Nitrogen removal of thermal hydrolysis-anaerobic digestion liquid: A review

Thermal hydrolysis (TH) pretreatment, as an anaerobic digestion (AD) pretreatment, has not only been verified in the laboratory but also frequently employed in actual engineering. However, the properties of anaerobic digestion liquid (ADL), such as high organic matter concentration, high ammonia nitrogen (NH4+-N) concen-tration, and low carbon-nitrogen ratio (C/N), have posed some difficulties in the follow-up treatment. To address the above issues, the autotrophic nitrogen removal (ANR) process is developed to treat ADL. Due to the NH4+-N, organic materials, toxic and harmful substances in the ADL that might directly impact the activity of functional bacteria, the ADL should be treated before being fed into the ANR process. This paper provided a focused review of the thermal hydrolysis-anaerobic digestion process (TH-ADP) mechanism and the ANR mechanism, summa-rized the existing difficulties in the treatment of thermal hydrolysis-anaerobic digestion liquid (TH-ADL), assessed the research status thoroughly, and offered the potential solutions to the problems.

Automated summary

Thermal hydrolysis (TH) pretreatment, used in anaerobic digestion (AD), has been proven effective in the laboratory and utilized in engineering. However, the properties of AD liquid (ADL), such as high organic matter and ammonia nitrogen concentration, present challenges in subsequent treatment. To overcome this, the autotrophic nitrogen removal (ANR) process is developed. This paper reviews the TH-ADP and ANR mechanisms, addresses difficulties in treating TH-ADL, evaluates current research status, and proposes potential solutions.