Environmental Pollution - 3 - Environment for UPSC CSE

What is Solid Waste?

Solid waste consists of unwanted or useless solid materials generated by human activities in residential, industrial, commercial, institutional and public areas. It includes everyday items such as household refuse, industrial by-products, construction debris and discarded materials from offices, shops and hospitals.

Solid waste may be classified in three common ways:

• By origin: domestic (household), industrial, commercial, construction and demolition, institutional and municipal street sweepings.
• By composition: organic (food, garden waste), glass, metal, plastic, paper, textiles, rubber and mixed inert matter.
• By hazard potential: non-hazardous, toxic, flammable, infectious, radioactive and other hazardous categories.

Effective solid waste management aims to reduce or eliminate adverse impacts on the environment and public health. Typical municipal processes include waste monitoring, segregation at source, collection, transport, processing (composting, recycling), energy recovery and scientific disposal. The amount and composition of waste vary with population density, urbanisation, economic activity and lifestyle: higher per capita income and consumer culture generally increase the quantum and proportion of non-biodegradable waste.

Plastic Waste

Plastics are light, versatile and inexpensive materials that revolutionised modern packaging and products in the 20th century. Their durability and convenience have also led to a pervasive "throw-away culture", making plastics a major environmental concern. Plastics resist biodegradation and can persist in the environment for decades.

Sources of plastic waste

• Households (packaging, carry bags, containers).
• Health and medical sectors (disposable syringes, packaging, tubing).
• Hotels, restaurants and catering (single-use cutlery, sachets).
• Air and rail travel (in-flight/ onboard disposables) and other transport sectors (packaging waste).
• Fishing and aquaculture (nets, lines, gear).

Environmental and health effects

• Plastic litter makes urban and rural landscapes unsightly and unhygienic and increases municipal cleaning costs.
• Some conventional plastics and their additives have been associated with reproductive and endocrine problems in wildlife and humans.
• Dioxins and furans, highly toxic and potentially carcinogenic compounds, can form when certain plastics (for example PVC) are manufactured or burned; these can bioaccumulate and may be passed to infants through breast milk.
• Open burning of plastics releases toxic gases and particulate matter, contributing to air pollution and health risks.
• Plastic carry bags and film can leach dyes and additives into food and water, causing contamination risks.
• Plastic wastes choke drains, reduce soil porosity, impair groundwater recharge and aggravate urban flooding by blocking stormwater systems.
• Terrestrial and aquatic animals often mistake plastic debris for food; ingestion causes internal injury, starvation and death.
• Plastics in compost or manure reduce soil quality and may remain in soil for many years, affecting soil microbe activity and fertility.
• Designing and adopting eco-friendly, biodegradable plastics and promoting source reduction, reuse and recycling are priority needs.

Types of Solid Waste

Solid wastes are commonly grouped for planning and regulatory purposes:

• Municipal solid waste: household refuse, street sweepings, market wastes, construction and demolition debris and sanitation residue.
• Hazardous waste: industrial and certain household wastes that are toxic, corrosive, flammable or reactive.
• Biomedical (hospital) waste: infectious, pathological and sharps waste from health-care facilities and laboratories.

Municipal waste

• Municipal solid waste comprises domestic waste, construction and demolition debris, market and street waste, and sanitation residues.
• Urbanisation, changing consumption patterns and packaged goods have increased municipal waste volumes and the share of non-biodegradable materials.
• Historical figures indicate rapid growth: in 1947 Indian cities and towns generated an estimated 6 million tonnes of solid waste annually; by 1997 the estimate was about 48 million tonnes.
• More than a quarter of municipal solid waste may not be collected in many urban areas. Around 70% of Indian cities (as cited in older assessments) lacked adequate transportation capacity for refuse collection, and many landfills were neither engineered nor lined to prevent soil and groundwater contamination.
• Increasing use of cans, aluminium foils, plastics and other non-biodegradable packaging raises long-term waste-management challenges.

Hazardous waste

• Hazardous waste contains chemicals or properties that may be harmful to humans, animals or the environment: e.g., heavy metals, cyanides, organic solvents, acids and oxidisers.
• India generates an estimated around 7 million tonnes of hazardous wastes yearly, with significant concentrations in states with heavy industry (historically noted: Andhra Pradesh, Bihar, Uttar Pradesh and Tamil Nadu).
• Household items that may be classified as hazardous include old batteries, solvent-containing products, paints, pesticides and expired medicines.
• Major industrial sources include metal processing, chemicals, pesticides, dyes, refineries and rubber goods manufacture.
• Direct exposure to hazardous chemicals such as mercury and cyanide can be acutely toxic or fatal; long-term exposure may cause chronic diseases.

