Stack emissions from desalination plants: a parametric sensitivity analysis for exposure assessment

The desalination market has been continuously growing to augment conventional water resources in arid and semi-arid regions that are experiencing population growth, improvements in life-style, increased economic activity and increased contamination of existing water supplies. The introduction of desalination plants is inevitably associated with several potential environmental impacts including potential air pollution. The present study focuses on qualifying air emissions resulting from desalination plants and their potential impacts using a case study approach for an existing combined power generation and water distillation plant. The Industrial Source Complex (ISC) air dispersion model was adopted to assess sulfur dioxide concentrations at sensitive receptors under worst case meteorological conditions and full load operation for both plants. A parametric sensitivity analysis showed that receptors are exposed to concentrations exceeding international standards under most scenarios necessitating mitigation measures which were defined.

Potential impacts on air quality constitute a serious environmental concern associated with the introduction of a desalination plant into an area and must be considered during the site, technology and fuel type selection process at the design phase. In this study, air dispersion simulations were conducted to assess the impact of SO2 stack emissions from a typical combined desalination–power plant on ambient air quality in the Arabian Gulf. Simulation results revealed that at several instances both near and far field receptors are prone to be exposed to concentrations exceeding health standards. A parametric sensitivity analysis indicated that stable to neutral atmospheric conditions with low wind speeds and mixing heights were responsible for worst case exposure levels. Both fuel-targeted measures (low sulfur content fuel oil or natural gas) and end of pipe control equipment (flue gas desulphurization units or scrubbers) can eliminate or reduce the exposure levels to below health standards, whereby the use of low sulfur HFO will decrease SO2 emissions by 72%, while shifting to natural gas or installing scrubbers will almost eliminate sulfur dioxide emissions.