This article throws light upon the ten adverse effects of various water pollutants. Some of the adverse effects are: 1. Effects of Inorganic Water Pollutants 2. Effects of Organic Water Pollutants 3. Effects of Sewage and Domestic Wastes 4. Effects of Sediments 5. Effects of Synthetic Detergents and Others.
Adverse Effect of Water Pollutant # 1. Effects of Inorganic Water Pollutants:
a. Acidic pollutants are lethal to fish, most invertebrates and micro-organisms at pH below 4.0. Acid mine drainage is the major cause of fish kill.
b. Strong alkalies like NaOH and KOH are known to produce asphyxiation by the coagulation of gill secretions in fish.
c. Excess of inorganic pollutants like CO2-3, SO2-4 , Ca2+, Mg2+ make the water hard and unsuitable for boilers.
d. Soluble salts not only affect aquatic life but they also cause serious diseases in man. Nitrate coming from nitrogenous organic matter causes methaemoglobinemia in children in the range of 20 to 40 ppm.
e. WHO pointed out that shell fish can concentrate mercury to the level of 10 mg per kg. Mercury poisoning caused Minamata disease in Japan in 1953 and killed several people.
Adverse Effect of Water Pollutant # 2. Effects of Organic Water Pollutants:
a. Organic compounds in water undergo degradation and putrefaction by bacterial activity. They consume dissolved oxygen which is an essential requirement of aquatic biota.
b. Organic matter coming from domestic and agricultural land contains nutrients which nourish algal growth. There occurs a loss of all DO content resulting in dead pool of water.
Adverse Effect of Water Pollutant # 3. Effects of Sewage and Domestic Wastes:
a. Domestic sewage, which is primarily composed of spent water containing wine, faeces, soapy wastes, food materials and paper makes the water extremely anaesthetic.
b. Accumulation of sewage and domestic wastes in water bodies retards the self-regulatory capabilities of aquatic organisms. Self-purifying ability of water is lost and it becomes unfit for domestic purposes.
c. Sewage poses major threat to water courses. Today developed countries are fighting against thermal and chemical pollutants, while Indians have to combat with chemicals and pathogens with their limited resources.
Adverse Effect of Water Pollutant # 4. Effects of Sediments:
a. Sediments decrease fish population by blanketing fish nests, spawn and food supplies.
b. Suspension may cause thickening of fish gills which may lead to asphyxiation of the fish.
c. These result in less food availability and plant biomass.
d. Sediments make the water cloudy and increase the cost of water treatment used for culinary purposes. Due to turbid water, the hunting ability of fish gets curtailed.
Adverse Effect of Water Pollutant # 5. Effects of Synthetic Detergents:
a. Detergent enzymes are potential allergens and can cause serious complications if inhaled or when they penetrate the body through wounds or cuts.
b. Complex formation between NTA (nitrilotriacetate) and Hg or Cd increases the possibilities of transmission across the placental barrier into a foetus, thereby increasing the likelihood of birth defects.
c. NTA is degraded in waste treatment systems, but under anaerobic conditions it exists in some septic tanks. These NTA may persist and get back to a water-well system.
d. Phosphate, the major ingredient of most detergents, favours the luxuriant growth of algae which forms algal blooms. Such decomposing waters are known to produce toxins as strychnine which kill animals.
e. The surface active ingredients which are not easily degradable cause nuisance at sewage works by creating foam and froth. It has been reported that about 50% of these substances occur in the final effluents.
f. The increased use of syndets, which replace surface active agents like soap are able to produce foams even in very low concentrations, so aeration is not possible. As a result, the rate of re-aeration of river water as well as the efficiency of sewage purification is reduced.
g. Laboratory experiments have proved that water plants are adversely affected by syndets. They also produce foul tastes in water bodies.
Adverse Effect of Water Pollutant # 6. Effects of Pathogens:
a. Parasites are considerably harmful for man. Eggs of nematodes, hook worms and tape worms occur mostly in crude sewage. When such sewage is discharged into water bodies without treatment, contamination of water occurs resulting in danger to man and aquatic life.
b. The enteric diseases are transmitted mainly by drinking contaminated water or swallowing food. The pathogens most frequently transmitted through water cause infections of intestinal tract like typhoid, paratyphoid, amoebic dysentery, cholera, polio and infectious hepatitis.
c. Intestinal helminthes, i.e., Ascaris lumbricoides and Trichuristrichiura are also water borne. Entamoeba histolytica is the casual agent which causes internal amoebiasis and several extra-intestinal diseases.
