The anaerobic digestion process produces methane while stabilizing sludge. As of 2020, 62 anaerobic digesters in public wastewater treatment plants are operational in Korea. Many researchers have studied to improve digester performance. Thermal hydrolysis technology is one of the pre-treatment methods for treating sludge. Reduced retention time and enhanced biogas production are the main advantages of sludge disintegration at relatively high temperatures and pressures. But nutrients like nitrogen and phosphorus are released from the pre-treated sludge. Phosphorus is a non-renewable resource that is essential to food production. Wastewater receives 20% of the total phosphate discharge, while 90% of the influent phosphorus load is in sludge. For efficient phosphorus recovery, it is essential to comprehend the phosphorus release characteristics during wastewater treatment, including anaerobic digestion. Biological or chemical processes can achieve phosphorus removal to comply with the effluent discharge limits regulations. The three primary sources of phosphorus in sludge are aluminum-bound phosphorus (Al-P), polyphosphate in phosphorus-accumulating organisms (PAOs), and iron-bound phosphorus (Fe-P). Anaerobic digestion is the typical method for recovering carbon and phosphorus. However, previous research has demonstrated that most phosphorus in anaerobic digestion occurs as a solid phase coupled with heavy metals. Therefore, the poor mass transfer rate results in a slow phosphorus release. Due to the recent growth in interest and significance of phosphorus recovery, many researchers have studied to improve the quantity of phosphorus released into the liquid phase through chelation addition, process operation optimization, and disintegration using sludge pre-treatment. The study aims to investigate characteristics of the phosphorus release associated with the thermal hydrolysis breakdown of sludge and propose a method for recovering phosphorus in a wastewater treatment plant. When solubilizing sludge using thermal hydrolysis pre-treatment, organic phosphates, inorganic phosphates, and polyphosphates are converted into ortho-phosphate. Therefore, applying thermal hydrolysis, anaerobic digestion, and phosphorus recovery processes (struvite formation or microbial electrolysis cells) can recover carbon and phosphorus.

ABSTRACT
1. 서 론
2. 하수슬러지 가용화 기술
3. 하수슬러지의 혐기성 조건에서의 인방출 기작
4. 하수슬러지의 혐기성 인 방출 효율 증진
5. 하수슬러지의 탄소 및 인 회수 방안
6. 결론 및 제언
감사의 글
References

• 이채영(수원대학교 건설환경공학과) | Chaeyoung Lee (Civil and Environmental Engineering, The University of Suwon)
• 한선기(한국방송통신대학교 보건환경학과) | Sun-Kee Han (Department of Environmental Health, Korea National Open University) Corresponding author