• 한국물환경학회지
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• 제31권5호
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• pp.523-532
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• 2015

Hydrocyclone is widely used in industry, for its simple design, high capacity, low maintenance and low operational cost. The objective of this study is to develop hydrocyclone coagulation and filtration system. The system is made of hydrocyclone ballasted coagulation with polyaluminium chloride silicate (PACS) and upflow filter to treat micro particles in urban storm runoff. Roadside sediment particles (< $200{\mu}m$) was mixed with tap water to make various turbid suspensions to simulate urban storm runoff. The filter cartridge was filled with polyethylene media system and ran 1hr per everyday and total operation time were 8.19hrs and backwashing everyday after end of operation. The operation condition of flowrate was $8.2{\sim}11.9m^3/day$ (mean $10.1m^3/day$) and surface overflow rate (SOR) based on filter surface area was $45.5{\sim}65.9m^3/m^2/day$ (mean $55.7m^3/m^2/day$). The range of PACS dosage concentration was 14.0~31.5 mg/L. As the results of operation, the range of removal efficiency of turbidity, SS were 81.0~95.8% (mean 89.5%) 81.8~99.0% (mean 91.4%), respectively. An increase of filtration basin retention time brought on increased of removal efficiency of turbidity and SS, and increase of SOR brought on decreased of removal efficiency. During the first flush in urban area, storm runoff have an high concentration of SS (200~600 mg/L) and the filtration bed becomes clogged and decreased of removal efficiency. Backwashing begins when the drainage pipe valve at the filtration tank bottom is completely open (backwashing stage 1). Backwashing stage 2 was using air bubbles and water jet washing the media for 5 mins and open the drainage valve. After backwashing stage 1, 2, 61.83~64.04%, 18.53~27.51% of SS loading was discharged from filtration tank, respectively. Discharged SS loading from effluent was 7.12~14.79% and the range of residual SS loading in fliter was 2.26~5.00%. The backwashing effects for turbidity, SS were 89.5%, 91.4%, respectively. The hydrocyclone coagulation and filtration with backwashing system, which came out to solve the problems of the costly exchange filter media, and low efficiency of removing micro particles of filter type nonpoint treatment devices, is considered as an alternative system.

• 한국물환경학회지
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• 제23권6호
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• pp.920-926
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• 2007

The upflow Biobead$^{(R)}$ process, one of biological aerated filters (BAF), which was used commercially, invented for removal of organic materials and nitrification. This process was modified to enhance the ability of denitrification through the induction of pre-anoxic tank. In this research, we investigated the effects of hydraulic retention time (HRT) and backwashing period in aerobic tank. The characteristics of nitrifying bacteria, which are composed of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), also investigated using fluorescence in situ hybridization (FISH). Even though the HRT was shortened, the efficiency of nitrification was not decreased when the organic loading rate and ammonium-nitrogen loading rate were $2.10kg/m^3/day$ and $0.25kg/m^3/day$, respectively. And then the distribution ratios of AOB and NOB showed the similar patterns. However, when the backwashing period was lengthened from 12 hours to 24 hours in aerobic 1 tank, the nitrification efficiency was decreased to 63.9% from 89.2%. The results of FISH explained that this decrease of nitrification efficiency was caused by the decrease of distribution ratio of AOB in aerobic 1 tank. The nitrification efficiencies of aerobic 1 and aerobic 2 tank were increased when the backwashing period was lengthened because of relative high distribution ratios of nitrifying bacteria.

• 한국수자원학회논문집
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• 제35권2호
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• pp.213-220
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• 2002

하수 처리수의 재이용을 위하여 표준활성슬러지법에 의한 생물학적 처리 후 최종침전지 유출수를 급속여과공정으로 처리하기 위한 Pilot Plant 실험연구가 수행되었다. 또한, 활성슬러지와 연계된 급속여과공정과 포기조 후단에 응집제를 주입하는 활성슬러지 이후 급속여과 처리하는 공정과의 비교 실험도 행해졌다. 최종침전지 유출수를 급속여과공정으로 처리한 경우 여과속도는 100m/day, 여과지속시간은 40시간 이하로 운전하는 것이 타당한 것으로 나타났으며, 여과지의 역세척 주기는 여과속도 100m/day일 때 40시간에 1회 정도가 되었다. 여과지 역세척 시 역세척 방법은 공세 1분, 공세+수세 30초, 수세 1분, 공세·수세 2분, 수세 3분, 안정 30초, 배수 10분의 순으로 행하는 것이 효과적이었으며, 수세속도는 10LPM으로 전체 여과수량의 2%정도였다. 표준활성슬러지 시스템에 의한 2차 처리수를 잡용수로 재이용 하기 위해서는 폭기조 후단에 응집제를 첨가하여 여과 공정을 후속공정으로 하는 시스템으로 유용하게 사용할 수 있을 것으로 판단된다.

