Engineering of Air pollution

Engineering of Air Pollution, Its Control and Monitoring

Definition of Air Pollution

  • Air pollution is the presence of solid, liquid, or gaseous substances in the atmosphere.

  • It becomes harmful when pollutant concentrations exceed the self-cleansing capacity of ambient air.

  • Air pollution can injure human beings, living creatures, plants, and property.

Sources and Classification of Air Pollution

Natural Sources

  • Dust, pollen, fungal spores, and smoke from fires/volcanic eruptions.

Anthropogenic Sources

  • Emissions from combustion and heating processes in industries.

  • Manufacturing of chemicals, petroleum products, food processing, and agriculture.

Types of Contaminants

  1. Aerosols (Particulates)

    • Particles larger than a molecule that can remain suspended in air, such as dust, smoke, mist, and fog.

  2. Gases and Vapors

    • Various gaseous pollutants dispersed in the atmosphere.

Classification of Air Pollutants

Based on Formation

  1. Primary Air Pollutants

    • Directly emitted from identifiable sources, e.g., particulate matter, sulphur compounds, nitrogen compounds, carbon monoxide, carbon dioxide, lead, hydrocarbons, radioactive materials, halogen compounds.

  2. Secondary Air Pollutants

    • Formed through the interaction of primary pollutants or reactions with atmospheric constituents (with/without photo activation).

    • More harmful examples: sulphuric acid, ozone, formaldehyde, PAN, photochemical smog.

Total Suspended Particulate Matter (TSPM) and RSPM

RSPM (Respiratory Suspended Particulate Matter)

  • Smaller particles (up to 10 microns) that can penetrate lung tissues causing health issues such as asthma, bronchitis, and lung cancer.

  • Monitoring of smaller particles (up to 2.5 microns, PM 2.5) is crucial due to their greater harmful effects.

Methods of Controlling Air Pollution

  1. Zoning

    • City planning to ensure residential areas are not situated near heavy industries.

  2. Dilution

    • Use of tall stacks (chimneys) to disperse pollutants.

  3. Source Correction

    • Changing raw materials, process methods, or equipment to reduce emissions at the source.

  4. Pollutant Discharge Reduction

    • Implementation of controlling equipment at the source to minimize discharges.

Equipment for Control of Particulate Pollutants

  1. Gravity settling chambers

  2. Cyclonic separators (cyclones)

  3. Fabric filters

  4. Electrostatic precipitators

  5. Scrubbers or wet collectors