With rapid economic growth, increasing emission of wastewater tends to aggravate environmental pollution. This has become a serious issue haunting social and economic development worldwide. Therefore, wastewater treatment is quite imperative for sustainable development and is critical for ecosystem and human health. Typically, wastewater is purified through microbial biotechnology, where carbon, nitrogen, and phosphorus are removed. Archaea are important in wastewater treatment and they are responsible for methane production, carbon mineralization, nitrification, and denitrification. Besides, newly discovered denitrifying anaerobic methane oxidation (DAMO) process, through which methane is oxidized anaerobically, also requires archaea involvement. Still, haloarchaea are adapted to saline environment and can treat saline wastewater efficiently. To date, many archaea in wastewater treatment are identified and characterized, and steady state is achieved in archaea-based wastewater treatment process. This benefits pollutant removal with good potential for decreasing chemical and energy use. Like other microbial technologies, archaea-based process is developing quickly with exciting breakthrough in both theory improvement and technology innovation in wastewater treatment.

Archaea-based technology is essential for wastewater treatment by integrating energy production and resource recovery into producing clean water. Archaea play quite important role in converting or removing carbon, nitrogen, phosphorus, and other pollutants. However, compared with bacteria in wastewater treatment, many issues on archaea such as community structure, metabolism mechanism, and the like are still not well known. A comprehensive understanding about identity, physiology, ecology, and population dynamics of archaea will improve wastewater treatment efficiency and process stability. It will be possible to find selective principles for regulating certain population and managing microbial community. It is quite necessary to further study archaea in wastewater treatment. Such investigations can not only optimize current wastewater treatment process but also innovate emerging technology.

This special issue focuses on archaea in wastewater treatment. We invite scholars specialized in microbiology or environmental engineering to submit high-quality original research articles as well as reviews exploring any aspect of archaea in wastewater treatment.

Potential topics include but are not limited to the following:

• Identity, physiology, ecology, and population dynamics of ammonia-oxidizing archaea in wastewater treatment
• Relationships between ammonia-oxidizing archaea and bacteria and their abundance and distribution in wastewater treatment
• Characteristics, activity, and diversity of archaea in denitrifying anaerobic methane oxidation
• Nitrogen removal performance and mechanism through synergy between archaea and bacteria in denitrifying anaerobic methane oxidation
• Simultaneous pollutant removal and methane production in anaerobic digestion
• Competition between methane-producing archaea and sulfate-reducing bacteria in anaerobic digestion
• Haloarchaea in saline wastewater treatment
• Archaea in industrial wastewater treatment
• Molecular method studying archaea-based microbial ecology in wastewater treatment
• Reactor performance and regulation strategy of archaea-based wastewater treatment process
• Emerging archaea-based technology in wastewater treatment