Hospital (biomedical) waste

• Biomedical waste arises during diagnosis, treatment, immunisation, research or production/testing of biologicals. It includes soiled waste, discarded medicines, sharps (needles, syringes), bandages, body fluids, anatomical wastes, cultures and laboratory reagents.
• Chemicals used in health facilities include disinfectants (formaldehyde, phenols) and mercury in some equipment.
• Improper handling of biomedical waste poses a serious infectious risk to health workers, waste handlers and the public.
• Surveys have shown many health-care establishments historically did not give sufficient attention to safe biomedical waste management. After the notification of the Bio-medical Waste (Management and Handling) Rules, 1998, practices of segregation, collection, treatment and disposal have been progressively improved.

Treatment and Disposal of Solid Waste

Open dumps

Open dumps are unmanaged sites where mixed waste is deposited without segregation, covering or treatment. They become breeding grounds for vectors (flies, rats), cause odour problems and contaminate surface water and groundwater via run-off and leachate. Open dumping is an unsanitary practice that should be phased out in favour of engineered solutions.

Landfills

Traditional landfills are pits where refuse is deposited and covered with soil periodically to reduce odour and vector access. When properly operated and closed, the land may be reclaimed for parks or other uses.

Problems: Conventional landfills often receive mixed waste, and rainwater percolating through the waste generates leachate-a contaminated liquid that can pollute surrounding soil and groundwater.

Sanitary landfills

Sanitary landfills are engineered facilities that minimise leachate and gas emissions. They use liners (clay or impermeable synthetic membranes), leachate collection systems and cover layers, and they are sited over relatively impermeable subsoils. Sanitary landfills are far more protective but are capital-intensive to construct and operate.

Incineration

Incineration burns waste at high temperature in controlled furnaces to reduce waste volume and produce ash. When recyclables are removed first, incineration can reduce the quantity of material requiring disposal; modern facilities can recover energy from the combustion process.

However, incineration generates toxic ash and air emissions (dioxins, furans, particulate matter) if not properly controlled. It is generally used for volume reduction and to treat infectious or hazardous wastes and is typically a last resort where recovery and recycling are not feasible.

Pyrolysis

Pyrolysis is thermal decomposition of organic material in the absence (or limited presence) of oxygen. It produces gaseous and liquid products (syngas, oils) and char that can be used as fuels or feedstock. Pyrolysis is an alternative to open burning and incineration, and can be applied to carbonaceous wastes (agricultural residues, wood, shells, husk) to produce charcoal, tars and fuel gases.

Composting

• Composting is an aerobic biological process in which microorganisms (bacteria and fungi) decompose biodegradable organic waste into a humus-like material called compost.
• Finished compost is rich in organic matter and nutrients and improves soil structure, water-holding capacity and fertility.
• Composting recycles nutrients to soils, reduces the volume of biodegradable garbage and is a low-cost, environmentally sound treatment for organic waste.

Vermiculture (vermicomposting)

Vermiculture, or earthworm farming, supplements composting by adding earthworms that consume organic waste and produce nutrient-rich worm castings (vermicompost). Vermicompost is an excellent soil amendment and accelerates organic waste conversion.

Four Rs of waste management

• Reduce: minimise the generation of waste through changed consumption patterns and product design.
• Reuse: use items multiple times before disposal.
• Recycle: recover materials (paper, glass, metals, certain plastics) to manufacture new products.
• Recover (or energy recovery): recover energy from waste where recycling is not feasible (e.g., controlled combustion with energy capture).

Waste Minimisation Circles (WMC)

• WMCs are collaborative groups, often among small and medium industrial units in a cluster, working together to minimise waste generation and improve resource efficiency.
• The World Bank and national agencies have supported such industrial cluster initiatives with technical and financial assistance, while the central environmental ministry typically acts as a nodal authority.
• These initiatives align with policy statements such as the Policy Statement for Abatement of Pollution, 1992, which emphasises public education on environmental risks, the economic costs of resource degradation and the role of citizens and NGOs in environmental monitoring.

Thermal Pollution

Thermal pollution is the rise or fall in temperature of a natural aquatic environment caused by human activities. It commonly occurs when industries and power plants use water for cooling and then discharge heated water into rivers, lakes or coastal zones, or when cold water releases from reservoirs lower downstream temperatures. Deforestation of riparian zones can also increase water temperatures by increasing solar heating.

Major sources

• Thermal effluents from fossil-fuel and nuclear power plants.
• Industrial cooling water discharge.
• Deforestation and removal of streamside vegetation (reducing shade).
• Soil erosion and sedimentation that alter water clarity and thermal properties.

Ecological effects - warm water

Temperature changes affect aquatic organisms primarily by reducing dissolved oxygen and altering ecosystem composition.

