Waste Generation and Management Chapter Notes | Biology Class 9 ICSE PDF Download

What is a Waste?

• Waste refers to any substance discarded after its primary use, considered useless, defective, or of no value.
• Rapid population growth has increased the demand for food, shelter, and clothing, leading to more waste production.
• Urbanization and industrialization have resulted in more towns, cities, agricultural fields, factories, roads, and railways, contributing to waste generation.
• Increased use of electricity, firewood, petroleum, and nuclear energy adds to human, livestock, agricultural, and equipment-related waste.
• Efficient waste disposal methods are continually being developed to manage the growing waste problem.

Categories of Wastes

Waste can be broadly classified into five main types: 
(i) Domestic waste, produced by households; 
(ii) Industrial waste, generated by factories, thermal plants, and similar facilities; 
(iii) Agricultural waste, consisting of residues left after extracting usable parts; 
(iv) Municipal waste, encompassing all waste from a township; and 
(v) E-waste, originating from discarded electrical and electronic devices.

Domestic Waste

Produced from households, including various types of waste generated daily.

Kitchen Waste:

• Vegetable and fruit peelings.
• Shells from groundnuts, dry fruits, and eggs.
• Washings from pulses and rice before cooking.
• Stale or rotten food items and used tea leaves.
• Leftovers from food dishes.

Plastics:

• Plastic packaging and wrappings.
• Discarded or broken plastic items, including toys.

Glass:

• Broken glass utensils, mirrors, containers, window panes, and electric bulbs.

Rags:

• Waste pieces of cloth, torn towels, handkerchiefs, old bedsheets, blankets, cushions, and worn-out clothing or footwear.
• Some rags are reused by the poor or sold to waste dealers (raddiwalas).

Paper:

• Daily newspapers and magazines, often sold to raddiwalas for recycling or reuse in the paper industry.

Industrial Waste

• Generated from various industries producing materials and articles, using raw materials and releasing solid, liquid, and gaseous wastes.

Mining Operations:

• Mines extract materials like copper, silver, gold, zinc, iron, and coal, producing large amounts of waste called mine tailings.
• Mine tailings can be mixed with other materials to make tiles or masonry cement.

Cement Industries:

• Produce solid, liquid, and gaseous wastes.
• Solid wastes are used in construction or dumped in landfills.
• Liquid wastes (wash-offs) are treated to remove harmful substances and released into rivers, ponds, lakes, or seas.
• Gaseous wastes include flyash (fine, non-combustible ash particles), used for making bricks, concrete, and roofing sheets.

Oil Refineries:

• Produce poisonous gaseous and liquid wastes during crude oil refining.
• Gaseous wastes are cleaned using cleaners before release into the atmosphere.
• Liquid wastes are processed and safely dumped.

Construction Units:

• Generate waste stones, pebbles, broken bricks, and wood waste, mostly dumped in landfills, especially in large towns.

Agricultural Waste

Generated from cultivating soil, producing crops, and raising livestock.

Agricultural Residues:

• Plant parts left after extracting usable portions, often used as animal feed.

Bagasse:

• Plant residue (e.g., sugarcane) after juice extraction, used as firewood or in the paper industry.

Pesticides and Fertilizers:

• Collect in soil and wash into rivers and ponds through irrigation or rainwater, causing pollution.
• Strict precautions are needed during their use.

Animal Wastes:

• Includes cow dung and other faecal matter, used to make manure.

Municipal Waste

• Includes waste from households, public toilets, hospitals, hotels, restaurants, and offices, carried away through sewers as sewage.
• Sewage is divided into:
  • Degradable waste (can be broken down chemically into non-toxic parts).
  • Non-degradable waste (dumped or buried at safe locations).
• Septic tanks are used to degrade the degradable portion of sewage.

e-Waste

• Electronic waste (e-waste) includes discarded electrical and electronic equipment like old computers, TVs, refrigerators, radios, cell phones, batteries, fluorescent tubes, electronic toys, medical instruments, and lead-acid batteries.
• Contains harmful substances (lead, cadmium, mercury) and valuable materials (gold, silver, copper).
• Mainly generated in large cities, but smaller towns are also contributing due to improved living standards.
• Disposal:
  • Rag pickers and waste dealers extract usable components or secondary raw materials.
  • Burning printed wiring boards releases harmful fumes and residues, which may enter food chains and cause health issues like cancer.
• Recycling:
  • Most e-waste contains reusable materials like metals, but recycling must be done carefully under skilled supervision.
  • Special e-bins should be used for collecting e-waste, with municipal agencies arranging safe disposal.

