Abstract
Hydrogen sulphide (H2S) is a well-known environmental pollutant from the industrial sector due to its unpleasant odour and high toxicity. It can post health threat at a low threshold exposure limit, with concentration as low as 0.01-1.5 ppm. In the pulp and paper mills, a significant amount of total reduced sulphur (TRS) is generated during the pulping and bleaching process. The TRS contains various pollutants such hydrogen sulphide (H2S), methyl mercaptan and dimethyl. For recycled paper mills, since the collected papers did not undergo the pulping and bleaching processes, the pollutant produced is mainly H2S. Due to its high toxicity and low threshold limit, early H2S detection and understanding its air dispersion pattern are important to reduce the potential health risk imposed by H2S to the local workers and residence of the surrounding areas. However, the commonly used odour unit might not be sufficient to represent the specific concentration of H2S. There has also been limited studies on the H2S dispersion modelling in Malaysia. Thus, in this study, a H2S dispersion modelling was performed at a recycled paper mill in Malaysia, with H2S concentration (µg/m3) as the odour indicator, to understand the changes in H2S concentration at different distances from source and identify potential health risk. Firstly, air samples were collected and analysed to identify the emission hotspots. The American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) was then used to determine the dispersion pattern of H2S and its concentration across the surrounding air. Wind data for 2 y was recorded and input for the modelling. Both the gas sampling study and dispersion modelling showed that the concentration of H2S was below the threshold limit at a distance of 50 m from the emission source, which was the effluent sludge holding tank. It is unlikely that the H2S emission from the recycled paper mill would lead to odour or health complaints to the surroundings.
