A system engineering perspective for net zero carbon emission in wastewater and sludge treatment industry: A review

This study systematically reviews greenhouse gas (GHG) emissions reduction strategies in wastewater treatment industry from a system engineering perspective. It highlights the lack of comprehensive assessments across the wastewater treatment industry, incorporating both wastewater treatment plants (WWTPs) and sludge management, to understand the full GHG emissions landscape. Suitable processes and technologies for GHG control have been identified, which emphasizes the importance of on-site N2O emission control, operational efficiency, energy source shifts, and increased sludge incineration. Through life cycle assessment (LCA) evaluation, plant-wide models exhibited the best performance of GHG emission control from operational stages, while technologies recovering energy from both wastewater and sludge can greatly mitigate 25–100 % GHG emissions. The paper also suggests hydrothermal processes, especially wet oxidation as preferable to avoid GHG emissions from sludge management, urging future research toward multi-technology integration and collaborative management strategies for effective GHG mitigation.