Science Teaching & Research Laboratories Wastes

• Generated from teaching institutes and research labs, including broken glass apparatus, condemned machines, waste chemicals, and animal/plant wastes from biology labs.
• Disposed of in deep pits or burned in special enclosures.
• Radioactive waste (e.g., cobalt-60) requires special care to avoid health risks, as mishandling can harm humans.

Methods of Safe Disposal of Wastes

Various methods are used for safe waste disposal, including segregation, dumping, composting, drainage, effluent treatment, incineration, scrubbers, and electrostatic precipitators.

Segregation

Separating waste into three categories: reusable, degradable, and non-degradable.

Reusable Waste:

• Includes paper (newspapers, old books, exam answer sheets) that can be recycled.
• Metallic components are separated for reuse.

Degradable Waste:

• Organic waste (e.g., vegetable/fruit peelings) is decomposed into manure through biodegradation by microorganisms.

Non-Degradable Waste:

• Includes certain plastics, which are dumped in safe locations.

Dumping

Non-degradable waste is placed in specially dug pits away from human settlements.

Composting

Organic waste is decayed to produce manure for agricultural fields or gardens.

Method of Preparing Compost:

• Dig a trench (5 m long, 1.5 m wide, 1.5 m deep).
• Spread a 30 cm layer of mixed refuse and waste.
• Wet the layer with a mixture of cow dung and mud.
• Add more layers of refuse until the heap rises 0.5 m above ground level.
• Leave for 3 months, then rearrange into conical heaps covered with earth.
• After 50–60 days, the compost is ready for use in fields or gardens.

Town refuse compost (e.g., Okhla Khad in Delhi) is made from garbage and human sewage. Dry composting toilets are a hygienic, cost-effective solution for human waste disposal.

Drainage

A proper drainage system carries away fluid wastes (other than sewage) to prevent accumulation in pits or puddles, which can breed mosquitoes and harmful insects.

Treatment of Effluents Before Discharge

Industrial and municipal wastewater is treated in Effluent Treatment Plants before release into water bodies.

Treatment Stages:

• Primary Treatment: Removes large debris through sedimentation in tanks.
• Secondary Treatment: Wastewater is pumped into oxidation ponds, where microorganisms oxidize organic matter, producing CO₂ and sludge (used as manure).
• Tertiary Treatment: Removes dissolved chemicals, metals, or pathogens, allowing water to be discharged into natural waters or used for irrigation.

Incineration

Burning waste to reduce its volume, weight, and toxicity.

Purposes:

• Reduces waste volume.
• Reduces waste weight.
• Converts toxic waste into less toxic or non-toxic forms.

Impact:

• Releases fumes and harmful substances.

Precautions:

• Perform incineration at high temperatures.
• Use pollution control devices.
• Install incinerators away from residential areas.

Advantages:

• Residual ash occupies less landfill space.
• Bottom ash can be used to recover metals.
• Heat from incineration can generate electricity.

Scrubbers

• Devices that remove gaseous and particulate air pollutants by passing air through dry or wet packing material.
• Clean air is released, free of dust and certain gaseous pollutants dissolved in the wet packing.

Electrostatic Precipitators

• Remove particulate matter from dirty air by passing it through electrically charged plates.
• Charged particles are attracted to oppositely charged plates, allowing clean gas to pass through.
• Can remove up to 90% of particulate matter from thermal plants.

Points to Remember

• Waste is anything discarded as useless.
• Domestic waste includes kitchen leftovers, plastics, glass, rags, and paper.
• Old newspapers are a major reusable waste, often recycled.
• Liquid wastes from oil refineries are processed and dumped safely.
• Construction waste is often dumped in landfills near large cities.
• Metallic parts from domestic or industrial waste are separated for reuse.
• Agricultural waste (crop residue, bagasse, animal waste) is used as animal feed, in paper industries, or as manure.
• Municipal sewage includes discharges from homes and public utilities, treated in septic tanks for degradable portions.
• e-Waste includes discarded electronics, containing harmful (lead, mercury) and valuable (gold, copper) materials.
• Most e-waste can be recycled, but requires careful handling.
• Safe disposal methods include segregation, dumping, composting, and incineration.
• Composting converts organic waste into manure.
• Effluent treatment separates debris, decomposes organic matter into sludge, and removes chemicals before discharge.
• Incineration reduces waste volume, weight, and toxicity but requires precautions to avoid pollution.
• Scrubbers remove gaseous and particulate pollutants.
• Electrostatic precipitators attract particulate pollutants to charged plates for removal.