Problem/Challenge:

The proposed development of a Regional General Waste Landfill in the City of Tshwane raised concerns about potential negative impacts on ambient air quality. These concerns stem from emissions expected during landfill operations, including dust, hazardous air pollutants (HAPs), and odorous gases such as hydrogen sulphide, ammonia, and various volatile organic compounds. The surrounding area includes sensitive receptors like residential communities, schools, and clinics, increasing the need for a detailed air quality impact evaluation.

Solution/Approach Taken:

To address these concerns, an Air Quality Impact Assessment (AQIA) was undertaken. This included:

• Baseline assessment of meteorological data and ambient air quality.
• Identification of sensitive receptors and existing local emission sources.
• Development of an emissions inventory covering landfill gas, flare emissions, odours, and dust sources.
• Dispersion modelling using AERMOD to predict the concentration of pollutants under worst-case operational scenarios.
• Comparison of predicted values with national ambient air quality standards, dust control regulations, and international guidelines for pollutants lacking South African standards.

Modelling results indicated that, while most emissions would comply with applicable standards, exceedances of certain pollutants (such as dimethyl sulphide, ammonia, hydrogen sulphide, and trichloroethylene) were predicted near the landfill boundary and in some nearby areas. Odour impacts were also likely within a few kilometres of the site, especially downwind.

Mitigation measures were recommended, including dust suppression, odour control, use of enclosed facilities for waste processing, waste sorting to reduce organic content, and a landfill gas capture and flaring system. A leachate management system was also included in the design by the landfill developers to limit hydrogen sulphide emissions.

Role of Rayten Engineering:

Rayten Engineering Solutions acted as the air quality specialist for the project. Their responsibilities included:

• Conducting a comprehensive site and baseline assessment.
• Identifying pollutants of concern and their potential health and odour impacts.
• Compiling detailed emissions inventories for various sources.
• Executing dispersion modelling simulations using regulatory-compliant tools.
• Evaluating compliance with national and international standards.
• Proposing targeted mitigation and monitoring strategies to manage emissions and odour impacts effectively.

Through their technical expertise and modelling analysis, Rayten Engineering provided the necessary scientific basis to inform licensing decisions and ensure the proposed landfill’s compliance with environmental and public health standards.