Science 3 Marks Question

In our country, a large number of people even today do not have sewerage facilities and thus defecate in open fields, railway tracks, etc. The untreated human excreta thus pollute soil and water sources including the underground water. When this contaminated water is used for drinking, it can cause diseases such as cholera, typhoid, hepatitis, dysentery, etc. which may even lead to death.

Therefore, lack of sanitation resulting in drinking of contaminated water can cause health problems.

Bar screen

In a wastewater treatment plant, bar screen removes large solid objects from water. The wastewater is allowed to pass through bar screen so that large solid objects such as rags, napkins, sticks, cans, plastic bags, polythene, etc. present in wastewater can be removed

Sewage contains various contaminants including disease-causing bacteria and other microbes. If untreated sewage is discharged into rivers or seas, then the water in the rivers or seas would also get contaminated. If this contaminated water is used for drinking, then it can cause diseases such as cholera, typhoid, dysentery, etc. which may lead to death. That is why it is harmful to discharge untreated sewage into rivers or seas.

• Leakage in sewer lines should be checked & repaired regularly.
• Do not defecate, spit or scatter litter in public places.
• Used tea leaves, solid food remains, toys, towels etc. should not be thrown in water pipe because these materials may choke the pipe.

• People take baths and wash clothes in rivers and lakes.
• Many people bathe their animals in rivers and lakes.
• Increase in the population, industries and improper disposal of waste.

• Sullage water: Waste water released from the kitchen is called sullage water. The contaminants in sullage water are mild detergents, oils and food particles. Moreover, it contains lots of water released when utensils are washed.
  
• Foul waste: Waste water released from toilets is termed as foul waste. It consists of human waste and a lot of bacteria that release gases and bad odour. It is highly infectious.
  
• Trade waste: Waste released from industries and commercial organisations is called trade waste. It consists of acids and strong chemicals that are toxic in nature.
  

1. By not throwing used tea leaves, solid food remains, etc. in the drain. We should throw it in the dustbin.
2. By not throwing chemicals like medicines, paints, insecticides, etc. in the drain as they increase the pollution load of the sewage.

1. Bathing of cattle in river bodies.
2. Washing of clothes & utensils by people in rivers.
3. Discharging wastes from factories, industries in nearby river bodies & ponds.

1. We should not throw used tea leaves into sink because it may choke the drain-pipe of the sink and do not allow the free fall of waste water through them.
2. We should not throw cooking oil and fats down the drain because cooking oil and fats down the drain as it can harden and block the drainage pipes. And in an open drain, the fats clog the soil pores reducing its effectiveness in filtering water.

1. The different types of inorganic and organic impurities present in sewage are as below.
2. Inorganic impurities – nitrates, phosphates and metals.
3. Organic impurities – fruit and vegetable wastes, oil, urea, human faeces, animal waste, pesticides and herbicides.

1. The settled solids that are removed in wastewater treatment with a scraper is sludge.
2. Water from kitchen which is used for washing dishes is wastewater.
3. Wastewater released from homes, industries, hospitals and other public buildings is sewage.

1. Ensure that his surroundings (both inside and outside home) are clean.
2. Ensure that the sewerage system in his house is properly managed.
3. If he notices some leakage or other problem in the sewerage system, he should report it to the municipality.

1. Use an aerator to bubble air through the wastewater. A mechanical stirrer or a mixer can also be used in place of the aerator. This helps in reducing bad odour of the wastewater.
2. Then, the water is filtered through the layers of sand, fine gravel, and medium gravel. Filtration makes the wastewater clean from various types of pollutants. The water is filtered continuously until it becomes clear.
3. Then any disinfectant such as chlorine tablet is added to the filtrate and stirred to obtain completely clear water.