Dead Zones and Bioremediation

Dead Zones

• Dead zones, also known as biological deserts or hypoxic zones, are ocean areas with very low oxygen concentration, referred to as hypoxic conditions.
• They occur when excess chemical nutrients trigger algal blooms.
• These 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.
• Dead zones are detrimental to animal life, and most of the animal life either dies or migrates.
• Human activity can create or enhance dead zones.

Bioremediation

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

In Situ Bioremediation

• In situ bioremediation takes place at the contaminated site.
• Bioventing supplies nutrients through wells to contaminated soil to stimulate bacteria growth.
• Biosparging involves injecting air under pressure below the water table to increase groundwater oxygen and enhance contaminant degradation by bacteria.
• Bioaugmentation involves importing microorganisms to a contaminated site to enhance degradation.

Ex Situ Bioremediation

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

Air Pollutants

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

Source of Air Pollutants

• Primary pollutants result from direct emission into the atmosphere (e.g., CO, SO₂, NOX, PM).
• Secondary pollutants result from reactions with atmospheric pollutants (e.g., Ozone, PAN).

Mode of Release

• Indoor pollutants come from cooking, smoking, air conditioning (e.g., CO, CO₂, VOCs).
• Outdoor pollutants come from industrial processes and transportation (e.g., PM, CO, VOCs).

Chemical Composition

• Particulate matter can be solid or liquid aerosols (e.g., PM2.5, PM10).
• Gaseous pollutants mix with air in vapor form (e.g., SOx, Ozone, NOx, CO).

Persistence

• Primary pollutants persist in their original form after being added to the environment (e.g., DDT, plastic).
• Secondary pollutants are formed by interactions among primary pollutants. An example is Peroxyacetyl Nitrate (PAN), formed by the interaction of nitrogen oxides and hydrocarbons.

Existence in Nature

• Quantitative pollutants occur in nature and become pollutants beyond a threshold level (e.g., Carbon Dioxide, Nitrogen Oxide).
• Qualitative pollutants are man-made and do not occur in nature (e.g., Fungicides, herbicides, DDT).

Biodegradability

• Biodegradable pollutants are waste products degraded by natural microbial action (e.g., sewage).
• Non-biodegradable pollutants do not decompose naturally or decompose slowly (e.g., plastics, polythene bags, DDT etc.).

Origin

• Natural pollutants are released during natural processes like volcanic eruptions and forest fires.
• Anthropogenic pollutants are released during human activities such as CO₂ emissions from burning fossil fuels.

Sources of Air Pollution

Natural Sources

• Ash from burning volcanoes.
• Dust from storms.
• Forest fires.
• Pollen grains from flowers in the air.

Human Sources

• Power stations using coal or crude oil release CO₂.
• Furnaces using coal, cattle dung cakes, firewood, kerosene.
• Steam engines in railways, steamers, motor vehicles give out CO₂.
• Motor and internal combustion engines running on petrol, diesel, kerosene.
• Vegetable oils, kerosene, and coal as household fuels.
• Sewers and domestic drains emanating foul gases.
• Emissions from agriculture, waste treatment, and biomass burning (stubble burning).

Particulate Pollutants

• Particulate pollutants are 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, with diameters generally 10 micrometers and smaller, coming from construction sites, pollen, or vehicle/industrial emissions.
• PM2.5 are fine inhalable particles, with diameters generally 2.5 micrometers and smaller, often from combustion processes.
• PM2.5 particles can penetrate deep into lungs and bloodstream, causing more severe health issues.

Fly Ash

• Fly ash is an end product of combustion during power generation in coal-based thermal power plants.
• It comprises silica, alumina, oxides of iron, calcium, magnesium, and toxic heavy metals.
• Uses of Fly Ash: manufacturing of Portland Cement, bricks/blocks/tiles, road embankment construction.
• ASH TRACK Mobile App was launched by the Ministry of Power for better management of fly ash, providing an interface between producers and users.

Fluorides

• Sources of fluorides: aluminum, steel, electrochemical plants, brick kilns, coal combustion, and glass etching factories.
• Volcanoes also release fluorides as gaseous and particulate pollutants.
• Fluoride particles settle on vegetation, burn tips of leaves, and cause fluorosis in cattle, resulting in loss of teeth, weight, and lameness.

Water Pollutants

Pathogens:

• Sources: Sewage, human and animal wastes, natural and urban runoff from land, industrial waste.
• Effects: Depletion of dissolved oxygen; foul odor; health effects (waterborne diseases).

Organic Pollutants:

• Sources: Automobile and machine waste, tanker spills, agricultural chemicals, industrial and household waste.
• Effects: Disruption of marine life, aesthetic damage, toxic effects, possible genetic defects and cancer.

Inorganic Pollutants:

• Sources: Agricultural runoff, mine drainage, industrial wastes, and urban runoff.
• Effects: Eutrophication, aesthetics, algal bloom, methemoglobinemia, and unfit water for use.

Radioactive Materials:

• Sources: Natural sources, uranium mining and processing, hospitals, and research labs.
• Effects: Cancer and genetic defects.

Heat:

• Source: Cooling water from industrial, nuclear, and thermal plants.
• Effects: Decreased solubility of oxygen and disrupted aquatic ecosystems.

Sediments:

• Source: Natural erosion, runoff from agricultural and construction sites.
• Effects: affects water quality and reduces fish populations.

