted in 11 different countries which show a definite relationship between increasing rates of stomach cancer and increasing nitrate intake. Studies also indicate that presence of high quantity of nitrate causes cyanosis among infants and much higher quantities may even lead to gastric carcinoma. Nitrates are converted to nitrites, which are further converted to nitrosamines, which are believed to be responsible for malignant transformation of gastric mucosa.
These chemical conversions take place readily in the presence of certain bacteria, which can be found in the gastro-intestinal tract of individuals consuming improperly cooked food or stale food. This fact probably explains the higher incidence in lower social economic classes.
Groundwater contamination by nitrates, which may be due to organic pollution, have led to high incidence of non-Hodgkin’s lymphoma and increased risk of insulin-dependent diabetes mellitus (IDDM) in children below 18 years of age.
The effects of water pollution are varied. They include poisonous drinking water, poisonous food animals (due to these organisms having bio-accumulated toxins from the environment over their life spans), unbalanced river and lake ecosystems that can no longer support full biological diversity, deforestation from acid rain, and many other effects. These effects are, of course, specific to the various contaminants.
Surface and ground waters are subject to pollution from different sources. The major water pollution is caused by the discharge of untreated waste waters into rivers, lakes and reservoirs. In India, for example, about 70 per cent of total surface water is polluted.
Water quality reflects the composition of water as affected by natural processes and human activities. Pollution is ‘an undesirable change in the physical, chemical or biological characteristics of our air, land and water’ that may affect human life or that of other species. Thus, pollution of water, be it surface water in rivers, reservoirs, lakes and ponds or subsurface or ground water, arises due to natural phenomena and human activities.
The question of water quality is a serious problem. This applies to surface water as well as groundwater. The sources of water pollution are from industrial effluents, poorly treated sewage and runoff of agro-chemicals combined with unsatisfactory household and community sanitary conditions.
Among these, agriculture makes a crucial contribution to the pollution of ground and surface water by fertilizers and pesticides. As consequence of leaching, nitrate and phosphate concentrations in ground water have been rising constantly over past decades.
Nitrogen in streams and rivers lead to eutrophication, which is especially aggravating the ecosystem. Rising nitrate concentration in ground water as a result of agricultural practice severely affect the water supply system, where significant portion of the drinking water is covered by ground water.
They are polluted by toxic substances such as chlorinated hydrocarbons and pesticides, microbial pollution and as the main pollutant-excessive nitrate concentrations. Another consequence due to over-exploitation and abstraction of groundwater is the deterioration in water quality having increased salinity. Ground water contamination and poor quality have become a severe environmental risk not only in the developed but also in the developing countries all over the world.
This demands an increased awakening among public about groundwater quality as well as the high interest of the governmental authorities and the scientific community in protecting and remedying ground water resources. It is not only agricultural practice, with its application of manure and fertilizer that is responsible for nitrate leaching from the soil into the ground but also airborne depositions. Besides the well-known ‘acid rain’ the public does not yet realize that there is a large amount of nitrogen deposition which is causing severe problems especially in forested areas.
Ninety-five per cent of all fresh water on earth is ground water. Ground water is found in natural rock formations. These formations, called aquifers, are a vital natural resources with many uses. It is endangered by waste water infiltrating into the sub-soil from leaky sewers. Another problem is a result of the traditional drainage system that collects rain water from roofs, streets and other places together with waste water from households and industry in one single system of canals.
In the event of heavy rainfall, the total amount of water normally exceeds the capacity of the sewage plant and has to be discharged directly into streams and rivers. This combined sewage overflow from sewers after rainfall is one main cause of the chemical and microbial pollution of surface water. Due to the ingress of saline water from coastal regions and polluted water in other areas, water has become unusable.
Sources of water pollutants are broadly grouped into two—those arising from point sources and those from non-point sources. Point sources include sanitary landfills, hazardous waste disposal facilities and high level radioactive waste repositories. Non point sources include urban run-off waste from sewage, and infiltration contaminated by agricultural chemicals like fertilizers and pesticide including agricultural wastes.
