하수처리장 에너지 자립화를 위한 하수 에너지 잠재력 회수 기술

Abstract

Domestic sewage treatment plants (STPs) consume about 0.5 % of total electric energy produced annually, which is equivalentto 207.7 billion Korean won per year. To minimize the energy consumption and as a way of mitigating the depletion of energysources, the sewage treatment strategy should be improved to the level of “energy positive”. The core processes for the energypositive sewage treatment include A-stage for energy recovery and B-stage for energy-efficient nitrogen removal. Theintegrated process is known as the A/B-process. In A-stage, chemically enhanced primary treatment (CEPT) or high rateactivated sludge (HRAS) processes can be utilized by modifying the primary settling in the first stage of sewage treatment. CEPT utilizes chemical coagulation and flocculation, while HRAS applies returned activated sludge for the efficient recoveryof organic contents. The two processes showed organic recovery efficiencies ranging from 60 to 70 %. At a given recoveryefficiency of 80 %, 17.3 % of energy potential (1,398 kJ/m3) is recovered through the anaerobic digestion and combustion ofmethane. Besides, anaerobic membrane bioreactor (AnMBR) can recover 85% of organic contents and generate 1,580 kJ/m3from the sewage. The recovered energy is equal to the amount of energy consumption by sewage treatment equipped withanaerobic ammonium oxidation (ANAMMOX)-based B-stage, 810 ~ 1,620 kJ/m3. Therefore, it is possible to upgrade STPs asefficient as energy neutral. However, additional novel technologies, such as, fuel cell and co-digestion, should be applied toachieve “energy positive” sewage treatment.