High-pressure membrane system like nanofiltration(NF) and reverse osmosis(RO) was investigated as a part of water treatment processes to produce high quality potable water with low organic matter concentration through membrane module tests and design simulation. River water and sand filtration permeate in Busan D water treatment plant were selected as feed water, and NE4040-90 and RE4040-Fen(Toray Chemical Korea) were used as NF and RO membranes, respectively. Total organic carbon(TOC) concentrations of NF and RO permeates were mostly below 0.5 mg/l and the average TOC removal rates of NF and RO membranes were 93.99% and 94.28%, respectively, which means NF used in this study is competitive with RO in terms of organic matter removal ability. Different from ions rejection tendency, the TOC removal rate increases at higher recovery rates, which is because the portion of higher molecular weight materials in the concentrated raw water with increasing recovery rate increases. Discharge of NF/RO concentrates to rivers may not be acceptable because the increased TDS concentration of the concentrates can harm the river eco-system. Thus, the idea of using NF/RO concentrate as the raw water for industrial water production was introduced. The design simulation results with feed water and membranes used in this work reveal that the raw water guideline can be satisfied if the recovery rate of NF/RO system is designed below 80%.

In the membrane process, it is important to improve water treatment efficiency to ensure water quality and minimize membrane fouling. In this study, a pilot study of membrane process using reservoir water was conducted for a long time to secure high flux operation technology capable of responding to influent turbidity changes. The raw water and DAF(Dissolved Air Flotation) treated water were used for influent water of membrane to analyze the effect of water quality on the TMP (Trans Membrane Pressure) and to optimize the membrane operation. When the membrane flux were operated at 70 LMH and 80 LMH under stable water quality conditions with an inlet turbidity of 10 NTU or less, the TMP increase rates were 0.28 and 0.24 kPa/d, respectively, with minor difference. When the membrane with high flux of 80 LMH was operated for a long time under inlet turbidity of 10 NTU or more, the TMP increase rate showed the maximum of 43.5 kPa/d. However, when the CEB(Chemically Enhanced Backwash) cycle was changed from 7 to 1 day, it was confirmed that the TMP increase rate was stable to 0.23 kPa/d. As a result of applying pre-treatment process(DAF) on unstability water quality conditions, it was confirmed that the TMP rise rates differed by 0.17 and 0.64 kPa/d according to the optimization of the coagulant injection. When combined with coagulation pretreatment, it was thought that the balance with the membrane process was more important than the emphasis on efficiency of the pretreatment process. It was considered that stable TMP can be maintained by optimizing the cleaning conditions when the stable or unstable water quality even in the high flux operation on membrane process.

Membrane filtration has been considered as an promising harvesting technology in the fields of microalgal biorefinery to produce biofuels and valuable chemicals from microalgal biomass. For developing the effective membrane-based harvesting process to produce highly concentrated biomass, membrane fouling should be controlled because it leads to not only reduced filtration rate but also insufficient reachable concentration of harvested biomass for downstream process. For that, a dynamic filtration using a rotating disk was evaluated in this study, efficiently generating high shear flow near the membrane surface by an independently moving part. It was demonstrated to achieve feasible filtration performance even under high biomass concentration with complete biomass recovery and moderate energy consumption observed.

In this study, the effects of operating conditions on the formation of reversible and irreversible fouling were investigated in the filtration using ceramic membrane for water treatment process. The effect of coagulation pretreatment on fouling formation was also evaluated by comparing the performance of membrane filtration both with and without addition of coagulant. A resistance-in-series-model was applied for the analysis of membrane fouling. Total resistance (RT) and internal fouling resistance (Rf) increased in the membrane filtration process without coagulation as membrane flux and feed water concentrations increased. Internal fouling resistance, which was not recovered by physical cleaning, was more than 70% of the total resistance at the range of the membrane flux more than 5 m3/m2･day. In the combined process with coagulation, the cake layer resistance (Rc) increased to about 30-80% of total resistance. As the cake layer formed by coagulation floc was easily removed by physical cleaning, the recovery rate by physical cleaning was 54~90%. It was confirmed from the results that the combined process was more efficient to recover the filtration performance by physical cleaning due to higher formation ratio of reversible fouling, resulted in the mitigation of the frequency of chemical cleaning.