Perhaps the largest rational example of pesticide contamination and human health is that of the Aral Sea region. UNEP (1993) linked the effects of pesticides to “the level of oncological (cancer), pulmonary and haematological morbidity, as well as on inborn deformities……… and immune system deficiencies”.
Human health effects are caused by:
i. Skin contact – Handling of pesticide products.
ii. Inhalation – Breathing of dust or spray.
iii. Ingestion – Pesticides consumed as a contaminant on/in food or in water.
Degradation of water quality by pesticide run-off has two principal human health effects. The first is the consumption of fish and shellfish that are contaminated by pesticides; this can be a particular problem for subsistence fish economies that lie downstream of major agricultural areas. The second is the direct consumption of pesticide-contaminated water. Many health and environmental protection agencies have established acceptable daily intake (ADI) values which indicate the maximum allowable daily ingestion over a person’s lifetime without appreciable risk to the individual.
Pesticides are induced in a broad range of organic micro-pollutants that have ecological effects. Different categories of pesticides have different types of effects on living organisms, therefore generalization is difficult. Although terrestrial effects by pesticides do occur, the principal pathway that causes ecological impacts is that of water contaminated by pesticide run-off.
The two principal mechanisms are:
This is the movement of a chemical from the surrounding medium into an organism. The primary ‘sink’ for some pesticides is fatty tissue (lipids). Some pesticides such as DDT, are ‘lipophilic’, meaning that they are soluble in, and accumulate in, fatty tissue such as edible fish tissue and human fatty tissue. Other pesticides such as glyphosate are metabolized and excreted.
The term describes the increasing concentration of a chemical as food energy is transformed within the food chain. As smaller organisms are eaten by larger organisms, the concentration of pesticides and other chemicals are increasingly magnified in tissue and other organs. Very high concentrations can be observed in top predators, including man.
The ecological effects of pesticides (and other organic contaminants) are varied and are often inter-related. Effects at the organism or ecological level are usually considered to be an early warning indicator of potential human health effects. The major types of effects are listed below and will vary depending on the organism under investigation and the type of pesticide.
Different pesticides have markedly different effects on aquatic life, which makes generalization very difficult. The important point is that many of these effects are chronic (not lethal) are often not noticed by casual observers, yet have impacts on the entire food chain.
i. Death of the organism,
ii. Cancers, tumors and lesions on fish and animals,
iii. Reproductive inhibition or failure,
iv. Suppression of immune system,
v. Disruption of endocrine (hormonal) system,
vi. Cellular and DNA damage,
vii. Teratogenic effects (physical deformities such as hooked beaks on birds),
viii. Poor fish health marked by low red to white blood cell ratio, excessive slime on fish scales and gills, etc.
ix. Integrational effects (effects are not apparent until subsequent generations of the organisms), and
x. Other physiological effects such as egg shell-thinning.
These effects are not necessarily caused solely by exposure to pesticides or other organic contaminants, but may be associated with a combination of environmental stresses such as eutrophication and pathogens. These associated stresses need not be large to have a synergistic effect with organic micro-pollutants.
According to the American College Dictionary, pollution is defined as – to make foul or unclean; dirty. Water pollution occurs when a body of water is adversely affected due to the addition of large amounts of materials to the water. When it is unfit for its intended use, water is considered polluted. Two types of water pollutants exist; point source and non-point source – Point sources of pollution occur when harmful substances are emitted directly into a body of water.
The Exxon Valdez oil spill best illustrates a point source water pollution. A non-point source delivers pollutants indirectly through environmental changes. An example of this type of water pollution is when fertilizer from a field is carried into a stream by rain, in the form of run-off which in turn affects aquatic life.
The technology exists for point sources of pollution to be monitored and regulated, although political factors may complicate matters. Non-point sources are much more difficult to control. Pollution arising from non-point sources accounts for a majority of the contaminants in streams and lakes.
