The efficiencies of Gang-Byeon sewage treatment facilities, which are based on GPS-X modelling, were analysed and used to design recycle water treatment processes. The effluent of an aeration tank contained total kjeldahl nitrogen (TKN) of 1.8 mg/L with both C-1 and C-2 conditions, confirming that most ammonia nitrogen (NH3 +-N) was converted to nitrate nitrogen (NO3 --N). The concentrations of NH3 +-N and NO3 --N were found to be 222.5 and 227.2 mg/L, respectively, with C-1 conditions and 212.2 and 80.4 mg/L with C-2 conditions. Although C-2 conditions with higher organic matter yielded a slightly higher nitrogen removal efficiency, sufficient denitrification was not observed to meet the discharge standards. For the total nitrogen (T-N) removal efficiency, the final effluent concentrations of T-N were 293.8 mg/L with biochemical oxygen demand (BOD) of 2,500 mg/L, being about 1.5 times lower than that (445.3 mg/L) with BOD of 2,000 mg/L. Therefore, an external carbon source to increase the C/N ratio was required to get sufficient denitrification. During the winter period with temperature less than 10 , the denitrification efficiency was dropped rapidly even with a high TKN concentration (1,500 mg/L). This indicates that unit reactors (anoxic/aerobic tanks) for winter need to be installed to increase the hydraulic retention time. Thus, to enhance nitrification and denitrification efficiencies, flexible operations with seasons are recommended for nitrification/anoxic/denitrification tanks.

Abstract
 1. 서 론
 2. 연구방법
  2.1. 강변하수처리장의 공정 분석
  2.2. 반류수 처리시설 용량 추정
 3. 결과 및 고찰
  3.1. BOD 부하에 따른 유출수 농도 변화
  3.2. 동절기 질산화율 모델링 결과
 4. 결 론
 감사의 글
 REFERENCES

• 신춘환(동서대학교 에너지환경공학과, Department of Energy & Environmental Engineering, Dongseo University) | Choon Hwan Shin Corresponding author