In water treatment process using microfiltration membranes, manganese is a substance that causes inorganic membrane fouling. As a result of analysis on the operation data taken from I WTP(Water Treatment Plant), it was confirmed that the increase of TMP was very severe during the period of manganese inflow. The membrane fouling fastened the increase of TMP and shortened the service time of filtration or the cleaning cycle. The TMP of the membrane increased to the maximum of 2.13 kgf/cm2, but it was recovered to the initial level (0.17 kgf/cm2) by the 1st acid cleaning step. It was obvious that the main membrane fouling contaminants are due to inorganic substances. As a result of the analysis on the chemical waste, the concentrations of aluminum(146-164 mg/L) and manganese(110-126 mg/L) were very high. It is considered that aluminum was due to the residual unreacted during coagulation step as a pretreatment process. And manganese is thought to be due to the adsorption on the membrane surface as an adsorbate in feed water component during filtration step. For the efficient maintenance of the membrane filtration facilities, optimization of chemical concentration and CIP conditions is very important when finding the abnormal level of influent including foulants such as manganese.

Membrane filtration process is an advanced water treatment technology that has excellently removes turbidity and microorganisms. However, it is known that it has problems such as low economic efficiency and the operating stability. Therefore, this study was to evaluate on the economical feasibility and operational stability comparison of membrane and sand filtration process in Im-sil drinking water treatment plant. For the economic analysis of each process, the electricity cost and chemical consumption were compared. In the case of electric power consumption, electricity cost is 68.67KRW/㎥ for sand filtration and 79.98KRW/㎥ for membrane filtration, respectively. Therefore, membrane filtration process was about 16% higher than sand filtration process of electricity cost. While, the coagulant usage in the membrane filtration process was 43% lower than the sand filtration process. Thus, comparing the operation costs of the two processes, there is no significant difference in the operating cost of the membrane filtration process and the sand filtration process as 85.94KRW/m3 and 79.71KRW/m3 respectively (the sum of electricity and chemical cost). As a result of operating the membrane filtration process for 3 years including the winter season and the high turbidity period, the filtrated water turbidity was stable to less than 0.025 NTU irrespective of changes in the turbidity of raw water. And the CIP(Clean In Place) cycle turned out to be more than 1 year. Based on the results of this study, the membrane filtration process showed high performance of water quality, and it was also determined to have the economics and operation stability.

This study applied microbubbles to reduce membrane fouling in wastewater reuse membrane processes, evaluated and compared the transmembrane pressure with or without the application of microbubbles and the cleaning efficiency with the application of aeration and microbubbles. In addition, this study analyzed foulants removed from the membrane surface. Changes in the transmembrane pressure of membranes with the presence or absence of microbubbles were observed. As a result, transmembrane pressure (TMP) increasing rate decreased twofold when applying microbubbles to realize stable operations. This study compared and evaluated cleaning efficiency applying aeration and microbubbles. As a result, the cleaning efficiency was 5% higher on average when applying microbubbles. In turbidity and total organic carbon (TOC), foulants were discharged when applying microbubbles twice as much as applying aeration. It is thought that particulate foulants precipitated on the membrane surface were more likely to desorb because the adhesion between the membrane surface and particle was weakened by microbubbles. Therefore, it is considered possible to effectively control membrane fouling because of the increase in cleaning efficiency when applying microbubbles to wastewater reuse membrane processes.

최근 막여과 정수처리에 대한 관심이 높아지고 있으나, 공정설계를 위한 소프트웨어가 널리 보급되어 있지 않아서 현장적용의 어려움이 발생하고 있다. 본 연구에서는 막여과 정수처리 공정설계를 지원할 수 있는 프로그램과 설계기법을 개발하고자 하였다.

수온 상승에 따른 조류 등 이취미 물질의 증가, 미량 유해물질의 검출로 인해 기존 여과 공정으로 시민들의 수질 기대조건을 충족할 수 없기 때문에 오존+활 성탄 등의 고도정수처리 공정의 도입이 활성화되었으며, 이미 대도시, 광역단위 에는 고도정수처리 공정 도입이 완료된 상황이다. 대부분의 국내 정수장의 여과 공정은 급속 모래여과 공정으로 구성되어 있으며, 10년간 막여과 공정이 등장하여 여과 공정에 따른 후단 오존+활성탄 공정에 미치는 영향을 파악하는 것이 필요하다고 판단되었다. 서울시 Y 정수장에 설치된 고도정수처리 파일럿 플랜트 를 활용하여 고도정수처리 공정에 모래여과수와 막여과수가 유입되었을 경우 수질 및 제거율의 변화와 활성탄 표면 변화를 관찰하였고 이를 통해 막여과 정수처리 공정 도입 필요성을 검토하였다.

