A Review of NH3 and H2S Biofiltration for Odour Control: Mechanisms, Media, Microbial Communities, and Performance Optimization

Air pollution caused by the release of odorous gases such as ammonia (NH3), hydrogen sulphide (H2S) and volatile organic compounds (VOCs) has become a serious environmental concern in our society. These emissions not only disrupt operations in wastewater and other waste processing facilities, but also pose a significant health risk to the nearby communities. Conventional odour control techniques, although effective, are constrained by high operational costs and generation of secondary pollutants including NO2, CO and other greenhouse gases. Biofiltration has emerged as a sustainable alternative, offering lower energy consumption, improve cost-effectiveness and operational simplicity. However, the long-term performance and stability of the biofilters are influenced by factors such as seasonal temperature fluctuations, acidification, and biomass accumulation. These challenges can be mitigated through selection of appropriate packing media and microbial community. In this context, the present literature review focuses on how the media properties such as moisture retention capacity, buffering capacity, sorption potential, and acid tolerance affect the performance of nitrifying and sulphur-oxidizing bacteria. In addition, the challenges of pH incompatibility in single medium for simultaneous NH3 and H2S biofiltration is also addressed in this review. The review highlights media-specific benefits, noting that inorganic media are more resistance to acidification, and favour sulphur oxidation, whereas organic media provide buffering capacity and nutrient availability, supporting the nitrification process. The review also compares different reactor configurations for biofilter, considering the removal efficiency, performance under fluctuating loads, and long-term stability.