The word pollution derived from the latin word ‘pollutionem’ meaning defilement. Today water resources have been the most exploited natural system since man strode in earth. Pollution of water bodies is increasing steadily due to rapid growth, industrial proliferation, urbanizations increasing living standards and wide spheres of human activities. Time is, perhaps not too for when pure and clean water, particularly in densely populated industrialized water scarce areas may be inadequate for maintaining the normal living standards.
Even the most unpolluted geographically clean areas, the rainwater consisting of dissolved oxygen, nitrogen, co2, dust and particulates picked up from atmosphere added to the water. Now pollution of water bodies has becomes universal phenomenon in the present day world.
1.DEFINITION OF WATER POLLUTIONWater pollution may be defined in a number of ways.
Thus water pollution disturbs the normal use of water for irrigation, agriculture, industries, public water supply and aquatic life. It is now considered not only in term of public resources but also it represents the taste of state of deviation from pure conditions where by the normal function and properties are affected. Any shifts in the naturally dynamic equilibrium existing among environmental segments i.e. hydrosphere, atmosphere, lithosphere or sediments gives rise to the state of water pollution. Water pollution is mainly caused by natural process in which the decomposed vegetable, animal and weathered products are brought into main water resources. All these processes are interdependent on each other and lead to the deterioration of natural environment.
Anthropogenic processes such as industrial agricultural, urban, domestic, radioactive mining sources use of pesticides and fertilizers by man etc. These pollutants are constantly poured in to water and deteriorating it to such an extent that it becomes unfit for living communities.
Water pollution can be classified mainly in to four categories.
- Physical pollution of water
- Chemical pollution of water
- Biological pollution of water
- Physiological pollution of water
The physical pollution of water brings about change in water with regards to its colour, odour, taste, turbidity and thermal properties etc.
- COLOUR
Colour change is not harmful unless it is associated with a toxic chemical, but it may affect the quality of sunlight that penetrates to a given depth, inhibiting plant and animal metabolism. Most of the trade wastes discharged into water system have pronounced colors due to organic dyes and inorganic complexes. Water become intensely coloured due to interaction between naturally occurring components in water and trade effluent, which make it unsuitable for various purposes.
- TURBIDITY
- TASTE
Unpleasant earthy or musty taste and odour are produced by industrial effluent containing Fe, Mn, Free chlorine, phenol and aquatic actinomycetes Manganese, oil, hydrocarbons, Chlorophenols, petroleum products, synthetic detergents, pesticides etc, produce characteristic taste in water. The decomposed organic matter algae, fungi, bacteria and pathogens impart peculiar taste.
- ODOUR
5. FOAM
Foam is produced by soaps; synthetic detergent and untreated organic effluents from paper and pulp industries clean water can readily form foam. It decreases as the pollution increases.
6.THERMAL POLLUTION
It mainly arises by the discharge of unutilized heat produced in various thermal power plants. The hated water reduces the amount of dissolved oxygen content due to which organic matter degrades faster
1.3.2 CHEMICAL POLLUTION OF WATER
The chemical pollutions of water cause changes in acidity, alkalinity, pH, dissolved oxygen and other gases in water. It may be caused either by organic pollutant can be biodegradable or non biodegradable.
Non-biodegradable organic pollutants are those that persist in a aquatic system for a long time. For example pesticides, nematocides etc. The use of these organic compound in chemical ultimately find their way into near by water course. Several gases, toxic metal metals and compounds have been included in inorganic pollutant because they also degrade the water quality seriously.
1.3.3 BIOLOGICAL POLLUTION OF WATER
The excretory product of warm-blooded animals including man, wild and domestic animals causes biological pollution in water. Bacteria, virus, algae etc also bring about biological pollution.
1.3.4 PHYSIOLOGICAL POLLUTION OF WATER
GROUND WATER
POLLUTION
Today the accelerated pace of development, rapid industrialsation and population density have increased demand of water resources, ground water a gift of nature, is about 210 billion m3 including recharge though infiltration, sewage and evaporation out of this nearly one third is extracted fro irrigation industrial and domestic use while most of the water is regenerated in to river.
Ground water act as reservoir by the virtue of long pore space in earth materials as a contain which can transport water long and as a mechanical filter. Which improved water quality by removing suspended social and bacterial contamination. It is a source of water for well and springs, that is the recommended for rural domestic use.
Ground water contamination is generally irreversible once it is contaminated; it is difficult to restore the original water quality.