When toxic substances enter lakes, streams, rivers, oceans and other water bodies, they get dissolved or lie suspended in water or get deposited on the bed. This results in the pollution of water whereby the quality of the water deteriorates affecting aquatic ecosystems. Pollutants can also seep down and affect the ground water deposits.
Water pollution has many sources. The most polluting of them are the city sewage and industrial waste discharged into the rivers. The facilities to treat waste water are not adequate in any city in India. Presently, only about 10% of the waste water generated is treated; the rest is discharged as it is into our water bodies.
Due to this, pollutants enter groundwater, rivers and other water bodies. Such water, which ultimately ends up in our households, is often highly contaminated and carries disease-causing microbes. Agricultural run-off, or the water from fields that drains into rivers, is another major water pollutant as it contains fertilizers and pesticides.
Domestic sewage refers to waste water that is discarded from households. Also referred to as sanitary sewage, such water contains a wide-variety of dissolved and suspended impurities. It amounts to a very small fraction of the sewage by weight. But it is large by volume and contains impurities such as organic materials and plant nutrients that tend to rot.
The main organic materials are food and vegetable waste, plant nutrient come from chemical soaps, washing powders, etc. Domestic sewage is also very likely to contain disease-causing microbes. Thus, disposal of domestic waste water is a significant technical problem. Sewage generated from the urban areas in India has multiplied manifold since 1947.
Important specific devices for control of water pollution are:
In some developed countries, thermal pollution abatement schemes are used to control water pollution. These methods include once-through cooling, cooling ponds, wet cooling towers, evaporative and dry cooling towers.
Recently American scientists have claimed to use solar power for purifying the polluted waste water cheaply. Experiment concluded that a combination of sunlight and a catalyst such as titanium dioxide can dissociate deleterious chemical pollutants of water. Such photolytic reactions may kill pesticides like DDT, PCBs, malodorous microbes and destroy explosive solvents, dioxins and cyanides.
New biological methods are now being considered for polluted water treatment. The use of shallow (near about 1 meter deep) oxidation ponds allows water to be purified by the action of aerobic bacteria and algae.
These ponds use solar radiation for photosynthesis and the organic material is used for both bacterial and algal growth, greatly reducing BOD (and also coliform organisms, perhaps through the production of antibiotic substances by the algae).
The ponds may have disagreeable odours if anaerobic conditions are permitted to exist but under proper conditions there is plenty of O2 produced and the effluent may even be supersaturated with DO. The ponds eventually have to be cleaned out (perhaps every few years) and weeds must be kept under control (this is part of the reason for keeping the ponds shallow).
Recently in Mississippi, the US National Aeronautics and Space Administration (NASA) at the National Space Technology Laboratories used water hyacinth (Eichhornia Crassipes) and duckweeds (Spirodela species, Lemna species and Wolfia species) to upgrade waste water treatment lagoons and to treat chemical waste water.
In fact, water hyacinth can be used as natural filters to absorb contaminated effluents from domestic and industrial sewage. Other pollutants like S, Ca, K, Fe and other minerals may be extracted from domestic sewage by harvesting the plant biomass. This harvested weed material is also a potential source of high quality protein, energy (biogas), fertilizer etc.
Water hyacinth may also absorb various organic compounds such as phenols, benzene, toxaphene etc. So much so, it can remove radioactive toxicants from effluents which are actually very difficult otherwise. Further, it effectively maintains the pH of water between 6.8 – 7.8. Moreover, it inhibits the algal bloom to develop and the BOD and COD are lowered to the level at which the effluent can be satisfactorily mixed without causing any nemesis in aquatic bodies.
Speech # 11. How to Stop Water Pollution?
The water-controlled environment is everything that surrounds us that gives us life and health. Destroying the environment of the water ultimately reduces the quality of our own lives, imperils us into immediate and long-term ill-health. That is why water pollution matters to all of us. There is no easy way to solve water pollution.