Adverse Effect of Water Pollutant # 7. Effects of Radioactive Pollutants in Water:
Living organisms are considered as the prey for radioactive contaminants in water. As compared to organic poisons, injurious effects of radionuclides are exceedingly high.
a. Radioactive contaminants deposit on surface and ground water. This water consumed by plants during photosynthesis acts as a medium for radioactivity in them.
b. In living organisms, radiation produces a whole host of extremely hazardous species like H+, H2, H2O–, H2O+, e–, e+, HO2, H3O– and H2O2 etc., causing severe effects.
c. The radioactive materials in water react with proteins of aquatic invertebrates and appear to deactivate enzymes by breaking S—H—S hydrogen bonds. With enzyme inhibition, cell growth may continue, but cell division may be stopped.
d. Traces of radioactive materials present in water cause cancers, leukemia, eye cataract, DNA breakage and carcinoma in man.
e. Drinking water containing Rn-222, Ra-226 and Th-232 could accumulate dangerously in man causing somatic and genetic disorders.
Adverse Effect of Water Pollutant # 8. Effects of Eutrophication:
a. Eutrophication causes several physical, chemical and biological changes which considerably deteriorate the water quality.
b. During eutrophication, algal bloom releases toxic chemicals which kill fish, birds and other aquatic animals causing the water to sink.
c. Decomposition of algal bloom leads to oxygen depletion in water. Thus with a high CO2 level and poor oxygen supply, aquatic organisms begin to die and the clean water turns into a stinking drain.
d. Many pathogenic microbes, viruses, protozoa and bacteria etc. grow on sewage products under anaerobic conditions. It results into spread of fatal water-borne diseases such as polio, dysentery, diarrhoea, typhoid and viral hepatitis.
e. In India, Dal, Nagin, Loktak lake and Hussain sagar are seriously chocked by aquatic weeds affecting fisheries production, utility for aquatic flora and aesthetic value.
Adverse Effect of Water Pollutant # 9. Effects of Thermal Pollution on Aquatic Ecosystem:
a. Reduction in dissolved oxygen:
DO content is decreased in the warm water. Normal, biological reduction of DO level of the atmospherically unreplenished lower layer of water may give rise to anaerobic conditions leading to fish mortality.
b. Direct fish mortality:
There appear to be particular temperature ranges that are tolerated by fish and other related species. For example, lethal temperature for trout is 77°F, for yellow perch 88°F and for carp it is 85°F. Thus thermal death of fish may occur due to the action of heat on nervous system, inactivation of enzymes and coagulation of cell protoplasm.
c. Interference with reproduction:
The increased temperature triggers deposition of eggs by female. Other activities like nest building, spawning, hatching and migration etc. get disturbed by rising temperature.
High temperature increases activities in aquatic animals, which exhaust the organisms and shortens their life. Generally the speed of a chemical change is doubled for every 10°C rise in temperature. Daphie lives for 40 days at 8°C while 29 days at 21°C.
e. Increased vulnerability to disease:
Some bacteria such as, chondroccus grow rapidly with rising water temperatures. It is believed to be responsible for the massive kill of blue black salmon on the Columbia river.
f. Invading destructive organisms:
Sometimes hot water permits the invasion of highly destructive organisms. A best example is the invasion of Shipworms into New Gersey’s Oyster Creek.
g. Destruction of aquatic animals:
Power plants require enormous amount of stream water for cooling purposes, even 500 million gallons per day. So a large number of fish, plankton and insect larvae may be sucked into the condenser along with the cooling water and destroyed by thermal shock, water velocity and pressure.
h. Changes in algae population:
Blue green algae and diatoms have different tolerance ranges for water temperature. Enriched nutrients and increased water temperature promote blue-green algal blooms.
i. Disruption of food chain:
Heated water effluents disturb aquatic food chain.
Adverse Effect of Water Pollutant # 10. Harmful Effects of Industrial Pollutants:
a. Industrial effluents cause deleterious effects on living organisms and may bring about death or sublethal pathology of kidneys, liver, lungs, brain and reproductive system.
b. It has been reported that free chlorine discharged by factories near Mirzapur in UP had caused heavy fish mortality in river Sone near Dehrion-son in Bihar.
c. Mercury poisoning among aquatic organisms has resulted in crippling and often fatal diseases like Minamata in Japan (1953). Effluents sometimes contain upto 10 times the level of Hg in natural water.
d. Industrial effluents consisting of As, Pb and cyanide etc. cause cellular degeneration in brain which results in figidity, coma, stupor and numbness.
e. Some of the trade wastes contain pathogenic bacteria. For instance, the pathogen Anthrax bacilli is present in tannery wastes.
f. Industrial discharges impart colour, foul odour and turbidity to the receiving waters. They undergo putrefaction to form objectionable tastes.