본 연구에서는 MF/UF/RO/MD와 같은 다양한 종류의 막여과 공정에 대하여 에너지 사용량을 분석하기 위한 기법을 개발하기 위하여 수행되었다. 에너지 흐름 분석을 위하여 공정모사 모델을 개발하였으며 이를 이용하여 각 단계별 유효에너지와 에너지 손실을 계산하였다.

Temperature correction trans-membrane pressure (TC-TMP) is frequently used as a fouling index in membrane water treatment plants. TC-TMP equation is derived based on an assumption that the total membrane resistance (i.e. the sum of the intrinsic membrane resistance and fouling resistance) is not affected by temperature. This work verified the validity of this assumption using microfiltration (MF) and ultrafiltration (UF) membranes with and without fouling. The foulants used in the work were kaolin (inorganic) and humic acid (organic). The intrinsic resistances of MF and UF membranes remains at constant values regardless of temperature change. When the same amount of foulants were accumulated on the membrane, inorganic fouling resistance with kaolin was constant regardless of temperature change while organic fouling resistance with humic acid decreased at higher temperatures, which means that TC-TMP cannot be used as a fouling index when organic fouling occurs in a real field application. Since TC-TMP underestimates the amount of fouling at higher temperatures, more attention should be necessary in the operation of membrane water treatment plant in a hotter season like summer.

본 연구는 잔류함으로써 문제를 일으킬 수 있는 응집제를 사용하지 않고 물리적인 처리만을 사용하는 막여과 정 수처리의 전처리로 F/A 공정을 구성하고자 하였고 이를 구성하는 여재의 성능을 연구하였다. 특히, 탁질 물질과 유기물 제거 가 가능한 것으로 알려진 Filtralite의 도입 가능성을 검토하였다. Filtralite의 탁도 제거효율은 원수대비 83~84%로 여과사와 비슷한 결과 값을 나타내었으며 여재표면에 잘 발달된 공극 때문에 유기물 제거능은 여과사보다 50% 더 높게 나타났다. 따 라서 F/A 공정을 구성함에 있어 여과사보다 Filtralite가 더 효율적이라 검토되었다. 활성탄과 연계한 F/A 공정을 구성하여 막 여과 처리 시스템의 전처리효율을 실험한 결과, TOC 농도는 TMP의 증가에 큰 영향을 주는 것으로 판단되어 막오염 저감에 유기물 제어가 중요함을 확인하였으며 유기물 제거 효율이 뛰어난 여재 사용이 필요할 것으로 판단되었다.

기존 정수처리 공정은 나날이 발현빈도 및 농도가 증가하고 있는 신규오염물질을 대처할 수 없는 실정이다. 이를 위하여 다양한 고도처리공정이 도입되고 있으며 이 중 막여과공정은 최근 설치비율이 급격하게 상승하고 있다. 본 연구에서는 망간이 발현되고 있는 U정수장을 대상으로 MF막을 설치한 파일롯 플랜트를 운영하여, 막여과공정에서의 화학세척조건에 따른 회복성능을 평가하고 이온분석을 실시하였다. 이는 망간발현지역을 대상으로 한 최적의 분리막 세척조건 도출을 위한 기초자료로 활용할 수 있다.

망간은 수중에서 대체적으로 불용성이나, 지하나 지표에서 여러 가지 반응으로 인해 수중으로 용존되어 유입된다. 용존된 망간은 먹는 물에서 0.1 mg/L 이상일 경우 불쾌한 금속냄새가 나며, 0.02 mg/L 이상에서는 박테리아에 의한 이취미가 발생할 수 있다. 또한, 망간산화물이 급배수관에 피복되어 통수능을 감소시킨다. 최근 강화된 국내 먹는 물 수질 기준치는 0.05 mg/L이다. 이러한 망간 문제를 해결할 수처리 공정 연구가 필요하다. 본 연구에서는 과망간산칼륨(KMnO4)과 차아염소산 나트륨(NaOCl)을 이용하여 망간을 산화물로 변화시키고, 이를 한외여과막으로 제거한 후의 망간제거효율을 연구하였다. 특히, 두 산화제를 복합으로 사용할 때의 효과를 분석하고 실제 적용 가능성을 타진하였다.