The people should be made to live a life that enriches their own as well as the community of which they are a part. There are laws concerning the protection of water quality, but it has been established world over that the laws alone prohibit the people from polluting the water which they use for their own consumption. Therefore, apart from Laws, Education and Economics make things work together as a team.
Awareness to the problems caused by water pollution to the health and happiness is the first education to the citizens, irrespective of their age, to solving it. Public awareness on the right for clean water can make a positive difference in the availability of germ-free water for all purposes of day-to-day activities of the humans as well as the flora and fauna.
The Environmental laws concerning Water are so stringent that it is difficult for people to pollute the rivers and water bodies if they are shared by many countries. There are tough international laws governing the oceans, such as- (a) the 1982 UN Convention on the Law of the Sea, signed by over 120 nations, (b) the 1972 London (Dumping) Convention, (c) the 1978 MARPOL International Convention for the Prevention of Pollution from Ships, and (d) the 1998 OSPAR Convention for the Protection of the Marine Environment of the North East Atlantic.
Most countries also have their own water pollution laws. In India, we have “THE WATER (PREVENTION AND CONTROL OF POLLUTION) ACT, 1974” enacted on 23rd March, 1974. This is “An Act to provide for the prevention and control of water pollution and the maintaining or restoring of wholesomeness of water, for the establishment, with a view to carrying out the purposes….for the prevention and control of water pollution…”. This Act was subsequently amended by Act No.53 of 1988 dated 11-08-1989.
The concept of ‘economics’ in the domain of ‘cleanliness of water’ is hinged to the preserving and restoring the ‘cleanliness of the water source’, rather than doling out benefits to the people for maintaining the cleanliness. Most of the global environment specialists recommend that the only way to tackle the water pollution is through ‘the polluter pays’ principle.
This means that whoever causes pollution should have to pay to clean it up. Polluter pays might mean that the oil tanker owners should have to take out insurance that covers the cost of oil spill cleanups. It could also mean that shoppers should have to pay for their plastic grocery bags to encourage recycling and minimize waste. It could also mean that factories that use river water must have their water inlet pipes downstream of their effluent outflow pipes.
This arrangement would ensure that if they cause pollution to the river, they themselves would suffer, and on that count they would take adequate precautions. The polluter pays principle is designed chiefly to deter the people from polluting by making them to behave in an environmentally responsible manner.
It is desirable that in India too we have rules comparable to the polluter-pays, because in places where the seriousness of environment protection, pollution control and public health concerns are viewed not so seriously, inculcation of concerns on these matters need to be developed as habit.
The starting point for initiation of these habits should be from the childhood, and therefore, the schools need to pay attention on enforcing environment-conscious behaviours at very young age. It needs a generation to pick up good habits, shape and transform themselves into environment-conscious citizens, and therefore, the seeds for cultivating habits which show concern for the protection, preservation and restoration of healthy environment of water and the water- bodies should be sown in the fields of learning like schools and other educational institutions.
Speech # 12. Methods for Minimizing the Problem of Water Pollution:
Improvements in water quality, availability and excreta disposal have been shown to yield major reduction in arborz disease as well as improvements in nutrition and decline in communicable diseases. Transmission of microbes occurs through drinking water, person to person contact and food intake.
The effectiveness of interviewing in each of these channels of transmission to reduce the total number of microbes transmitted to the host have been extensively tested and the evidence shows that in improving water quality it is a necessary step.
The physical quality of water includes colour, taste, turbidity and temperature. Ground water, unlike surface water, is generally clear and colourless with little or so suspended matter and relatively constant temperature. Because of these characteristics, ground water in most hydrogeological situations can be put to direct use without treatment to improve the physical quality.
Chemical analysis forms the basis of interpretation of the quality of water in relation to source, geology, climate and use. The chemical composition of ground water is related to the soluble products of rock, weathering, decomposition and changes with respect to time and space.
