ASSESSMENT OF AIR QUALITY DUE TO THE EMISSIONS FROM A COAL-FIRED POWER PLANT USING A DIFFUSION MODEL

Abstract

Barapukuria Thermal Power Plant is the very first coal-based power plant in Bangladesh established in the year 2006. Currently, various coal-run electricity generating plants are in pipeline in Bangladesh. On the other hand, coal-based thermal power plants are cited to be one of the major sources of pollution affecting human health and the environment. It is therefore important to assess the impact of the emission of coal-fired power plants on ambient air quality. The objective of this study, therefore, is to simulate the dispersion and transport of pollutants emitted due to the operations of a coal-based power plant. For this study Barapukuria, Thermal Power Plant was selected. The assessment was made under two scenarios: (a) Scenario I: Plant Operating with 150 MW Capacity (3 rd unit only) and (b) Scenario II: Plant Operating with 525 MW Capacity (Maximum Capacity). A dispersion model AERMOD was used to investigate the pollutant dispersion and ground level concentration at receptor grids over a 30 x 30 km domain for a one-year period. One year (2020) meteorological data was purchased from Lakes Environmental. An extensive field study was conducted to collect ambient air quality data for validation of the model. A questionnaire survey was also conducted among the people living in the vicinity of the power plant to assess the impact on human health. Simulation results showed that the radius of impact of the emissions is approximately 5 km. The concentration of emissions at receptors located in the southwestern direction was found to be higher as the winds carried the pollutant clouds in their direction. The predicted peak concentrations of SO2 in the area are 18.62 μg/m3, 3.19 μg/m3, and 0.82 μg/m3 for 1- hr, 24-hr, and annual averaging periods respectively. Similarly, the predicted maximum concentrations of NOx in that area are found to be 33.56 μg/m3, 5.75 μg/m3, and 1.48 μg/m3 for 1-hr, 24-hr, and annual averaging periods respectively. The peak concentrations of CO ii are 9.32 μg/m3, 1.59 μg/m3, and 0.41 μg/m3 for 1-hr, 24-hr, and annual averaging periods respectively. The predicted resultant concentration of NOx exceeds WHO guideline values whereas SO2 and CO concentrations comply with Bangladesh air quality standards and WHO guideline values. The predicted peak concentration of pollutants (SO2, NOx, and CO) over the modeled area increases about five times from scenario I (only the 3rd unit, operating with 150 MW capacity) to Scenario II (all units operating with 525 MW capacity). Assessment of seasonal and diurnal variation of pollutants showed that change in pollutant behavior is largely dictated by meteorological parameters. Over a particular day, the peak concentration of pollutants is typically reached in the morning to noon. The dispersion model results were compared with the air quality data measured at the same location to validate the model. The performance evaluation, with the aid of statistical measures, revealed that the models’ performance was acceptable. From the model output results, the field measured ambient air quality data, and the questionnaire survey it can be concluded that the maximum emissions of air pollutants (SO2, NOx, CO) due to the power plant operation is not harmful to the health of the people living in the vicinity of the plant.