Water Pollution Control Measures

• When wastewater is dumped into a river or stream, treatment involves sedimentation, coagulation, and filtration.
• This is primarily treatment.
• Water required for drinking undergoes secondary and tertiary treatments.

Primary Treatment

• Sedimentation allows pollutants to settle and move out.
• Coagulation combines fine particles and colloidal suspensions.
• Filtration filters suspended particles, flocculants, bacteria, and organisms.
• Total impurities collected are called sludge, and are used as fertilizer.

Secondary treatment

• Undesirable calcium and magnesium cations are removed.
• Soft water is exposed to air by forcing air through it for oxygen.
• This encourages bacterial decomposition of organic matter.
• Oxygen addition reduces carbon dioxide and sulfide.

Tertiary treatment

• Chlorine is used to kill bacteria.
• Other methods of disinfection are also used.

Oil Spill Cleanup

• Skimmers physically remove oil by separating it from the water.
• Sorbents absorb oil from the surface.
• Chemical surfactants can associate oil into smaller particles to accelerate their dispersion.
• Bioremediation agents such as microorganisms, like Paraperlucidibaca, Thalassolituus, can speed up natural biodegradation and help remove several classes of contaminants.

Heavy Metal Ions in Water

• Copper: fertilizers, tanning, and photovoltaic cells.
• Zinc: soldering, cosmetics, and pigments.
• Silver: refining of copper, gold, nickel, zinc, jewelry, and electroplating industries.
• Chromium: leather industry, tanning, and chrome plating industries.
• Arsenic: wooden electricity poles treated with arsenic, pesticides, fertilizers, oxidation of pyrite and arsenopyrite.
• Mercury: combustion of coal, municipal solid waste incineration, and volcanic emissions.
• Cadmium: paints, pigments, electroplated parts, batteries, plastics, rubber, photoconductors, and photovoltaics.
• Lead: PVC pipes, recycled PVC, lead paints, jewelry, lead batteries, and lunch boxes.

Agricultural Sources of Pollution

• Fertilizers consist of nitrogen, phosphorus, and potassium.
• Pesticides consist of chlorinated hydrocarbons, organophosphates, metallic salts, carbonates, and derivatives of acetic acid.
• Animal excreta, such as dung.
• Excess nitrate in drinking water reacts with hemoglobin to form non-functional methaemoglobin and impairs oxygen transport, called methemoglobinemia or blue baby syndrome.

Thermal Pollution

• Comes from thermal power plants and nuclear plants that release hot waters, decreasing dissolved oxygen in water.

Marine Pollution

• Includes coastal city sewage and garbage disposal and navigational discharge of oil, detergents, and radioactive waste.

Oil Spills

• Oil spills involve the uncontrolled release of crude oil, gasoline, fuel, or other oil byproducts into the atmosphere or water.
• They are a major environmental problem, chiefly from petroleum exploration and production intensified on continental shelves.
• Oil spills harm aquatic life by preventing sunlight from penetrating the surface and reducing dissolved oxygen.
• Oil toxicity comes from toxic compounds that can cause serious health problems, like heart damage, stunted growth, immune system effects, and even death.
• To clean up oil spills, oil booms (floating barriers) are used to stop the spreading of oil, which can then be retrieved.

Sources of Water Pollution

• Community wastewater includes discharges from houses, commercial, and industrial establishments and consists of human and animal excreta, food residues, cleaning agents, detergents, and other wastes.
• Industrial waste includes discharges of several inorganic and organic pollutants.

Types of Industries and Their Pollutants

• Mining: Chlorides, various metals, ferrous sulphate, sulphuric acid, hydrogen sulphide, ferric hydroxide, surface wash offs, suspended solids, chlorides, and heavy metals.
• Iron and Steel: Suspended solids, iron cyanide, thiocyanate, sulphides, oxides of copper, chromium, cadmium, and mercury; releases oil, phenol, and naphtha.
• Chemical Plants: various acids and alkalies, chlorides, sulphates, nitrates of metals, phosphorus, fluorine, silica, and suspended particles; releases aromatic compounds solvents, organic acids, and nitro compound dyes.
• Pharmaceutical: Releases proteins, carbohydrates, organic solvent intermediate products, drugs, and antibiotics.
• Soap and Detergent: Releases tertiary ammonium compounds and alkalies.
• Food processing: Releases highly putrescible organic matter and pathogens.
• Paper and Pulp: Releases sulphides and bleaching liquors, cellulose fibers, bark, wood sugars organic acids.

Types of Pollution

• The nature of pollution refers to any undesirable alteration in the physical, chemical, or biological attributes of air, land, water, or soil.
• Types of pollution include air pollution, noise pollution, water pollution, soil pollution, radioactive pollution, light pollution, or nitrogen pollution.

Water Pollution

• Water pollution is the presence of undesirable substances or pollutants in the water, such as organic, inorganic, biological, radiological, or heat, which degrade water quality so that it becomes unfit for use.

Sources

• Point sources are from a single, identifiable location.
• Non-point sources are from diffuse sources, including agricultural runoff, urban runoff, industrial waste water, and atmospheric deposition.
• Natural sources of water pollution include soil erosion and the leaching of minerals from rocks (due to natural solubility and solubility triggered by acid rain) and the decaying of organic matter.