Large scale ground water development results in changes in the water chemical balance, often increasing the concentration of certain substances beyond acceptable levels. The environmental implications of large scale ground water development, especially for irrigation and industry, are becoming increasingly evident. Geochemical studies thus, provide a complete knowledge of the water quality.
The evaluation of water quality for human health and accordingly the concentration of individual ions and trace elements have been discussed as under:
High concentration of chloride give an undesirable taste to water. Infants and children may suffer if they consume water high in chloride as their delicate kidney tissue may be damaged by the higher osmotic pressure brought about by the presence of high concentration of salts. It is, therefore, important that the chloride content of water supply should be kept in the range of 250 mg 1–1.
High concentration of sulphate in association with sodium or magnesium in the drinking water may give rise to gastro-intestinal irritation. At higher concentration sulphate has a laxative effect.
There is evidence that death rate from cardiovascular diseases are inversely correlated with the hardness of water, but there is insufficient proof that either the calcium or magnesium in water is directly involved.
As per WHO recommendations the intake of sodium should be reduced in order to protect human health because sodium contributes to the increased incidence of high blood pressure and is possibly responsible for some cardiac failures.
The concentration of potassium is generally low in ground water. Potassium salts are of therapeutic value in the treatment of familiar periodic paralysis. No desirable or excessive limit for potassium have been set.
Calcium is an essential element and human body requires 0.7 to 2.0 gm per day. Larger doses may be required frequently by lactating women or growing children. The absence of calcium in very soft water have been considered responsible for rickets, decayed teeth, etc., while water having higher concentration of calcium may cause urinary disorders.
It is one of the constituents responsible for hardness of water. Although low concentrations are not harmful, higher concentration may cause laxative effect.
TDS consist of inorganic substances. Indian Council of Medical Research while recommending 500 TDS in potable water also laid down maximum limit of 1500 mg 1–1.
There is no evidence of harmful effects associated with the relatively low levels. It becomes toxic when concentration exceeds 1 mg 1–1. At levels above 1.5 mg 1–1, mottling of teeth has been reported. At 3.0-6.0 mg 1–1 skeletal fluorosis may be observed. When a concentration of 10 mg 1–1 exceeded it may cause crippling problem.
Nitrate in concentration greater than 45 mg 1–1 is undesirable in domestic water supplies because of the potential toxic effect on young infants, although adult and older children are not affected. Methemoglobinemia is a disease caused by nitrate poisoning and the sign of this disease is listlessness and a bluish tinge to the skin.
Iodine is an element actively involved in the metabolic action of human beings. General requirements 150-200 mg 1–1 per day. Most people recognise a large, unsightly swelling in the neck, called arbor, which is caused by severe deficiency of iodine in the diet. Fewer realize that iodine deficiency disorders are the largest preventable cause of mental retardation and congenital neurological disorders. Around 250 million people in India are living in iodine deficient areas.
These people may appear normal but most of them are suffering from invisible signs of deficiency manifested in a slight decrease in energy levels, marginal fall in IQ and slowness in fine motor skills. Iodised salt is the ideal solution to check the diseases caused by iodine deficiency.
Microbiological contamination of drinking water is main cause of large amount of communicable and waterborne diseases. Reliable estimates indicates that diseases resulting from microbiological pollution of drinking water are far greater than that from chemical contamination. Certain bacterial protozoan and helminthic diseases are commonly or exclusively waterborne. Disease causing bacteria are known as pathogen bacteria. The presence of coliforms in ground water indicate the possibility of the presence of pathogenic bacteria.
The risk of waterborne infection depends on the dose of pathogens ingested. Different pathogens have different infective doses. While millions of vibrio cholera organism are needed to cause an infection, fewer (103) are necessary in the case of Shangella, which causes bacillary dysentery.
The diseases transmitted through microbiological contamination of water in India are diarrhoea and dysentery of various types (including cholera), typhoid and hepatitis A. Other water-borne diseases skin infections, intestinal infestations and trachoma.