• Warm water holds less dissolved oxygen (DO), reducing oxygen availability for fish and aerobic microorganisms.
• Higher temperatures increase metabolic rates of aquatic animals, raising food requirements and potentially causing food shortages and population declines.
• Species composition shifts: some organisms migrate away, others that tolerate higher temperatures may invade, changing food webs and reducing biodiversity.
• Even a change of 1-2 °C can alter organism metabolism, enzyme function and cell permeability, affecting survival and reproduction.
• Increased plant and algal growth (blooms) can occur; these blooms may later deplete oxygen (similar to eutrophication), causing fish kills.

Ecological effects - cold water

Cold water releases from reservoir bottoms can lower downstream temperatures, harming fish species adapted to warmer conditions and affecting egg and larval development of many aquatic organisms.

Control measures

• Use cooling towers or cooling ponds to lower effluent temperature by evaporation before discharge.
• Design or retrofit plants to improve thermal efficiency so less waste heat is produced.
• Cogeneration: use waste heat from electricity generation for industrial processes or district heating to reduce thermal discharges.
• Retain riparian vegetation and buffer strips to shade streams and reduce solar heating.
• Prevent erosion and sedimentation to maintain water clarity and thermal stability.

Plastic Pollution (Marine and Terrestrial)

Marine ecosystems cover about 70% of the Earth's surface and support a large share of global biodiversity and primary production. Plastics have become a pervasive contaminant in marine and coastal environments and pose a threat to plankton, fish, seabirds, turtles and benthic communities, and thereby to fisheries and human food security.

Plastics in the marine environment

• Quantitative estimates of annual plastic input into the oceans vary and depend on land-based sources, riverine transport and sea-based sources (fishing, shipping). Much plastic pollution originates from fisheries and from beach litter transported to the sea.
• Plastics floating or submerged in seawater degrade by UV-driven photo-oxidation much more slowly than on land, extending their environmental lifetime.
• Once plastics enter the ocean, retrieval, sorting and recycling are far more difficult than on land, so they tend to accumulate and fragment into microplastics.
• Fragmentation produces microparticles that can be ingested by planktonic organisms and benthic fauna, potentially entering food chains.

Impact of microparticles

• Zooplankton (for example Antarctic krill) and other small filter feeders readily ingest plastic particles on the order of tens of micrometres, often without discrimination from food particles.
• Plastics are largely bio-inert, but physical obstruction, reduced feeding efficiency and indirect physiological effects (satiation on indigestible material) have been observed.
• Plastics concentrate hydrophobic organic contaminants from seawater (PCBs, DDT, nonylphenols), which have high partition coefficients. These adsorbed pollutants may be transferred through the food web when plastics are ingested.
• More than 250 species worldwide have documented impacts from plastics, though most attention has been on surface and coastal species while impacts on benthic communities remain less studied.
• Research on plastics in the marine environment has increased, but government agencies and industry responses have been limited relative to the scale of the problem.

Plastics in the land environment

• Uncollected plastic waste clogs drains and stormwater systems, contributing to urban flooding and creating unhygienic conditions that favour water-borne diseases.
• Animals ingesting plastic litter may suffer illness or death.
• Non-biodegradable plastics in soil reduce infiltration and can impede groundwater recharge.
• Additives in plastics (plasticisers, flame retardants, pigments) may leach and contaminate groundwater or soils with long-term health implications.

Bioremediation

Bioremediation uses biological agents-microorganisms such as bacteria and fungi, or plants-to transform or remove environmental contaminants into less toxic forms. Microorganisms used may be native to a contaminated site or introduced from elsewhere to augment pollutant degradation.

Monitoring bioremediation typically involves measuring redox potential, pH, temperature, oxygen concentration, electron acceptor/donor levels and concentrations of breakdown products (for example carbon dioxide for aerobic degradation).

Bioremediation strategies

In situ techniques

These treat contamination without excavation, directly at the site.

• Bioventing: supply air and nutrients via wells to contaminated soils to stimulate indigenous aerobic bacteria; commonly used for simple hydrocarbon contamination.
• Biosparging: inject air below the water table to increase dissolved oxygen in groundwater and enhance aerobic biodegradation.
• Bioaugmentation: add specific strains of microorganisms to accelerate breakdown where indigenous populations are insufficient.

Ex situ techniques

These require removal of contaminated material for treatment elsewhere.

• Landfarming: excavated soil is spread over beds and periodically tilled to encourage aerobic degradation by native microbes.
• Biopiles: engineered, aerated piles combining landfarming and composting features to treat hydrocarbon-contaminated soils.
• Bioreactors: enclosed systems where contaminated soils, sediments or water are processed under controlled biological conditions to enhance degradation.
• Composting: as described earlier, can be used for suitable organic wastes.

