Frank Solutions for Chapter 23 Safe Disposal of Wastes Class 9 Biology ICSE


Exercises


1. What are the most important steps in waste management?
Answer
The important steps in waste management are:
  1. Dematerialization of production by reducing the amount of raw materials use and energy used in production.
  2. Recycling wastes back into the production process.
  3. Recovery of some ingredients and / or treatment of wastes.
  4. Dispersal, dumping or storage.

2. What are the measures adopted to prevent the spread of disease from sewage water?
Answer
Following are the measures adopted to prevent the spread of disease from sewage water:
  1. Sewage water must be disposed off in a suitable manner to prevent large scale outbreak of diseases and toxicity to living organisms.
  2. They should not be allowed to collect in the open.
  3. Sewage should be treated in sewage treatment plants wherein the pathogens are destroyed.

3. Give two advantages of garbage incineration.
Answer
Two advantages of garbage incineration are:
  1. Incineration reduces the weight and volume of the waste by as much as 95%.
  2. It helps in the treatment of clinical wastes and toxic pathogens.
  3. It is designed in such a way that it can be also used to produce electricity. (Write any two)

4. What is Composting? What processes are involves in composting?
Answer
Composting is an effective way of disposing of wet garbage from households and biomass wastes from gardens.
The processes involves in composting are:
  1. Vegetable peels, fruit peels, food-scraps, twigs, dry leaves, grass clippings can be dumped into a pit or a big bin.
  2. Then soil is spread over this pile.
  3. Earthworms can be introduced into the compost pit to decompose the organic matter which enrich the compost. This method is called vermi-composting.
  4. The soil microbes break down the organic matter.
  5. The compost obtained is rich organic manure for the plants in the garden.

5. How is sewage water treated?
Answer
Sewage water is treated in three steps:
  1. Primary treatment – In this, the coarse and fine suspended , solids are removed by sedimentation, coagulation and precipitation.
  2. Secondary treatment – It is essentially a biological treatment process which involves the removal of colloidal and dissolved organic substances and some toxic chemicals.
  3. Tertiary treatment – Here, excess nutrients are removed to allow the reuse of that water.

6. Explain the working of an electrostatic precipitator.
Answer
An electrostatic precipitator removes particulates of less than 50mm size. The particulates are electrically charged and then attracted to oppositely charged plates for collection. The vibration of these plates removes the particulate matter to the bottom and the pollutant free air then escape to join the atmosphere.
Diagrammatic view of the working of eletrostatic precipatator

7. What is segregation?
Answer
Segregation is the separation of wet and dry wastes in order to dispose them safely. Household wastes consist of organic biodegradable matter as well as non-biodegradable matter. They should be segregated from each other using separate bins. Wherever possible, the non-biodegradable matter is recycled and used. The organic biodegradable matter i.e. wet waste must be separated from other dry wastes. They are collected by municipal workers and transported to a landfill.

8. Give two uses of incineration.
Answer
Two uses of incineration are:
  1. Incineration reduces the weight and volume of the waste by as much as 95%.
  2. It helps to destroy pathogens and toxins using high temperature, thereby playing role in the treatment of clinical wastes and certain hazardous wastes.

9. Explain the methods of disposal of liquid wastes.
Answer
Most liquid wastes contain both dissolved and suspended matters.
Treatment of such effluent involves the removal of contaminants and is done to prevent any adverse effects on receiving water or allow its reuse. Three steps are usually followed in the treatment of effluents:
Sewage water is treated in three steps:
  1. Primary treatment – In this, the coarse and fine suspended solids are removed by sedimentation, coagulation and precipitation.
  2. Secondary treatment – It is essentially a biological treatment process which involves removal of colloidal and dissolved organic substances and some toxic chemicals.
  3. Tertiary treatment – Here, excess nutrients are removed to allow the reuse of that water.

10. Give two-ecofriendly ways of treating kitchen wastes.
Answer
The two ecofriendly ways of treating kitchen wastes are:
  1. Composting
  2. Segregation of wet and dry waste.

11. Give two benefits of composting.
Two benefits of composting are:
  1. It is an eco-friendly method of disposing wet garbage from households and biomass wastes from gardens.
  2. The compost obtained acts as rich organic manure for the garden plants.

12. Each question has four options. Choose the correct answer:

(i) Sewage water is purified by
(a) microorganisms
(b) light
(c) fishes
(d) aquatic plants
Answer
(a) microorganisms


(ii) Composting is carried out from
(a) sewage sludge
(b) rubbish
(c) industrial wastes
(d) garbage and sewage sludge
Answer
(d) garbage and sewage sludge

(iii) Sewage sludge is used as
(a) manure
(b) biogas generators
(c) both (a) and (b)
(d) tipping
Answer
(c) both (a) and (b)

(iv) Sewage is broken down in
(a) primary treatment
(b) secondary treatment
(c) tertiary treatment
(d) all the above
Answer
(b) secondary treatment
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