Dead Zones and Bioremediation

• Dead zones are biological deserts or hypoxic zones in the ocean with very low oxygen concentration (hypoxic conditions).
• Dead zones emerge when the influx of excess chemical nutrients spurs algae growth or algal blooms.
• Dead zones usually occur 200-800 meters below the surface, in the saltwater layer.
• Hypoxic zones can occur naturally due to the upwelling of excess nutrients.
• Human activity can quicken the formation of dead zones.
• Dead zones are detrimental to animal life.
• Most of the animal life either dies or migrates from the zone.

Bioremediation

• Bioremediation uses microorganisms (bacteria and fungi) to degrade environmental contaminants into less toxic forms.
• Microorganisms can be specifically designed for bioremediation using genetic engineering techniques.

In situ bioremediation

• In situ bioremediation occurs at the site of contamination.
• Bioventing supplies nutrients through wells to contaminated soil, stimulating bacteria growth.
• Biosparging involves injecting air under pressure below the water table to increase groundwater oxygen concentrations, enhancing biological degradation of contaminants by bacteria.
• Bioaugmentation introduces microorganisms to a contaminated site, enhancing the degradation process.

Ex-situ bioremediation

• Ex-situ bioremediation involves removing the contaminated material for treatment elsewhere.
• Land farming entails excavating contaminated soil and spreading it over a prepared bed, periodically tilling it until pollutants are degraded.
• The goal of land farming is to stimulate indigenous biodegradative microorganisms and facilitate their aerobic degradation of contaminants.
• Bioreactors process contaminated solid material (soil, sediment, sludge) or water through an engineered containment system.
• Composting is nature's recycling of decomposed organic materials into a rich soil known as compost.

Air Pollutants

• Air pollution refers to undesirable changes in the physical and chemical constituents of air due to human activities.

Sources

• Primary pollutants are directly released into the atmosphere.
• Secondary pollutants result from reactions with atmospheric pollutants.

Mode of Release

• Indoor pollutants come from cooking, smoking, air conditioning, etc.
• Outdoor pollutants come from industrial processes and transportation.

Chemical Composition

• Particulate matter can be solid or liquid aerosols.
• Gaseous pollutants mix with air in vapor form.

Basis of Persistence

• Primary pollutants persist in their original form when added to the environment.
• Secondary pollutants are formed by interactions among primary pollutants.

Basis of Existence in Nature

• Quantitative pollutants occur naturally but become pollutants when concentrations exceed a threshold level.
• Qualitative pollutants are man-made and don't occur in nature.

Basis of Biodegradability

• Biodegradable pollutants are waste products degraded by natural microbial action.
• Non-biodegradable pollutants don't decompose naturally or decompose slowly.

Basis of Origin

• Natural pollutants are released during natural processes.
• Anthropogenic pollutants are released during human activities.

Natural Sources of Air Pollution

• Includes ash from erupting volcanoes, dust from storms, forest fires, and pollen grains from flowers.

Human Sources of Air Pollution

• Power stations using coal/crude oil, furnaces, steam engines, internal combustion engines, household fuels, sewers, pesticide residues, agriculture, waste treatment, biomass burning.

Particulate Pollutants

• Particulate pollutants involve matter suspended in the air like dust and soot.
• Major sources of suspended particulate matter (SPM) include industries, vehicles, power plants, construction activities, oil refineries, railway yards, and marketplaces.
• PM10 are inhalable particles, generally 10 micrometers or smaller, from sources like construction, pollen, and emissions.
• PM2.5 are fine inhalable particles, generally 2.5 micrometers or smaller, often from combustion processes.
• Fly ash is an end product of coal combustion during power generation.
• Fly ash consists of silica, alumina, oxides of iron, calcium, magnesium, and toxic heavy metals.
• Fly ash is used in manufacturing cement, bricks, tiles, road embankment construction, etc.
• ASH TRACK Mobile App was launched by the Ministry of Power for better management of fly ash.
• ASH TRACK Mobile App provides an interface between fly ash producers and potential users.

