Achieving carbon neutrality by mid-21st century is of great importance to mitigate climate change. The wastewater treatment plant (WWTP) is not only a major nationwide electricity consumer but also has a significant carbon footprint. The current municipal WWTPs are still relying on the conventional activated sludge process which is energy-intensive mainly due to aeration, conflicting with the mission of carbon neutrality. Hitherto, various advanced biotechnologies have been developed and applied in practice to implement energy-saving wastewater treatment. Energy mining from wastewater by either resource recovery (e.g., biogas, alcohols, and other organics) or biowaste-to-energy conversion offer supplementary strategies to compensate the electricity consumption at WWTPs. Research and development of cutting-edge biotechnologies for energy-saving wastewater treatment is of necessity to achieve the goal of energy-positive WWTPs. How to sustain high-rate and robust biological processes for the treatment of wastewater and sludge in an energy efficient manner is the key problem that this research topic intends to address. Currently, the direct capture and redirection of carbon source from wastewater through anaerobic digestion (AD), in combination with mainstream anammox for nitrogen removal from wastewater and high-rate biogas production from sludge with AD is recognized as the most promising concept that enables energy-positive WWTPs. The worldwide implementation of this concept is still facing challenges, such as the enhancement of methane production from wastewater and/or sludge with AD under high organic loads and process stabilization and high-rate nitrogen removal with mainstream anammox. Besides, exploring emerging valuable products in addition to conventional products such as polyhydroxyalkanoates (PHA), propanediol, and glycerol from waste/wastewater deserves more efforts. The generation and re-synthesis of energetic resources and key resources to be recycled as raw materials are crucial to turn the WWTPs to energy refinery. Development and application of these biotechnologies are prerequisite towards energy positive municipal WWTPs. These technologies can also be extended to the treatment of industrial wastewaters and biowastes, which eventually contributes to the reduction of carbon footprint worldwide.This research topic intends to provide an excellent space where distinguished scientists and practitioners from all over the world will share their knowledge and experiences in approaching energy positive WWTPs. The proposed special issue publishes original research papers and review articles on all aspects of the science and technology related to wastewater treatment. Its aim is to advance and disseminate knowledge in fundamentals and applications of the biotechnologies associated with wastewater treatment, sludge treatment, and resource and energy refinery from wastewater and sludge. A broad outline of the specific themes includes: • Mainstream anammox • Carbon capture from wastewater• Anaerobic digestion• Resource recovery from sludge and wastewater: Biogas, biopolymers, and value-added products• Wastewater treatment and electricity generation with microbial fuel cells• Removal of emerging contaminants from municipal wastewater• Other novel biotechnologies relevant to wastewater treatment
Achieving carbon neutrality by mid-21st century is of great importance to mitigate climate change. The wastewater treatment plant (WWTP) is not only a major nationwide electricity consumer but also has a significant carbon footprint. The current municipal WWTPs are still relying on the conventional activated sludge process which is energy-intensive mainly due to aeration, conflicting with the mission of carbon neutrality. Hitherto, various advanced biotechnologies have been developed and applied in practice to implement energy-saving wastewater treatment. Energy mining from wastewater by either resource recovery (e.g., biogas, alcohols, and other organics) or biowaste-to-energy conversion offer supplementary strategies to compensate the electricity consumption at WWTPs. Research and development of cutting-edge biotechnologies for energy-saving wastewater treatment is of necessity to achieve the goal of energy-positive WWTPs. How to sustain high-rate and robust biological processes for the treatment of wastewater and sludge in an energy efficient manner is the key problem that this research topic intends to address. Currently, the direct capture and redirection of carbon source from wastewater through anaerobic digestion (AD), in combination with mainstream anammox for nitrogen removal from wastewater and high-rate biogas production from sludge with AD is recognized as the most promising concept that enables energy-positive WWTPs. The worldwide implementation of this concept is still facing challenges, such as the enhancement of methane production from wastewater and/or sludge with AD under high organic loads and process stabilization and high-rate nitrogen removal with mainstream anammox. Besides, exploring emerging valuable products in addition to conventional products such as polyhydroxyalkanoates (PHA), propanediol, and glycerol from waste/wastewater deserves more efforts. The generation and re-synthesis of energetic resources and key resources to be recycled as raw materials are crucial to turn the WWTPs to energy refinery. Development and application of these biotechnologies are prerequisite towards energy positive municipal WWTPs. These technologies can also be extended to the treatment of industrial wastewaters and biowastes, which eventually contributes to the reduction of carbon footprint worldwide.This research topic intends to provide an excellent space where distinguished scientists and practitioners from all over the world will share their knowledge and experiences in approaching energy positive WWTPs. The proposed special issue publishes original research papers and review articles on all aspects of the science and technology related to wastewater treatment. Its aim is to advance and disseminate knowledge in fundamentals and applications of the biotechnologies associated with wastewater treatment, sludge treatment, and resource and energy refinery from wastewater and sludge. A broad outline of the specific themes includes: • Mainstream anammox • Carbon capture from wastewater• Anaerobic digestion• Resource recovery from sludge and wastewater: Biogas, biopolymers, and value-added products• Wastewater treatment and electricity generation with microbial fuel cells• Removal of emerging contaminants from municipal wastewater• Other novel biotechnologies relevant to wastewater treatment