Towards carbon-neutral biotechnologies for rural wastewater: A review of current treatment processes and future perspectives

With the growing awareness of carbon neutrality worldwide, the development of advanced sustainable biotechnologies for rural wastewater treatment is currently receiving extensive concern. However, characterized by its decentralized distribution and uncontrolled discharge, the treatment of rural wastewater is unavailable for an effective centralized processing through the municipal pipelines and wastewater treatment plants, which significantly increases the level of challenge for the low-carbon wastewater treatment in rural area. Without a sustainable and effective solution, the unpromising treatment process of rural wastewater inversely increases the carbon emission, economic cost and energy consumption in rural areas. This study summarized and reviewed the significance and necessity in carbon-neutral treatment of rural wastewater by investigating the advantages and flaws of currently implemented treatment processes. Some state-of-the-art bioprocesses which accord with the principle of carbon neutrality are specifically introduced due to their potential of realizing carbon neutrality in wastewater treatment. Advanced biotechnologies like anaerobic membrane bioreactor, sulfur-based autotrophic denitrification and anammox are recognized as future directions and highly recommended for the carbon-neutral treatment of rural wastewater for the removal of both organic and inorganic pollutants. This study provides new insights into the development of biotechnologies for rural wastewater treatment from the perspective of popularizing the concept of carbon neutrality in the field of wastewater treatment with energy conservation and emission reduction.