2012년부터 강화된 총인의 농도를 준수하기 위해서는 응집에 의한 물리화학적 처리가 필수적인 후단공정이 되었으며, 현재 국내 하수처리시설 중 약 60%의 처리시설에서 총인처리시설이 설치되었다. 하지만 총인처리시설 운전에 따른 응집제 사용량이 증가하게 되었고, 이에 따라 약품 비용 및 슬러지 처리비 증가 등의 운영비가 상승하였다. 특히 분리막 공법(MBR)의 경우 막 투과수의 응집액 부족으로 인한 응집효율 저하 및 응집제의 과다 주입으로 인한 처리수질 악화 등의 문제가 발생하는 경우도 있다. 본 연구에서는 MBR 공법내에서 별도의 총인처리시설 필요 없이 생물학적 인제거를 극대화 하는 동시에 응집제 사용량을 최소화하면서 처리수의 인농도를 0.2 mg/L 이하로 유지할 수 있는 방안을 도출하고자 하였다.

A membrane bioreactor by sequentially alternating the inflow and by applying a two-stage coagulation control based on pre-coagulation was evaluated in terms of phosphorus removal efficiency and cost-savings. The MBR consisted of two identical alternative reaction tanks, followed by aerobic, anoxic and membrane tanks, where the wastewater and the internal return sludge alternatively flowed into each alternative reaction tank at every 2 hours. In the batch-operated alternative reaction tank, the initial concentration of nitrate rapidly decreased from 2.3 to 0.4 mg/L for only 20 minutes after stopping the inflow, followed by substantial release of phosphorus up to 4 mg/L under anaerobic condition. Jar test showed that the minimum alum doses to reduce the initial PO4-P below 0.2 mg/L were 2 and 9 mol-Al/mol-P in the wastewater and the activated sludge from the membrane tank, respectively. It implies that a pre-coagulation in influent is more cost-efficient for phosphorus removal than the coagulation in the bioreactor. On the result of NUR test, there were little difference in terms of denitrification rate and contents of readily biodegradable COD between raw wastewater and pre-coagulated wastewater. When adding alum into the aerobic tank, alum doses above 26 mg/L as Al2O3 caused inhibitory effects on ammonia oxidation. Using the two-stage coagulation control based on pre-coagulation, the P concentration in the MBR effluent was kept below 0.2 mg/L with the alum of 2.7 mg/L as Al2O3, which was much lower than 5.1∼7.4 mg/L as Al2O3 required for typical wastewater treatment plants. During the long-term operation of MBR, there was no change of the TMP increase rate before and after alum addition.

Capacitive deionization(CDI) has many advantages over other desalination technologies due to its low energy consumption, less environmental pollution and relative low fouling potential. The objectives of this study are evaluate the performance of CDI which can be used for dissolved salts removal from sewage. To identify ion selectivity of nitrate and phosphate in multi-ionic solutions and adsorption/desorption performance related to applied potential, a series of laboratory scale experiments were conducted using a CDI unit cell with activated carbon electrodes. The CDI process was able to achieve more than 75 % TDS and NO3-, NH4+ removals, while phosphate removal was 60.8 % and is inversely related in initial TDS and H3- concentration. In continuous operation, increasing the inner cell pressure and reduction of TDS removal ability were investigated which are caused by inorganic scaling and biofouling. However a relative mild cleaning solution(5 % of citric acid for calcium scaling and 500 mg/L of NaOCl for organic fouling) restored the electrochemical adsorption capacity of the CDI unit to its initial level.

본 연구는 자연수중의 미생물을 식종원으로 하는 TOC-HANDAI법과 OECD 생분해법을 활용하여 자연수 환경내에서 환경호르몬물질인 비스페놀 A와 노닐페놀의 생분해성을 비교평가하였다. TOC-HANDAI법에 의한 BPA분해는 73-78% 이었고 OECD법은 이보다 다소 높은 77-81%를 나타내었다. 두 방법을 통한 BPA의 분해양상은 대체로 2단계를 거쳐 진행되었다. 즉 초기 1주일 이내에는 분해반응속도(k1)가 0.24-0.34day-1