Selina Concise Solutions for ICSE Class 9 Biology Chapter 19 Waste Generation And Management

Exercise 1

Question 1:
Answer: (a) Old newspapers
Old newspapers are made from organic wood pulp and are completely biodegradable, which means they can rot and return to the earth. Recycling them is a great way to save energy and protect our forests from being cut down.
Teacher's Tip: Think of paper as "transformed trees" to remember it is a degradable organic waste.
Exam Tip: In multiple-choice questions, always write the full text of the option for complete clarity.

Question 2:
Answer: (a) plastics
Plastic is a synthetic material that does not break down naturally, so it can stay in our environment for hundreds of years. It is important to reduce our use of single-use plastics to protect our oceans and wildlife.
Teacher's Tip: Avoid plastic by using "Reusable" items like metal bottles or cloth bags.
Exam Tip: Always categorize plastic as "non-degradable" when discussing waste management strategies.

Question 3:
Answer: (a) Sludge
(b) Scrubber, Plate type electrostatic precipitator
Sludge is the thick, semi-solid material that is left over after the primary treatment of wastewater in a sewage plant. Scrubbers and precipitators are high-tech machines that clean industrial smoke to prevent air pollution.
Teacher's Tip: Think of a "Scrubber" as a giant "Air Washer" that cleans factory fumes.
Exam Tip: Learn the correct spelling of "electrostatic precipitator" as it is a common technical term in science exams.

Question 4:
Answer: (a) True
(b) True
(c) False. Electricity is one of the secondary needs of human society.
Primary needs are things like food, water, and air which are essential for staying alive. Secondary needs, like electricity and cars, make our modern lives easier and more comfortable but are not strictly required for survival.
Teacher's Tip: Primary = Survival, Secondary = Civilization and Comfort.
Exam Tip: When a statement is false, providing the corrected fact helps you score full marks.

Question 5:
Answer: 1. Cow dung - (iii) Manure
2. Bagasse - (i) Sugarcane
3. Old newspapers - (ii) Raddiwalas
Bagasse is the dry fiber that remains after sugarcane is crushed to extract juice, often used as fuel or to make paper. This matching shows how different types of waste can be reused or recycled by different people and industries.
Teacher's Tip: "Raddiwalas" are the local heroes of recycling in India as they collect paper and metal for reuse.
Exam Tip: Match the waste product to its specific source or reuse method as taught in the textbook.

Question 6:
Answer: DEGRADABLE WASTE: The waste that can be decomposed by micro-organisms is called degradable waste. E.g. Vegetable peel, paper, cloth etc.
NON-DEGRADABLE WASTE: The waste that cannot be decomposed by micro-organisms is called non-degradable waste. E.g. Plastic
Degradable waste is broken down by tiny living things like bacteria and fungi, which turns the waste back into soil nutrients. Non-degradable waste stays in the environment forever unless it is physically recycled or carefully buried.
Teacher's Tip: If it used to be a living thing (plant or animal), it is usually degradable.
Exam Tip: Include at least two examples for each category to demonstrate a complete understanding.

Question 7:
Answer: (a) Broken glass utensils are a kind of non-degradable waste as they cannot be decomposed and broken down by living micro-organisms. These need to be disposed off in deep dug out pits so that they do not cause any harm. However, sometimes broken glass in large quantities can be used in glass industries after melting them.
(b) Landfills are coming up fast near large cities due to huge population growth and lack of using efficient and safe disposal method. As construction activities are very active, new colonies are being raised and construction units have become very active. These produce large quantities of waste stones, pebbles, broken bricks and wood waste. Mostly, these are used as landfills. One can see heaps of landfills in the suburbs.
(c) Municipal sewage is first separated into degradable and non-degradable wastes because degradable wastes can be broken down into non-toxic waste in septic tanks, while non-degradable waste needs to be dumped or buried at safe places to avoid any hazardous effects.
Managing glass, construction debris, and sewage is a major task for every modern city to maintain public health. Separation of waste at the source makes it much easier to treat sewage and recycle materials like glass.
Teacher's Tip: Glass is made from sand, so melting it down to make new glass saves a lot of energy.
Exam Tip: When discussing landfills, mention "construction waste" as a major contributor in urban areas.

Question 8:
Answer: Electronic waste is the waste generated by discarded electrical appliances.
Items which come under the category of electronic waste:
1. Fluorescent tubes
2. Medical instruments
3. Toys
4. Lead acid batteries
5. Mobile phones
6. Radios
E-waste is particularly dangerous because it often contains toxic metals like lead, mercury, and cadmium that can leak into the ground. As we buy more gadgets, we must find better ways to recycle these complex machines safely.
Teacher's Tip: If it has a battery or a plug and you don't need it anymore, it is E-waste.
Exam Tip: "Lead acid batteries" and "mobile phones" are excellent specific examples to include in your list.

Question 9:
Answer: Common wastes produced in mining operation:
Coal, Dust, Iron, Copper, Zinc, etc.
Reusing of wastes produced in mining operation:
During operation of getting minerals, a large quantity of waste material is produced. This waste material is called mine tailing. It is the left over. The mine tailing can be mixed with materials to produce tiles and masonry cement.
Mining produces massive amounts of rocky leftovers because only a tiny fraction of the earth dug up contains the actual metal or mineral. Turning these leftovers into building materials like cement is a clever way to reduce industrial waste.
Teacher's Tip: Think of "Mine Tailings" as the "scraps" left on the plate after a giant mineral meal.
Exam Tip: Use the term "mine tailing" to describe mineral waste for higher technical marks.

Question 10:
Answer: The rotting and conversion of organic waste into manure is known as composting. The product formed after composting is called compost.
Method of preparing compost:
1. A trench of about 5m long, 1.5 m wide and 1.5 m deep is dug.
2. A 30cm thick layer of well-mixed refuse and waste is spread on it. This layer is completely wetted with a watery mixture of cow dung and some mud.
3. A second layer of mixed refuse is spread over the first layer, till the heap rises about half a metre.
4. The set-up is kept undisturbed for about 3 months, during which water is sprinkled over it at regular intervals.
5. A trench is then dug, its material is taken out and rearranged in conical heaps and covered with a layer of soil.
6. After 50-60 days, compost is ready for use in cultivation fields or in garden flower beds, etc.
Composting turns kitchen scraps and garden waste into a rich, natural fertilizer that helps plants grow stronger. It is a biological process that mimics how nature recycles nutrients in a forest.
Teacher's Tip: A good compost pile needs a bit of water and air to help the bacteria do their work.
Exam Tip: Remember the time duration; it takes about 3 months for the first stage and another 2 months for completion.

Question 11:
Answer: Usefulness of incineration of wastes:

• It reduces the weight of the waste.
• It reduces the volume of the waste.
• It renders toxic wastes into less toxic or even non-toxic wastes.

Precautions required for incineration:

• It should be carried out at very high temperatures.
• It should be equipped with pollution control devices.
• It should be installed away from residential areas.

Incineration is the process of burning waste in a specialized furnace to turn it into ash, which takes up much less space. It is the best method for destroying medical waste because the high heat kills all germs and pathogens instantly.
Teacher's Tip: Incineration is like a "Super Fire" that shrinks trash into a tiny pile of ash.
Exam Tip: Mention "pollution control devices" to show that incinerators must be environmentally safe.