Hydrogen sulphide is a toxic gas, it can cause a range of physiological responses from simple annoyance to permanent injury and death. There are a number of approaches to deal with the impacts of toxic gases. This study focused on minimizing the hazard exposure for hydrogen sulfide in the different operational zones for activated sludge process in sewage waterplant. Research tools/ approaches conducted were interviews, toxic gas testers, analysis report interpretation & quantitative risk assessment method. The study was conducted on Arabian Peninsula during the period (September 2019- September 2021). The (13) operational locations tested for toxic gas concentrations were inlet chamber, outlet channel, coarse /fine screens, primary sedimentation tank, activated sludge tanks, secondary sedimentation tanks, gas desulfurization unit, disc filters, chlorine dosing unit, sludge dewatering, sludge silos and digester tanks. The study found that the highest concentration for H<sub>2</sub>S in the inlet chamber/ outlet channel. The severity hazards in the sewage treatment plant using activated sludge process are the asphyxiation by H<sub>2</sub>S was extremely high can cause harm to public health, followed by the radiation hazard followed by electrical hazard, then (working at height, mechanical, traffic, health, chemical, physical, ergonomic, environmental, microbial and natural). The frequency of hazards occurrence is asphyxiation by H<sub>2</sub>S was extremely high followed by the radiation hazard and health hazard including the infection with Covid 19 virus followed by mechanical hazard then (electrical, traffic, ergonomic, natural, chemical, physical and natural). Control measures were recommended to minimize the risk of asphyxiation by H<sub>2</sub>S in the working environment at the STP.
Tolerable Risk for Hydrogen Sulfide in Sewage Treatment Plant- STP