- No.4. Justify the statement: house hold water is the reason of water pollution.
Answer. Use of detergents is increasing day by day for cleaning purposes in houses-and industries. It is because; detergents have strong cleaning action than that of soap even in hard water. They can work even in acidic solutions. But they have a major disadvantage over the soaps, as some of the detergents are non-biodegradable (cannot be decomposed by micro-organisms like bacteria). When household water containing these detergents is discharged in streams, ponds, lakes and rivers, it causes water pollution.
The detergent remains in the water for a long time and makes the water unfit for aquatic life. The phosphate salts present in detergents causes’ rapid growth of algae in water bodies, which floats over the surface of water. These plants ultimately die and decay. Decaying plants being bio-degradable consume O2 present in water. Thus, depletion of O2 results in death of aquatic life.
Domestic sewage contains a wide variety of dissolved and suspended impurities. They include food and vegetable waste, garbage, cans, bottles, chemical soaps, washing powder, etc. It also contains disease causing microbes. All these substances add to
- No.5. Explain agricultural effluents are fatal for aquatic I life.
Answer. Water pollution due to agricultural waste is because of use of fertilizers and pesticides. Fertilizers are used to make up the deficiency of nitrogen, phosphorus, etc., of the soil because of intensive cultivation of crops in the recent years.
On the other hand, pesticides are used either directly to kill or control the growth of pests. Pests may be weeds, herbs, insects, fungi, viruses, etc. They all damage crops and transmit diseases both to human beings and animals.
Agricultural effluents have dual effects:
(i) Intensive cultivation of crops causes these chemicals from fertilizer and pesticides to seep into the ground water commonly called leaching process. The high nitrate contents in ground water are mainly because of irrigation run-off from agricultural fields.
(ii) Sun-off from the agricultural land (where fertilizer and pesticides have been used), enters into ponds, streams or fivers. This water contains nitrate (NO3–) and phosphate (PO43-) salts. These substances results in a rapid growth of algae, floating over the surface of water. They prevent the sunlight and air (oxygen) to reach up to aquatic life. When algae dies, and decompose bacteria consume oxygen of the water for decomposition. As a result oxygen depletes in the water. Aquatic animals feel suffocation and ultimately die due to insufficient supply of oxygen.