• 상하수도학회지
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• 제13권2호
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• pp.41-46
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• 1999

Backwashing is an important process for the efficient operation of granular filters, and the efficiency of the surface washing among the backwashing processes can affect the filtrations rate and filter run-time. In this study, the efficiency of surface washing is evaluated using real filters for three cases: with surface washing (with and without drainage of water to the surface of filter bed) and without surface washing. As a result, in the case of adopting both the drainage and surface washing, the filter of which condition is initially worse than those of the other filters shows improvement in head-loss development, filtration velocity, filter run-time, and total filtration volume. On the other hand, the conventional method of surface washing rarely has an effect on the filter washing.

• 상하수도학회지
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• 제10권2호
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• pp.70-79
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• 1996

Ultrafiltration(UF) and powdered activated carbon(PAC) adsorption were combined to treat wastewater contaminated with refractory organic compounds. Secondary sewage effluent of RBC process was used for the investigation. It was determined from batch test results that a contact time of 2 hours and a PAC dose of 450mg/l would be used in the experiments. Backwashing was accomplished by forcing the permeates back ward with pressure of $2.5kgf/m^2$ for 90 seconds. It was shown that refractory organics removal by the PAC-UF process was more efficient than UF process without PAC pretreatments. As backwashing frequency was decreased from four times to one time in an hour, the removal efficiency was significantly increased. The addition of PAC to the UF process mitigated the fluctuation of filtrate quality which was increased in UF process without PAC treatment as transmembrane pressure was increased.

• 대한환경공학회지
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• 제28권3호
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• pp.276-285
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• 2006

오염 하천수 수질개선 연구를 위해 pilot plant 규모의 호기성 생물여과 공정을 이용하여 실제원수를 적용한 경우 유입 공기량을 $0.1m^3air/m^2min$으로 고정하고 EBCT를 90, 60, 45, 30 min으로 운전 시 입자성 물질(SS, Turbidity, Chl.-a)의 경우 EBCT와 관계없이 80% 이상의 처리효율을 나타냈으며 암모니아성 질소의 경우 85% 이상의 처리효율을 보였다. BOD의 경우 하천수수질 환경기준 III-IV 급수로 유입되어 I 급수 미만으로 유출되 본 처리 공법 사용 시 생물학적 안정성을 충분히 확보할 수 있을 것으로 판단되었다. $COD_{Mn}$의 경우 약 60%의 제거효율을 보여 BOD 제거율에 비해 효율이 저하되는 것으로 나타났는데 이러한 원인을 규명한 결과 전체 COD 물질 중 30% 정도가 반응기 내부에 clogging된 조류에 의해서 발생되는 것으로 조사되었으며 이들 조류기원성 유기물들의 기질 비 소비율이 $0.0245mg{\cdot}COD_{Mn}/mg{\cdot}VSS{\cdot}day$로 생물학적 분해가 거의 되지 않는 것으로 나타나 이에 대한 대책으로 부분역세(partial backwashing)에 대한 필요성이 요구되었다. 이에 부분역세(상부 1 m 여재에 대한 1일 1회 역세)를 통해 BOD 5.5%, $COD_{Mn}$ 10% 정도의 제거율 상승을 얻을 수 있었고 이를 통해 생물학적으로 좀더 안정된 원수 확보가 가능해졌으며 역세 기간의 연장으로 역세수 절감 및 유량 확보 효과를 가져 올 것으로 판단된다.

• 멤브레인
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• 제24권5호
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• pp.393-399
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• 2014

본 연구에서는 디스크 링 형태에 패터닝된 박막을 적층시킨 모듈의 분리특성을 규명하고자 투과실험을 수행하였다. 먼저, 본 연구에서 자체 제작한 5가지 형태의 디스크 필터의 순수 투과도를 측정하였으며 그 값은 0.25 내지 $2.24L/m^2{\cdot}hr{\cdot}bar$이었다. 0.1 wt% 카올린 수용액을 투과시키면 순수 투과율이 가장 높은 모듈의 투과유속이 가장 높았고, 순수 투과율이 가장 낮았던 모듈의 카올린 투과유속이 가장 낮게 나타났다. 그러나 모든 모듈의 카올린 투과유속이 순수 투과율에 비례하지는 않았다. 또한 0.1 wt% 수용액으로 장시간 운전하기 위하여 디스크 필터 모듈 1에 주기적으로 역세척을 실시하였으며 가장 효율적인 운전조건은 투과시간 8분, 역세척 2분 주기임을 확인하였다.

