Waste Generation and Management Class 9 ICSE — Selina Ch 19

Waste generation and management class 9 ICSE is the topic of Selina Biology Chapter 19. It answers a question every household faces: what happens to the things we throw away. The chapter defines waste, sorts it into five categories, and explains eight safe disposal methods. Later sections work through each category and method in turn. By the end, you should be able to name every waste type and connect disposal choices to pollution and human health.

Download Waste Generation and Management Class 9 ICSE Biology Chapter 19 PDF

Download the Waste Generation and Management Class 9 ICSE Biology chapter PDF from the Selina Concise textbook to revise offline or print for practice. It is the full chapter as printed in the book — 6 pages, 17 sections, 25 questions.

What is inside Chapter 19

6 pages · 17 sections · 25 exercise questions

• PROGRESS CHECK: 5 questions
• PROGRESS CHECK: 6 questions
• REVIEW QUESTIONS: 14 questions

19.1 WHAT IS A WASTE ?

Waste is any substance discarded after primary use, or worthless, defective and of no further use. That is the definition this ICSE chapter opens with. It matches the official CISCE Class 9 Biology syllabus. The rest of the section explains why waste has become a serious problem. Population growth has raised the demand for food, shelter and clothing. That demand has expanded towns, cities, farms, factories, roads and railways.

More people means more electricity, firewood, petroleum and nuclear energy use. Each of these generates its own waste. Human body wastes, livestock wastes, discarded equipment and agricultural leftovers all accumulate faster than before. The volume of waste grows with development itself. That is why the chapter stresses efficient disposal methods, and why those methods keep improving. You can browse the other Class 9 Biology chapters on this site to see how this topic fits the course.

19.2 CATEGORIES OF WASTES

The chapter groups waste into five broad categories. Each category gets its own subsection later in the chapter.

• Domestic waste from homes
• Industrial waste from factories and thermal plants
• Agricultural waste left after the consumable parts are taken
• Municipal waste, the overall output of a township
• e-waste from electrical and electronic equipment

The five together form the backbone for the disposal methods covered in the second half of the chapter.

19.2.1 DOMESTIC WASTE

An average home discards waste in five main material groups. Kitchen waste leads the list. Peelings of vegetables and fruits, shells from ground nuts, dry fruits and eggs, washing water from pulses and rice, stale food, used tea leaves and leftovers all fall here.

Plastics follow, with packings, wrappings, broken toys and discarded objects. Glass includes broken utensils, mirrors, containers, window panes and bulbs. Rags cover torn cloth, old sheets, blankets, worn-out clothing and footwear. Paper means newspapers and magazines, the most convenient reusable waste of all.

Old newspapers and magazines are often sold to raddiwalas, who pass them on for reuse. Waste paper is recycled in the paper industry. That is why the chapter calls paper the most convenient reusable domestic waste.

19.2.2 INDUSTRIAL WASTE

Industries differ, so their waste differs. Mining operations extract copper, silver, gold, zinc, iron and coal. They leave behind mine tailing, the leftover material. Mixed with other materials, mine tailing can make tiles and masonry cement.

Cement industries give out solid, liquid and gaseous waste. Solid waste goes to construction or landfills. Liquid waste is treated to remove harmful substances before release into rivers, ponds, lakes or the sea. The gaseous waste includes flyash. The chapter’s review questions test this point directly.

Flyash can make bricks, concrete and roofing sheets. Oil refineries produce poisonous gaseous and liquid waste. Gaseous waste is cleaned through cleaners, and the purified part is released. Liquid waste is processed and suitably dumped.

Construction units throw out waste stones, pebbles, broken bricks and wood. Most goes to landfills. Large towns often show heaps of these landfills in the suburbs.

19.2.3 AGRICULTURAL WASTE

Agriculture means cultivating the soil, producing crops and raising livestock. Its waste includes agricultural residues, the plant parts left after the usable portions are taken. Much of this residue feeds animals. Bagasse, the residue after sugarcane juice is extracted, serves as firewood or goes to the paper industry.

Pesticides and fertilisers collect in the soil. Irrigation and rain water wash them into rivers and ponds, causing pollution. Strict precautions are needed in their use. Animal waste, including cow dung and other faecal matter, is used to make manure.

So agricultural waste is not purely a problem. Much of it is reused, whether as feed, fuel or fertiliser.

19.2.4 MUNICIPAL WASTE

Municipal waste is the overall waste of a township. It includes household discharge of excreta from toilets, kitchen washings, and discharge from public toilets, hospitals, hotels, restaurants and offices. All of this is carried through sewers. The chapter calls it sewage.

