After reading this paragraph, you will learn about Water Pollution:- 1. Subject-Matter of Water Pollution 2. Water Chemistry 3. Types 4. Nature 5. Causes of Water Quality Degradation.
Paragraph Contents:
- Paragraph on the Subject-Matter of Water Pollution
- Paragraph on Water Chemistry
- Paragraph on the Types of Water Pollution
- Paragraph on the Nature of Water Pollutants
- Paragraph on the Causes of Water Quality Degradation
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Paragraph # 1. Subject-Matter of Water Pollution:
Water is one of the most important constituents of life support system.
It is indeed a wonderful chemical medium which has unique properties of dissolving and carrying in suspension a huge varieties of chemicals.
Thus it can get contaminated easily.Natural surface water bodies often have impurities from various sources.
The impurities may be suspended particles, colloidal materials and may also be dissolved cationic and anionic substances.
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The details are given in Table 11.1. Various kinds of natural and man-made activities—industrial, domestic, agricultural and others—are day by day creating water pollution problem, particularly in fresh water system. Time has come to work together in war footing to combat water pollution challenges with new protections to give all our children the gift of clean and safe water in the 21st century.
Paragraph # 2. Water Chemistry:
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To understand water pollution, it is essential to know the chemical phenomena that occur in water. The chemical phenomena includes acid-base reaction, solubility, oxidation-reduction and complexation reactions. Acid-base phenomena in water involve loss and acceptance of H+ ions.
Many species act as acids in water by releasing H+ ions, others act as bases by accepting H+ ions, and the water molecule itself does both. An important species in the acid-base chemistry of water is bicarbonate ion, HCO3, which may act as either an acid or a base:
Various gases viz., O3, CO2, NH3, CI, SOX, NOX etc. are soluble in water along with different salts and mostly maintain an equilibrium of ions.
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Oxidation-reduction phenomena are highly significant in the environmental chemistry of natural water and wastewater. In a lake, for example, the reduction of oxygen (O2) by organic matter (represented by CH20). [CH2O + O2 → CO2 + H2O], results in oxygen depletion that can kill fish.
The rate at which sewage is oxidised is crucial to the operation of a waste treatment plant. Reduction of insoluble iron (III) to soluble iron (II), [Fe (OH)3(S) + 3H+ + e → Fe2+ + 3H2O] in a reservoir contaminates the water with dissolved iron, which is hard to remove in the water treatment plant. Oxidation of NH4 to NOJ in water converts ammonium nitrogen to nitrate, a form more assailable by algae in the water.
NH4 + 2O2→ NO3 + 2H+ + H2O
The chelating agents are common potential water pollutant and thus forms various metal complexes.
Paragraph # 3. Types of Water Pollution
a. Ground Water Pollution:
The ground water is most prime water which have multipurpose uses ranging from drinking to industrial and agricultural uses. The quality requirement varies distinctly with respect to the specific uses. For instance drinking water must have specified quality (Table 11.1), which is not at all essential for industrial purposes or other domestic uses.
Though ground water appears to be less prone to pollutant mixing yet there are a number of potential sources of ground water pollution (Table 11.2). Ground water contamination with arsenic, fluoride, and nitrate recently possess serious health hazards to large sector of communities all over the world. Most illustrated accounts of ground water pollution is further described in 11.2.
b. Surface Water Pollution:
Major lakes, rivers, reservoirs of the world are now getting polluted by various ways (Table 11.3), and thereby posing threat to the survivability of the life systems on these diverse water bodies. There are a number of routes of entry of pollutants to the surface water.
Regular monitoring of these contaminating routes and their effective protective action plan has to be evolved for better conservation of surface water resources in future. Water quality status of some rivers of India is depicted in Table 11.4.
Paragraph # 4. Nature of Water Pollutants:
There are diverse categories of water pollutants often encountered in nature. They are primarily high nutrients like PO4, NO3, CO3 or SO4; acidity or alkalinity of water, contamination of toxic metals, high particulates load, contamination with pathogenic microbes and pesticides, presence of oils, grease and other hydrocarbons etc.
These contaminants causing detrimental effects on aquatic biota or its consumption in any form cause serious health hazards. In addition, higher water temperature may also cause detrimental effects on aquatic biotic life too. A generalized list of common water pollutants is given in Table 11.5.
The eutrophication is a nutrient enrichment (mostly nitrate and phosphates) in water bodies. This is quite common in confined water bodies like lakes and reservoirs. The sign of eutrophication is manifested by a number of features viz., phytoplankton bloom, higher macrophyte growth and depletion of oxygen level of water.
The eutrophication is primarily caused by anthropogenic or cultural activities of mankind. Sewage contamination, waste dumping in water bodies or even agricultural run-off storage leads to eutrophication.
After the planktonic bloom or macrophysics growth nutrients are reduced due to plants uptake, then finally water bodies became much more less polluted. There is distinct loss of species diversity due to eutrophication of water bodies.
In lentic and lotic water bodies, there is an intimate relationship of nitrogen and phosphorus cycling and sunlight. For instance, if in a water body the ratio of phosphate to nitrate is 1:15, the aquatic plants will be able to use all phosphates but only about half of the nitrate i.e., the phosphate becomes limiting and nitrate in abundance.
But keeping the nitrate at the same level, if phosphate enrichment takes place say to 4:15 phosphate; nitrate level, then all nitrates will be used by plants and it becomes limiting. The acceptable level of total inorganic phosphate in water is 0.03 to 0.40 mg/l. In most of the lakes and rivers of topics where eutrophication is encountered, the principal cause is excessive enrichment of water by phosphate and nitrates.
In and around cities and industries, phosphate content has increased by 20 – 25 folds during the last 10-15 years. Formation of froths and foams in lentic and lotic waters are due to phosphate containing detergents now profusely used for washing clothes.
Paragraph # 5. Causes of Water Quality Degradation:
On the whole, the quality of water degrades by a number of reasons. The principal reasons are stated in Table 11.6. It is very interesting to note the fact that due to the manner in which we have wasted our fresh water resources—either by the surface loss or by pollution—we have to face the crisis in couple of years.
Portable water will be a precious commodity in the long run. Already we have seen that potable mineral water used for drinking is costlier than milk which is considered to be a ‘balanced food’. This situation will further aggravate in coming decades. Multinational companies are already taking appropriate steps for marketing such potable mineral water in tropical countries.