Practical applications include the development of microbial consortia such as the mix known as "Oilzapper" (developed by TERI), designed to biodegrade oil-contaminated sites efficiently and leave minimal harmful residues. Bioremediation is often cost-effective and environmentally preferable to physical or chemical remediation, but it is limited to biodegradable compounds and may require longer timeframes.

Genetic engineering approaches

Genetic engineering can enhance bioremediation by modifying microorganisms to degrade specific pollutants more rapidly or to tolerate harsh environmental conditions. Engineered strains are used cautiously, subject to regulatory and ecological safety considerations.

Phytoremediation

Phytoremediation employs plants to remove, stabilise or degrade contaminants in soil and water. It is a green, low-cost remediation option suited for large, diffuse contamination and for sites where excavation is impractical.

Types of phytoremediation

• Phytoextraction (phytoaccumulation): plants take up contaminants (often heavy metals) into roots, shoots and leaves, which can later be harvested and managed.
• Phytotransformation (phytodegradation): plants take up organic contaminants and metabolise them into less toxic compounds via plant enzymes.
• Phytostabilization: plants immobilise contaminants in the root zone, reducing mobility and erosion-related spread.
• Rhizodegradation (phytodegradation in the rhizosphere): root exudates stimulate microbial communities that degrade organic pollutants in the soil.
• Rhizofiltration: plant roots absorb contaminants from water, useful for treating contaminated surface waters, ponds and wetlands.

Examples of engineered bioremediation include the bacterium Deinococcus radiodurans being investigated for detoxifying toluene and ionic mercury from certain radioactive wastes, demonstrating the potential of microbes in specialised remediation tasks.

Mycoremediation and mycofiltration

• Mycoremediation: use of fungi to degrade, accumulate or transform pollutants. Fungi produce powerful extracellular enzymes capable of breaking down complex organic contaminants.
• Mycofiltration: use of fungal mycelia as a filtration medium to trap, immobilise and partially degrade pathogens and toxic compounds in water and soil run-off.

Advantages and limitations of bioremediation

• Advantages: effective for a wide range of biodegradable contaminants; can achieve destruction rather than transfer; generally less expensive and more environmentally friendly than many physical/chemical treatments.
• Limitations: only applicable to biodegradable compounds; biological processes can be specific to certain pollutants and environmental conditions; scaling from laboratory or pilot studies to full field operations can be challenging; treatment times may be longer than for some alternative technologies.

Environmental Pollution and Health

Understanding pollution and health impacts requires combining emissions data with exposure assessment and health outcomes. Policy and control priorities should therefore focus not only on which sources emit the most but on which sources cause the greatest human exposure to health-damaging pollutants.

First: Source apportionment and exposure

• Pollution inventories and source apportionment studies identify the relative contributions of different sources, but they should be interpreted within a coherent framework that links emissions to population exposure and health risk.
• Globally, road transport contributes a substantial share of particulate pollution in urban areas-studies indicate vehicle emissions can account for about a quarter to nearly half of particulate concentrations in many cities.

Second: Microenvironmental exposure

• People are not exposed only to ambient (background) pollutant concentrations; microenvironmental exposures (near roads, in workplaces, indoors) can be much higher.
• It has been observed that with each breath an individual may inhale several times the ambient concentration due to proximity to sources and short-term peaks; vehicular fumes produce the highest exposures near roads-often up to a few hundred metres from major traffic corridors.

Third: Mixtures and multi-pollutant regulation

• People are exposed to complex mixtures of pollutants (particulate matter, nitrogen oxides, ozone, volatile organic compounds and air toxics). The combined health effect can be greater than that of any single pollutant.
• Targeting multi-pollutant sources (for example diesel emissions) produces greater public-health benefits because it reduces exposure to several harmful agents simultaneously; diesel exhaust has been classified as a carcinogen for its link to lung cancer.

Fourth: Linking air quality policy to health care needs

• Air quality management has often operated separately from public-health planning; better integration is required to address the rising burden of chronic diseases influenced by air pollution.
• India and many other countries are experiencing a health transition with chronic diseases (cardiovascular disease, cancer, chronic respiratory disease and stroke) accounting for a large portion of deaths and disability; these conditions are strongly influenced by air pollution and other environmental exposures.

Conclusion (optional summary): Solid-waste and plastic pollution, thermal pollution, and chemical contamination pose significant environmental and public-health challenges. Integrated approaches-source reduction, segregation, recycling, engineered disposal, biological remediation and careful regulation of hazardous wastes-are necessary to protect ecosystems and human health. Policies that combine technical solutions with public education, industry responsibility and community participation yield the best long-term outcomes.