Sewage is separated into two parts. The degradable part can be broken down chemically into non-toxic components. The non-degradable part cannot. Septic tanks degrade the degradable portion. The non-degradable portion is dumped or buried at safe places.

That separation explains why municipal sewage is treated differently from other waste. The two parts need different handling, so they are split at the source.

19.2.5 e-WASTE

e-waste is short for electronic waste, meaning discarded appliances that use electricity. Old computers, TVs, refrigerators, radios, mobile phones, batteries, fluorescent tubes, electronic toys, medical instruments and lead-acid batteries all qualify. The chapter treats e-waste as one of the fastest growing waste streams.

e-waste holds both dangers and value. Harmful substances include lead, cadmium and mercury. Valuable materials include gold, silver and copper. Generation is heaviest in large cities, though smaller towns now add to it as living standards rise.

Rag pickers and kabadis collect discarded gadgets. They remove usable components or extract secondary raw materials. These recycling processes can harm health, including cancers. Burning printed wiring boards releases harmful fumes. Their residues can enter food chains through crops.

Recycling must be done carefully under skilled supervision. Special e-bins should collect discarded e-waste. Municipal agencies should arrange final disposal.

19.2.6 SCIENCE TEACHING & RESEARCH LABORATORIES WASTES

Teaching institutes and research laboratories produce varied waste. Broken or discarded glass apparatus, condemned machines, waste chemicals, and animal and plant wastes from biology labs and culture rooms all count. This waste must go into deeply dug pits or be burnt in special enclosures.

Radioactive material needs special care. Carelessness threatens human health. The chapter cites a Delhi case where radioactive cobalt-60 passed to waste dealers. They dumped it in the open in a well-inhabited colony, and affected people suffered badly.

This is the chapter’s warning example. It shows why disposal rules exist and what happens when they are ignored.

19.3 METHODS OF SAFE DISPOSAL OF WASTES

Different wastes need different disposal methods. The chapter lists eight: segregation, dumping, composting, drainage, treatment of effluents, incineration, scrubbers and electrostatic precipitators. Each gets a subsection explaining how it works and when it applies.

These eight methods cover the full range of waste, from kitchen scraps to factory gases. Several appear again in the review questions at the end of the Class 9 ICSE biology chapter.

19.3.1 SEGREGATION

Segregation means separating refuse into three categories: reusable, degradable and non-degradable. Reusable waste includes paper — newspapers, old books and discarded exercise books. Even the bulk of examination answer books can be recycled. Metallic components are separated out and reused.

Degradable waste, such as vegetable and fruit peelings, can decompose into useful manure. Microorganisms drive this breakdown, so the chapter calls it biodegradation. Non-degradable parts, like certain plastics, are dumped.

The three-way split is the first step of most disposal systems. It decides what gets recycled, what rots into manure, and what must be buried.

19.3.2 DUMPING

Non-degradable waste goes into specially dug pits away from human habitations. That is the whole method. The chapter keeps this section brief because dumping is simple. The key requirement is distance. The pits must stay far from where people live.

19.3.3 COMPOSTING

Composting means putting waste organic matter to decay so it can fertilise agricultural land. The trench method follows clear steps. A trench of about 5 m long, 1.5 m wide and 1.5 m deep is dug. A layer of well-mixed refuse spreads in it about 30 cm thick.

That layer is wetted fully with a watery mixture of cow dung and mud. A second layer of refuse is spread until the heap projects about half a metre above ground. The setup rests for about 3 months. Then the material is taken out, rearranged in conical heaps and covered with earth.

About 50 to 60 days later, the compost is ready for fields or garden beds. A quick volume check: the trench measures 5 \times 1.5 \times 1.5 metres. Its volume is 11.25\ \text{m}^3. That is the space a single compost trench occupies.

In Delhi, “Okhla Khad” is made mainly from garbage and human sewage. A newer approach is dry composting toilets. These offer a hygienic and cost-effective answer to human waste disposal.

19.3.4 DRAINAGE

Fluid wastes other than sewage need a proper drain system. Without drains, watery fluids collect in pits and puddles. Those become breeding places for mosquitoes and other harmful insects.

Drainage is therefore a health measure as much as a waste method. It keeps standing water away, and with it the insects that breed there.

19.3.5 TREATMENT OF EFFLUENTS BEFORE DISCHARGE.

Industrial and municipal waste waters are treated in Effluent Treatment Plants before release into water bodies. The treatment happens in three stages.

