Air quality modeling

Air quality modelling can be defined as a tool for developing and evaluating air quality policy by utilizing mathematical theory to understand or predict how contaminants behave in the atmosphere. The preparation of air quality modelling involves a site selection for monitoring or choosing the existent meteorological data base. The importance of this modelling is it allows better understanding on air pollutants relative concentration that is used in achieving cost-effective pollution control measures. The modelling can be use in reducing harmful air pollutants by:

  • Estimating relationship between sources of contaminants and how they influence ambient air quality
  • Identifying source contributions that cause air quality problems
  • Assisting in designing effective strategies for air pollution control measures

Stack Emission Sampling

Stacks were used as a method of pollution control where these days they are the final component of most highly complex air pollution control or ventilation systems. Stacks emission sampling is a method of evaluating the characteristics of air pollutants emitted into the atmosphere from a given source within an allocated time. (e.g. industrial waste gas stream emission). Air pollutants emission can be in several form such as solid, liquid, inorganic gas or organic gas. Stacks emission sampling is performed in order to:

  • Determine effectiveness of control equipment
  • Determine specific source contribution to the receptor environment
  • Provide data for dispersion modelling
  • Provide data for process efficiency

Local Exhaust Ventilation (LEV) Test

A simple definition of ventilation is “the control of the environment with airflow” whereby the system is designed for commercial, residential or industrial applications. Generally, it is used to control airborne hazards by exhausting or supplying air to remove air pollutants at their source or dilute them to a safe level. Industrial ventilation can be defined as the mechanical systems to control contaminant levels in the workplace that brings in ‘fresh’ outdoor air and removes the ‘contaminated’ indoor air. In industrial premises, the two common types of mechanical ventilation are dilution ventilation and local exhaust ventilation. Dilution ventilation (also known as general industrial ventilation) operates by controlling hazardous atmosphere or decreasing air pollutants concentration through diluting the atmosphere to a safe level using either exhausting or supplying air to the general area.

For local exhaust ventilation (LEV), the system attempts to enclose any material, equipment or process as much as possible and to withdraw contaminated air in order to assure that the air movement direction at all openings is always into the enclosure. The LEV system controls air contaminants by trapping them at or near the source, in contrast to dilution ventilation which lets the contaminant spread throughout the workplace. The concept of LEV is installing exhaust system at or near the source of pollutants which is more efficient at removing pollutants. When it is properly designed, the pollutants are removed before they get into the general work environment or worker’s breathing zone. Commonly, most LEV systems consist of a combination of hoods, duct components, air cleaning device(s), a fan and a stack. The system must be properly designed, balanced and commissioned to ensure proper performance and achieve economic efficiency.

LEV equipment installation must be complied to the Regulation 18 of Occupational Safety and Health (Use and Standards of Exposure of Chemicals Hazardous to Health) Regulations 2000 (USECHH, 2000) (pdf 3) which stated that:

  • Without prejudice to the requirement of sub regulation 17 (1), any local exhaust ventilation equipment installed shall be –
    • Designed according to an approved standard by a registered professional engineer and constructed according to the design specifications; and
    • Tested by a registered professional engineer after construction and installation to demonstrate that the equipment meets the design specifications.

Wastewater Sampling

Wastewater sampling provides information regarding the status or quality of the wastewater whether it is complying with the standard requirement before discharging them to water bodies or re-using them. Wastewater quality refers to the chemical, physical and biological parameters of water with respects to its suitability or a particular purpose. The parameters include Biochemical Oxygen Demand (BOD), Suspended solids (SS), Chemical Oxygen Demand (COD), Total Nitrogen (TN), Ammoniacal Nitrogen (NH3 – N), Total Phosphorus (TP) and Oil and Grease (O&G). Information received from wastewater sampling determines whether the wastewater requires further treatment or suitable to be released to water bodies or recycled. The parameter limits of effluent is categorized in Standard A and B, following the Environmental Quality (Sewage and Industrial Effluents) Regulations 2009 (pdf 4).

Eco Environmental Engineering is currently offering services involving air quality modelling, stack sampling, LEV testing and wastewater sampling covering all states in Malaysia.




References

Air Quality Modeling, Stack Emission Sampling, Wastewater Sampling

Local Exhaust Ventilation (LEV) Test