Fluorides

• Fluorides come from aluminum, steel, electrochemical plants, blast furnaces, brick kilns, coal combustion, and glass etching factories.
• Volcanoes also release fluorides as gas or particulate pollutants.
• Fluoride particles settle on vegetation, burning leaf tips, leading to fluorosis in cattle, causing tooth loss, weight loss, and lameness.

Water Pollutants

• Pathogens in sewage, human/animal wastes, and runoff deplete dissolved oxygen and cause waterborne diseases.
• Organic pollutants like oil, grease, pesticides, plastics, and detergents disrupt marine life and can have toxic effects.
• Inorganic pollutants like fertilizers cause algal blooms, eutrophication, and can cause methemoglobinemia from nitrates.
• Acids and alkalies from mine drainage and industrial wastes kill freshwater organisms.
• Radioactive materials cause cancer and genetic defects.
• Heat decreases oxygen solubility.
• Sediments affect water quality and fish populations.

Water Pollution: Control Measures

• Treatment of wastewater before discharge involves sedimentation, coagulation, and filtration as primary treatment.

Primary Treatment

• Sedimentation allows silt, clay, and other matter to settle.
• Coagulation combines fine particles and colloidal suspensions into larger particles using chemicals like potash alum.
• Filtration removes suspended particles, flocculants, bacteria, and organisms through sand or fibrous materials.
• Sludge collected is used as fertilizer.

Secondary Treatment

• Softening removes undesirable calcium and magnesium cations from hard waters.
• Aeration exposes soft water to air, adding oxygen and encouraging bacterial decomposition of organic matter.

Tertiary Treatment

• Chlorine is a commonly used disinfectant.
• Other disinfection methods include ultraviolet radiation, ozone gas treatment, or reverse osmosis.

Oil Spills

• Skimmers physically retrieve oil, separating it from water.
• Sorbents absorb oil from the surface.
• Chemical surfactants can associate oil into smaller particles and accelerate dispersion.
• Bioremediation uses microorganisms to speed up natural biodegradation.

Heavy Metals

• Heavy metals ions found in water include Copper, Zinc, Silver, Chromium, Arsenic, Mercury, Cadmium, and Lead.

Agricultural Sources of Water Pollution

• Fertilizers containing nitrogen, phosphorus, and potassium.
• Pesticides containing chlorinated hydrocarbons organophosphates, metallic salts, carbonates, thiocarbonates, derivatives of acetic acid.
• Animal excreta.
• Excess nitrate in drinking water reacts with hemoglobin to form non-functional methaemoglobin, impairing oxygen transport.
• High nitrate levels may form carcinogens and accelerate eutrophication.

Thermal Pollution

• Thermal pollution occurs from thermal power plants and nuclear plants releasing hot water, decreasing dissolved oxygen.

Marine Pollution

• Marine pollution includes coastal city sewage, garbage disposal, navigational discharge of oil, detergents, and radioactive waste.
• Oil spills are uncontrolled releases of crude oil, gasoline, or other oil products into the atmosphere.
• Oil spills can contaminate land, air, or water.
• Oil spills are a major environmental problem, due to petroleum exploration, production on continental shelves, and transport of large amounts of oils in vessels.
• Oil spills are harmful to aquatic life, preventing sunlight penetration and reducing dissolved oxygen.
• Oil contains many toxic compounds that can cause health problems and death.

Methods to Clear Oil Spills

• Oil booms use floating barriers to stop spreading oil, which could be retrieved.

Community Waste Water

• Community wastewater includes discharges from houses, commercial and industrial establishments connected to a sewerage system.
• Community wastewater consists of human and animal excreta, food residues, cleaning agents, detergents, and other wastes.

Industrial Waste

• Industrial waste discharges several inorganic and organic pollutants.