Various treatment system for residuals have applied to save water resources, but most of them were not be satisfied with legal standard consistently. In this study, submerged membrane treatment system was operated to treat water treatment plant residuals and operation parameters was evaluated. Result of this experiment, high concentration organic matters contributed to high increase Transmembrane pressure(TMP) of membrane system(from 0.05 bar to 0.35 bar). And backwash process was effective to stabilize membrane system operation. After Cleaning-In-Place(CIP), permeability was recovered about 100 % from first operation condition. Inorganic matters (Fe, Mn, Al, Ca, Mg) were not effective membrane filtration performance. The quality of residual treatment was satisfied with drinking water quality standard and a treated water from that system was suitable for water reuse.

가압식 MF공정의 전처리공정으로 침전지가 없는 혼화/응집공정에서 적정응집제 투입농도선정 및 유기물 제거성능을 평가하였다. 전처리 공정에서 생성된 플럭이 가압펌프의 임펠러에 의해 해체됨을 확인하였으며 원수탁도가 10 NTU 이하로 유입이 될 때, 혼화/응집조와 펌프후단에서 플럭형성을 위한 최적응집제 투입량은 4 mg/L (as PACl 17%)이었다. 이때의 DOC 제거율은 평균 43%이었으며, 응집제투입량을 계속적으로 증가시켜 8 mg/L (as PACl 17%)로 투입을 하였을 때, DOC 제거율은 평균 48%를 나타내어 제거율은 크게 개선되지 않았다. 전처리가 없는 PVDF 가압식 MF공정의 TMP는 0.54bar에서 운영이 되었으며, 혼화/응집 전처리 공정을 적용하여 운영 시 TMP는 0.41 bar로 안정적인 운영이 가능하였다.

현재 분리막 여과 공정은 정수처리에서 많은 관심을 받고 있다. 하지만, 분리막의 효율적인 운영을 위하여 '혼화/응집(/침전)' 등의 전처리 시설 설치로 인한 부지면적 및 비용증가와 5~10%의 배출수 문제가 추가적으로 발생한다. 그래서 본 연구에서는 전처리 공정 없이 지표수(한강)에 대하여 가압식 PVDF 분리막[(주)에코니티]으로 운전하여 성능을 검토하였으며 그 결과 1년 동안 화학적 세정 없이 여과 flux가 1~2.4 m/d (at 25℃)로 운전되었고, 유입원수의 탁도와 상관없이 분리막 처리수의 탁도는 0.05 NTU 이하로 안정되게 유지되었다. 또한, 회수율 제고를 위하여 1개월 동안 가압식 배출수(역세수 + 배수)를 침지식 PE 분리막[(주)에코니티]으로 연계하여 2단 막여과 운영을 한 결과 전체 공정 회수율을 99.5%까지 증가시킬 수 있었다.

섬진강 수계의 복류수를 대상으로 막여과 정수처리 공정 현장 적용성 평가를 위해 여과막의 공경에 따른 막오염도 예측 및 최적 응집제 주입농도 선정을 통해 파일롯플랜트 규모의 검증실험을 실시하였다. 막공경에 따른 막오염도 평가를 위한 여과저항 평가실험 결과, 0.1mum 와 0.01mum 여과막의 비가역적 여과저항 증가율은 각각 0.44×10 12/m2, 0.42×10 12/m2로 나타났으며, Flux-test 실험결과, 적정응집제 주입농도는 Jar-Test 실험결과에 비해 낮게 나타났다. 현장 적용성 평가를 위해 6개월 동안의 파일롯플랜트 운영을 수행하였다. 응집을 실시하지 않은 막여과공정은 여과유속 1.0~1.5m3/m2 day,응집을 실시한 막여과 공정은 여과유속 1.0~2.0m3/m2 day의 조건에서 운전한 결과 두 조건 모두 6개월 이상 막차압이 안정되게 유지되었다. 따라서 섬진강 수계의 복류수를 이용한 막여과 공정 운영에 있어 적정 여과유속으로 운전 시 응집제 사용 없이 안정적인 운전이 가능함을 알 수 있었다.