The extent of ground water pollution depend on the following factors (i) Rain fall pattern (ii) Depth of water table (iii) Distance from the sources of contamination and soil properties such as texture structure and filtration rate.
- SOURCE OF CONTAMINATION OF GROUND WATER
Under ground source of drinking water, especially in outskirts of large cities and village are highly polluted. Ground water is threatened with pollution from the following source such as domestic waste, industrial waste, agricultural waste, runoff from urban area and soluble effluents.
1.4.2 HARMFUL EFFECTS OF GROUND WATER POLLUTION
Ground water pollution causes irreparable damage to soil, plant and animals including man. Polluted water is the major causes fro spread of epidemics and erotic disease in man. It causes typhoid, hepatitis, dysentery, and tuberculosis. Water contaminated by fibers i.e. asbestos causes fatal diseases like lung cancer ground water in excessive rainfall area contamin iron in topic amount as 20 ppm in deep tube wells, iron exists as ferrous ion which on taking out rapidly changes to light yellow orange colour due to oxidation and precipitation as ferric hydroxides.
- WATER QUALITY
Experience has shown that many divers factors will have to be taken into account before making comment on water quality. For this reason the concentration of inorganic and organic substance dissolved in a body of water their spatial and temporal variation need to be monitored. It has been classified on the basis of their total dissolved solid contents as given in table 1.1.
TABLE 1.1 WATER QUALITY Vs TOTAL DISSOLVED SOLID
Water Quality | Total Dissolved Solid (mg/l) |
Fresh | Less than 1000 |
Slight saline | 1000 to 3000 |
Moderately saline | 3000 to 10000 |
Very saline | 10000 to 35000 |
Bring | Grater than 35000 |
The underlying chemical relationship between pH, alkalinity, hardness, the ratio of sodium to that of calcium and magnesium etc. determines the buffering capacity, deposit formation and corrosive nature of water.
TABLE 1.2 CHEMICAL CONSTITUENTS OF SIGNIFICANCE IN NATURE WATER
Chemical Constituents mg/l Bicarbonate 150-200 Carbonates --------- Calcium --------- Magnesium 25-50 Sodium 60 (irrigation) Iron Less than 1 Manganese Less than 0.05 Chloride 200 Fluoride 0.7 – 1.2
1.5.1 DRINIKING WATER SUPPLIES
A case in point is the smell of chlorine that is once in a way detected in domestic water, supply, as a result of excessive chlorination with on increase in hardness of water its suitability decreases with respect to cooking, cleaning. One the well documented problem concerning drinking water is the presence of fluoride. There is also a certain amount of avoidable confusion since the beneficial effect of a little fluoride in dental case is also known.
TABLE 1.3 WHO GUIDELINES (1984) FOR ESTHETIC
QUALITY OF DRINKING WATER
Constituent | Unit | Guideline Value |
Chloride | mg/l | 200 |
Copper | mg/l | 1.0 |
Hardness | mg/l | 500 (as CaCo3) |
Iron | mg/l | 0.3 |
Manganese | mg/l | 0.1 |
pH | - | 6.5 to 8.5 |
Sodium | mg/l | 200 |
Sulphate | mg/l | 400 |
1.5.2 CHEMICAL PARAMETERS GOVERNING WATER QUALITY
It is essential to appreciate the significance of limit set on chemical parameter defining water quality. The hydrogen ion concentration is represented by the value pH. The electrical conductivity of water is related to its total dissolved solid content since it is easy to measure the parameter. It is a very useful indicator and is expressed as micro siemens/cm at 25.c.
TABLE 1.4 SPECIFICATION CONDUCTIVITY Vs WATER QUALITY
Specific conductivity (s/cm) | Water quality |
Less than 250 | Excellent |
250 – 750 | Good |
750 – 2000 | Permissible |
2000 – 3000 | Need treatment |
Greater than 3000 | Unsuitable for most purposes |
A commonly indicated water quality parameter is hardness, in presence of Ca and Mg in combination with anions such as carbonates and sulpahte. The presence of these two divalent cation is essential for ensuring soil permeability as well as for the growth of groups. Thus one measures about is known as Ca hardness Mg hardness and sum of these two viz the total hardness.
TABLE 1.5 HARDNESS Vs WATER QUALITIES.
Hardness in mg/l CaCo3 | Description of water |
0 – 50 | Soft water |
50 – 100 | Moderately soft |
100 – 150 | Neither bard or soft |
150 – 200 | Moderately bard |
200 – 300 | Hard water |
Bore water 300 | Very hard |
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