• 한국물환경학회지
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• 제18권3호
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• pp.253-260
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• 2002

The purpose of this research was to describe the mechanisms and prevention of initial degradation in turbidity of the sand filter effluent. The method used was by adding a coagulant (PAC) to the sand filter after backwashing as a means of reducing turbidity. It was found that adding 80 mg/L of PAC solution to the sand filter was very effective in improving the initial effluent turbidity. A turbidity removal efficiency of 99 % was observed in the initial term period as compared to a 70% efficiency without PAC addition. The PAC solution added to the sand filter resulted in high aluminum concentration at the upper layer as compared with the bottom layer of the sand filter column. A change in the zeta potential to a strong positive-ions at upper layer was observed at this time but only a small change was obtained at the bottom. This result showed that the zeta potential of the sand was changed to positive with PAC coating. The effect of pH on zeta potential with PAC addition was also investigated. Zeta potential was greatly changed to positive-ion at pH 4~6. A series of experiments was then conducted in this study to optimize the pH of the PAC solution to be added to the sand filter after backwashing. The removal efficiency of turbidity was found to be highest at pH 5. This result suggested that hydrolyzed aluminium species attached to the surface of the sand enhanced the removal of turbidity of the effluent.

• 상하수도학회지
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• 제31권5호
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• pp.389-395
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• 2017

In this paper, we investigate the characteristics of membrane fouling caused by water temperature in the Membrane bioreactor(MBR) process and try to derive the membrane fouling control by chemical enhanced backwashing(CEB). The extracellular polymeric substances(EPS) concentration was analyzed according to the water temperature in the MBR, and the membrane fouling characteristics were investigated according to the conditions, with sludge & without sludge, through a lab-scale reactor. As shown in the existing literature the fouling resistance rate was increased within sludge with the water temperature was lowered. However, in the lab-scale test using the synthetic wastewater, the fouling resistance increased with the water temperature. This is because that the protein of the EPS was more easily adsorbed on the membrane surface due to the increase of entropy due to the structural rearrangement of the protein inside the protein as the water temperature increases. In order to control membrane fouling, we tried to derive the cleaning characteristics of CEB by using sodium hypochlorite(NaOCl). We selected the condition with the chemicals and the retention time, and the higher the water temperature and the chemical concentration are the higher the efficiencies. It is considered that the increasing temperature accelerated the chemical reaction such as protein peptide binding and hydrolysis, so that the attached proteinaceous structure was dissolved and the frequency of the reaction collision with the protein with the chemical agent becomes higher. These results suggest that the MBRs operation focus on the fouling control of cake layer on membrane surface in low temperatures. On the other hand, the higher the water temperature is the more the operation strategies of fouling control by soluble EPS adsorption are needed.

• 멤브레인
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• 제25권3호
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• pp.276-286
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• 2015

30 LMH의 정유량 플럭스로 운전하는 MBR에서, 휴지 및 역세정에 따른 한외여과 분리막의 오염을 조사하였다. 또한, 연속적인 공기세정과 비교하여 분리막 여과저항을 최소화하기 위한 간헐적인 공기세정을 평가하였다. 여과 조건은 14.5분 여과와 0.5분의 휴지를 유지하였으며, 역세정 시간은 휴지 시간과 동일하게 운전하였다. 공기세정이 정지하는 동안에 분리막 표면의 겔층 위에 케?이 빠르게 축척되었으며, 역세정으로 겔층과 케?층의 복합층은 쉽게 제거되었다. 역세정 후에 공기세정이 정지하는 동안 분리막 표면에 케?이 형성되어 공경 내부의 오염현상을 억제하였다. Pearson 상관성을 조사한 결과, 간헐적인 공기세정에서 공기 세정이 정지하는 시간과 분리막의 오염은 매우 연관성이 높다는 것을 알았다. 즉, 간헐적인 세정에서 공기세정이 정지하는 시간이 갈수록 오염억제에 효과적이었다.