Hydrogen Sulphide and Odour Emissions Control in Wastewater Treatment Plants (WWTPs) by an Integrated Sustainable Biotechnological System

Wastewater treatment plants (WWTPs) play a crucial role in the water cycle. These facilities ensure the balance of the ecosystem and avoid significant negative effects on the environment and human health. However, they also exert negative pressures. Among these, odours and odorous compound emissions, principally hydrogen sulphide (H2S), require more attention. Prolonged exposure to odour emissions produces negative effects on exposed populations, such as nausea, headaches, and other related respiratory problems. The perception of odours is also considered a sign of a polluted environment and therefore the first cause of complaints. In this context, there is a need to characterize and control odour emissions. Currently, among the odour treatment processes, biological ones show the greatest potential for future development, as they are cheaper and more sustainable for the environment. However, decomposition by microorganisms with oxidative properties produces carbon dioxide, which is one of the main greenhouse gases and contributes to global warming. The research presents and discusses the application and validation of an advanced sustainable biological-based system aimed at treating odours and avoiding the release of GHG into the ambient air, thus ensuring clean air and mitigating climate change according to the Sustainable Development Goals (SDGs) of the Agenda 2030. In-depth and extensive experimental activities are carried out and reported to validate the proposed system, consisting of an integration of a Moving Bed Biofilm Reactor (MBBR) and an algal Photobioreactor (aPBR). System performance has been evaluated under different operating conditions, with reference to H2S removal efficiencies and CO2 abatement rates and subsequent conversion to usable biomass. The analyses also included the determination of the concentration of odours according to EN 13725:2022. The results obtained confirm the efficiency of the proposed system in reducing odours and biofixation of CO2, promoting a novel advanced and environmentally friendly solution in odour treatment.