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Q1. Which of the following are used for the safe disposal of human excreta in those areas where sewerage system does not exist and water supply is limited or not available at all?

• 1) Septic tank toilets
• 2) Chemical toilets
• 3) Composting toilets
• 4) Vacuum toilets

Solution

A composting toilet is a self-contained human waste disposal unit which is not connected to a sewer line. It breaks down and dehydrates human waste to a compost which can be added to soil to make it fertile. 

Q2. Name any three water borne diseases

Solution

Water-borne diseases include cholera, typhoid, polio, meningitis, hepatitis etc. (Any three)

Q3. Why it is that cooking oil and fats should not be thrown down the drain? Where should they be thrown?

Solution

Cooking oil and fats should not be thrown down the drain as it can harden and block the pipes. In an open drain, the fats clog the soil pores reducing its effectiveness in filtering water. We should throw cooking oil and fats in the dustbin.

Q4. Increase in the concentration of toxic waste per trophic level is called

• 1) Eutrophication
• 2) Biological oxygen demand
• 3) Chemical oxygen demand
• 4) Biological magnification

Solution

Increase in the concentration of toxic waste per trophic level is called biological magnification.

Q5. Name two inorganic impurities present in sewage.

Solution

Two inorganic impurities present in sewage are nitrates and phosphates.

Q6. How can we maintain sanitation in public places?

Solution

Sanitation in public places can be maintained by: 1. Use of dustbins for throwing litters 2. Use of public toilets for urination and defecation. Example- Sulabh 3. Use of handkerchief or tissue paper while sneezing or coughing in order to prevent air-borne diseases

Q7. Why should used tea leaves, solid food remains, etc not be released in the drains?

Solution

Used tea leaves, solid food remains, etc should not be thrown down the drain as they may choke the drain.

Q8. Write any six ways in which we use clean water at home.

Solution

(i) Drinking (ii) Bathing (iii) Washing utensils (iv) Brushing (v) Washing clothes (vi) Mopping floor

Q9. Why is sewage said to be a complex mixture?

Solution

Sewage contains many substances in it like suspended solids, organic and inorganic impurities, nutrients, saprotrophic and disease causing bacteria and other microbes. Hence it is said to be a complex mixture.

Q10. What are septic tanks? Give two examples of places where they are used.

Solution

Septic tanks are low cost onsite sewage disposal systems suitable for places where there is no sewerage system. It can be used for hospitals, isolated buildings or a cluster of 4 to 5 houses.

Q11. How is sludge treated?

Solution

The sludge is transferred to a separate tank where it is decomposed by anaerobic bacteria. The biogas produced can be used as a fuel and the dried sludge is used as a manure for replenishing the nutrients of the soil.

Q12. Explain why is it harmful to discharge untreated sewage into water bodies.

Solution

It is harmful to discharge the untreated sewage into the water bodies as it contains harmful substances. Most of it is water which has dissolved and suspended impurities which may pollute the water bodies and also harm the aquatic plants and animals.

Q13. (a) What did the General Assembly of the United Nations announced the period 2005 - 2015 as? What was its aim in doing so?(b) What is sewage treatment?

Solution

(a) On 22 March 2005, the General Assembly of the United Nations proclaimed the period 2005 - 2015 as the International Decade for action on "Water for life". All efforts made during this decade aim to reduce by half the number of people who do not have access to safe drinking water. (b) Sewage treatment is a process of removing pollutants from waste water before it enters a water body or is reused.

Q14. What are the various causes of water pollution?

Solution

Water is polluted by various factors like: 1. Bathing of cattle in river bodies 2. Washing of clothes and utensils by people in rivers 3. Discharging wastes form factories, industries in nearby river bodies and ponds

Q15. Why are bacteria used in sewage treatment plants?

Solution

The bacteria decompose the suspended waste that include domestic wastes and other undesirable organic substances present in the clarified water. The activity of bacteria produces decomposed organic material from which solid waste is separated. This solid waste s used as manure.

Q16. What are the harmful effects of sewerage?

Solution

Accumulation of sewerage leads to: 1. Spread of various diseases 2. Water pollution 3. Discharge of sewerage in water bodies leads to excessive growth of algae

Q17. Write any two examples of low cost onsite sewage disposal systems.

Solution

Examples are septic tanks, chemical toilets and composting pits. (Any two)

Q18. To improve sanitation, ____________________ disposal systems are being encouraged.

Solution

onsite sewage

Q19. What is sewarage? Write its function.

Solution

A network of big and small pipes passing through the ground called sewers for bringing clean water and taking away waste water forms the sewerage. It carries sewage from the point of being produced to the point of disposal, i.e. treatment plant.

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