1. Primary treatment — large debris is separated by sedimentation in tanks.
2. Secondary treatment — waste water goes to oxidation ponds, where microorganisms like bacteria and algae oxidise organic matter, releasing CO_2 and producing sludge that can be used as manure.
3. Tertiary treatment — dissolved chemicals, metals and pathogens are removed. Then the water is discharged into natural waters or used for irrigation.

Each stage removes a different class of pollutant. Primary handling clears the largest solids. Secondary breaks down organic matter. Tertiary deals with dissolved chemicals and pathogens. That is why the three cannot be skipped.

19.3.6 INCINERATION

Incineration is disposal by burning. It serves three purposes. It reduces the volume of waste, reduces its weight, and renders toxic wastes less toxic or even non-toxic. Its impact is real too. It releases fumes and harmful substances.

So precautions matter. Incineration needs very high temperatures. It needs pollution control devices. It must be installed away from residential areas.

The leftover after burning is about 25 percent of the original waste, left as ash. The ash goes to landfills. Worked pattern: if 100 kg of waste is burned, and about 25 percent remains, the ash left is 25 kg.

Advantages follow. Ash occupies much less landfill space. Residual bottom ash can yield metals. Heat from burning can generate electricity.

19.3.7 SCRUBBERS

Scrubbers remove gaseous and particulate air pollutants. Air passes through a dry or wet packing material. The air leaving a scrubber is dust-free. It is also free of certain gaseous pollutants that dissolve in the wet packing.

So a single scrubber handles two pollutant types at once. That makes it valuable where factory air carries both dust and gases.

19.3.8 ELECTROSTATIC PRECIPITATORS

Dirty air containing particulates passes through a chamber of electrically charged plates. Particles, which may carry natural charge, collect on the plates of opposite charge. The clean gas passes out. Electrostatic precipitators remove up to 90 percent of particulate matter from thermal plants.

So the two devices overlap but differ. Scrubbers catch gases too. Precipitators specialise in particulates. Choosing between them depends on what the air contains.

What to practise from Waste Generation and Management Class 9 ICSE

The chapter closes with three practice blocks. Work through them in order, then check your answers against the chapter text.

• PROGRESS CHECK 1 — 5 questions on categorising waste, bagasse, agricultural chemicals, sewage portions and e-waste items
• PROGRESS CHECK 2 — 6 questions on segregation categories, dumping, composting, sludge, incineration and particulate devices
• REVIEW QUESTIONS — 14 questions in four formats: multiple choice, very short answer, short answer and long answer

These map directly to the ICSE board exam formats. Multiple choice questions test recall of facts like which waste is most reusable. Very short answers ask you to name terms. Short answers ask for differences and reasons. Long answers require a full description of a procedure, such as how compost is made. If you are working through the book in order, Chapter 18 on health organisations came just before this one.

You can find the complete Class 9 ICSE book collection here.

Waste Generation and Management Class 9 ICSE frequently asked questions

What will I learn in waste generation and management class 9 ICSE biology?

You will learn what counts as waste, the five categories of waste, and eight safe disposal methods. The chapter covers domestic, industrial, agricultural, municipal, e-waste and laboratory waste. It then explains segregation, dumping, composting, drainage, effluent treatment, incineration, scrubbers and electrostatic precipitators.

What is the difference between degradable and non-degradable waste in Class 9 ICSE biology?

Degradable waste can be broken down chemically into non-toxic parts, usually by microorganisms. Non-degradable waste cannot. The degradable part of sewage is handled in septic tanks, while the non-degradable part is dumped or buried.

What is e-waste and why is it harmful in Class 9 ICSE?

e-waste is discarded electrical and electronic equipment, from phones and computers to batteries and fluorescent tubes. It is harmful because it contains lead, cadmium and mercury. Burning printed wiring boards releases poisonous fumes that can enter food chains.

What do scrubbers and electrostatic precipitators remove from air?

Scrubbers remove both gaseous and particulate air pollutants by passing air through dry or wet packing. Electrostatic precipitators remove only particulate matter, using charged plates to collect particles. Precipitators can remove up to 90 percent of particulates from thermal plants.

Why is municipal sewage separated into degradable and non-degradable parts?

The two parts need different treatment. The degradable part can be broken down in septic tanks. The non-degradable part must be dumped or buried. Separating them first makes each treatment step possible.

Reference: ICSE Class 9 Biology textbook material, chapter 19: Waste Generation and Management — CISCE-aligned.

More from this book

• Chapter 18: Health Organisations