Environmental Science Chapter on Air Pollution

Wastewater Treatment

• Wastewater is water used in a process that is then discharged for disposal.
• Wastewater can come from domestic sewage or industrial sources (effluent).
• Wastewater is treated to avoid harming the environment and to preserve water resources.
• Treated wastewater can be reused and this decreases the water footprint of a product, increasing product value.
• Water costs are increasing, making treated wastewater reuse important for profitability.
• Water availability is a major issue in many cities, with irregular supplies.
• Water quality control is absent in many tanker water supplies, making water unsafe
• Poor water quality leads to mass migration and water scarcity

Water Quality

• Drinking water standards are different from wastewater quality levels.
• Sewage wastewater parameters can vary regionally based on pollution control board policy.
• For domestic wastewater, common parameters like pH, TSS, BOD, COD and O&G are stipulated, with example values varying depending on regional norms.
• Important parameters for industrial wastewater are process-specific.

Wastewater Treatment Processes

• Wastewater treatment planning depends on contaminant type.
• Inorganics are treated based on their nature and reactivity.
• Organic contaminants are typically removed through biological methods, sometimes combined with other processes.
• Common wastewater treatment stages include primary (screening, grit removal, pH correction, oil removal, settling), secondary (activated sludge process), and tertiary (filtration, chlorination).

Wastewater Treatment Processes - Primary

• Screening: Removal of coarse solid material
• Grit Removal: Removal of sand/silt
• pH Correction: Adjustment to make pH suitable
• Oil Removal: Removal of oil
• Primary Settling: Removal of Suspended Solids

Wastewater Treatment Processes - Secondary

• Activated Sludge Process: Most common biological method for organic removal in wastewater
• Aerobic Digestion + Anaerobic Digestion: (Additional secondary processes if required)

Wastewater Treatment - Components of ASP

• Bioreactor: For organic degradation
• Surface Aerators: To provide oxygen
• Settler-Clarifier: For separating solids from liquid
• Sludge Recirculation: To maintain consistent microbial concentration in the bioreactor
• Excess sludge wastage: To dewater sludge, typically via SDB/Centrifugal3

Wastewater Treatment - Components of MBBR

• Media: (Plastic media to support high microbial biomass)
• Bioreactor: For supporting bio-reaction
• Air Diffusers/Blowers: Providing oxygen for bacteria
• Settler: Removing solids from the wastewater flow
• Sludge Recirculation: To maintain consistency in the process.

Wastewater Treatment - SBR Process

• Bio-Reactor: For treating the wastewater
• Grit Chamber: Removing large solids
• Air Blower: Provides oxygen
• Chlorination: Kills any remaining microorganisms
• Filter Feed Tank: Treating the wastewater further and ensuring no biomass is passed out via disinfection

Wastewater Treatment - MBR Process

• Membrane Bioreactor (MBR): Combines biological and membrane processes
• In-situ configuration: UF membrane is inside the bioreactor
• Ex-situ configuration: UF membrane is outside of the bioreactor
• Anoxious chamber: Smaller with 20% of volume provided (for biomass suspension)
• Aerobic chamber: For degrading organics

Wastewater Treatment - Disposal

• Land Disposal: Treated waste is used as fertilizer
• Deep Well Injection: Introducing treated waste into deep wells
• Encapsulation: Immobilizing hazardous substances, such as placing them in suitable containers.
• Ocean Dumping: Disposal into the ocean. This method is not recommended due to the large scale of potential pollution risk

3R's of Waste Management

• Source Reduction: Reducing raw materials use and minimizing packaging.
• Reuse: Returning previously used items to reuse in other processes / products.
• Recycling: Processing waste materials to create new products.

Wastewater Treatment - Advantages & Disadvantages

• Advantages: Reducing water use, product cost, environmental protection and profitability
• Disadvantages: Costs, water availability issues and possible operational problems.

Wastewater Treatment - Other aspects

• Contaminants can be organic or inorganic
• Legal requirements for wastewater treatment ensure its safety.
• Different regions have different standards for regulating wastewater

Other

• Methods for controlling automotive emissions: Modify internal combustion engines, develop exhaust system reactors, use substitute fuels, develop cleaner power sources, use catalytic converters.

• Sources of Air pollution: Natural sources: volcanoes, seed germination. Human activities: transportation (vehicles), forest fires, agriculture, industries.

• Control of SOx (sulfur oxides) pollution: Removal of SOx gases, removal of sulphur from fuels, use of low-sulfur fuels, use of other fuel energy sources (hydroelectric or nuclear).

• Control of NOx (nitrogen oxides) pollution: Using catalytic converters, adjusting fuel combustion, introducing chemical sorbents.

• Particulate matter pollution: Includes dust, soil, smoke and liquid droplets; temperature and chemical composition are important to select proper control devices.

• Settling chambers (for particulate matter removal): Simplest device; relies on gravity; used with other, more efficient devices.

• Cyclone collectors (for particulate matter removal): Use centrifugal force to eliminate particulates

• Electrostatic precipitators (ESP): Use high voltage to charge particles to collect them

• Scrubbers: Involve entraining particulate matter into droplets of liquid

• Bag Houses Filters: Efficient for very small particles, used in filter fabrics, with cleaning methods

• Absorption (for gaseous pollutants): Used to concentrate pollutants in a liquid medium (e.g., water, caustic acid); used for recovering products/purifying gasses.

• Adsorption (for gaseous pollutants): Concentrates pollutants on a solid; materials include Bauxite, Silica gel, and molecular sieves.

• Combustion (for gaseous pollutants): Decomposes VOCs to CO2 and H2O via direct, indirect, or catalytic methods.

• Chernobyl Nuclear Disaster: April 26th, 1986 in Ukraine; major human error: reactor 4 explosion during safety test

• Pasadena TX polyethylene plant disaster: October 23, 1989: maintenance error, improper valve handling, extreme flammable gas release leading to several explosions, extensive property and business damage.

• Seveso Disaster: July 10, 1976 in Italy; chemical reactor explosion leading to the release of toxic chemicals, resulting in health issues, miscarriages, birth defects in children and extensive property damage in an approximate 18 sq km area.

• Industrial Hygiene:*

• Is concerned with the effect of all work types on health and worker ability/efficiency.

• Deals with anticipation, recognition, evaluation and control of workplace conditions that may cause injury or illness.

• Includes occupational health and safety factors leading to cancers and other health issues.

• Includes factors such as noise levels > 90 decibels, physical factors, and psychological factors at the workplace

• Occupational Diseases: Any illness associated with a particular occupation or industry, originating from biological, chemical and physical factors.

Definitions

• Safety - Freedom from unacceptable risk of harm
• Risk - Probable rate of occurrence of a hazard causing harm, and the degree of severity of harm
• Hazard - A potential source of harm.
• Harm - Physical injury or damage to health or property.
• Intended Use - Use of a product or a process in accordance with the specification and instructions provided by the supplier

Regulations/Laws

• Many Acts (e.g. Factories Act, 1948.) govern safety and environmental control in manufacturing and other operations

Additional Notes

• The provided slides likely refer to a presentation. Specific details and context of the slides may not have been fully captured in the OCR.
• Some of the technical terms and process descriptions require more detailed study/research for fully understanding the content.