• 청정기술
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• 제23권1호
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• pp.34-41
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• 2017

스크러버는 적정한 처리효율을 유지하기 위하여 세정수를 지속적으로 교체해 주어야 한다. 하지만 화학업종 대부분은 폐수 처리시설이 없어 스크러버 세정수를 위탁 처리하고 있으며, 처리비용 때문에 자주 교체해 주지 못하는 실정이다. 이로 인해 악취배출허용기준을 초과하거나 배출구 농도가 더 높아지는 역전현상을 유발하기도 한다. 이에 세정수를 자체 정화 하여 사용할 수 있도록 여과와 흡착 공정으로 구성된 세정수 처리시스템을 개발하였다. 세정수 처리 시스템은 화학업종 두 개 스크러버를 대상으로 적용하였으며, 세정수 수질 상태와 악취저감 효과를 평가하였다. 세정수 처리 시스템 적용 결과 50% 이상의 수질개선 효과와 20% 이상의 악취개선 효과를 확인 하였으며, 기존 운영대비 40%의 비용절감 효과도 기대할 수 있었다.

• Membrane and Water Treatment
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• 제8권2호
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• pp.113-123
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• 2017

This study investigated effects of physical and chemical cleaning methods on the initial flux recovery of fouled membrane in membrane distillation process. A laboratory scale direct contact membrane distillation (DCMD) experiment was performed to treat digested livestock wastewater with 3.89 mg/L suspended solids, 874.7 mg/L COD, 543.7 mg/L nitrogen, 15.6 mg/L total phosphorus, and pH of 8.6. A hydrophobic PVDF membrane with an average pore size of $0.22{\mu}m$ and a porosity of 75 % was installed inside a direct contact type membrane distillation module. The temperature difference between feed and permeate side was maintained at $40^{\circ}C$ with the feed and permeate stream velocity of 0.18 m/s. The results showed that the permeate flux decreased from $22.1L{\cdot}m^{-2}{\cdot}hr^{-1}$ to $19.0L{\cdot}m^{-2}{\cdot}hr^{-1}$ after 75 hours of distillation. The fouled membrane was cleaned first by physical flushing and consecutively by chemicals with NaOCl and citric acid. After the physical cleaning the flux was recovered to 92 % as compared with the initial clean water flux of the virgin membrane. Then 94 % of the flux was recovered after cleaning by 2,000 ppm NaOCl for 90 minutes and finally 97 % of flux recovered after 3 % citric acid for 90 minutes. SEM-EDS and FT-IR analysis results presented that the foulants on the membrane surface were removed effectively after each cleaning step. The contact angle measurement showed that the hydrophobicity of the membrane surface was also restored gradually after each cleaning step to reach nearly the same hydrophobicity level as the virgin membrane.

• 한국도로학회논문집
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• 제9권3호
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• pp.75-82
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• 2007

터널 내 축적된 다양한 오염원들은 간헐적으로 수행되는 세척과정 중에 폐수로 배출되게 되며, 서울 시내 3개 터널 지점에서 수행된 수질분석결과 SS, $COD_{Cr}$, T-N, $NH_3-N$, $NO_3-N$, Zn, Cu, Cr(+6). Mn, Mg, Phenol. $CN^-$, E-Coli 등이 고농도 형태로 배출되는 것으로 나타났다. 한편, 이러한 오염수질의 배출농도 특성은 터널 세척 폐수의 채취 방법, 세척횟수, 세척수량, 터널내벽 특성, 통행량, 배수 특성 등에 따라 다양한 농도범위를 보여주는 것으로 나타났다. 한편, 수집된 터널 세척폐수를 단순 중력침전을 이용하여 저감실험을 수행한 결과, $COD_{Cr}$는 80%, T-N, T-P는 각각 30, 90% 제거됨을 확인하였고, 중력침전 분리를 통하여 제거되지 않은 잔여 오염물질에 대하여 GAC 소재를 통한 흡착실험(터널 세척폐수 $1{\ell}$에 대하여 GAC를 50g을 투입) 결과, $COD_{Cr}$, T-N, Zn, Cu, Mn, Phenol, CN 항목에서 80% 이상 제거됨을 확인하였다.

• 상하수도학회지
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• 제19권2호
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• pp.149-154
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• 2005

Conventionally used flocculation tanks require large space and high energy requirement for mixing. Static flocculators using gravel bed filter operate at a lower flow rate ($5-10m^3/m^2{\cdot}h$). Further, the cleaning of this system is difficult. A novel high rate static flocculator/filter developed at UTS packed with buoyant media such as polystyrene, polypropylene has been found to operate at higher filtration rates (30-45 $5-10m^3/m^2{\cdot}h$). They can easily be cleaned with minimal energy. Detailed experiments conducted with an artificial kaolin clay solution show that buoyant media is an excellent static flocculator in producing uniform filterable microflocs (12-15 m) even when it is operated at a high rate of 30-40 m/h. Detailed filtration experiments were conducted in a wastewater treatment plant to treat the biologically treated effluent with a floating media of depth of 120 cm. This filter was able to remove majority of phosphorus and remaining solids. It reduced significantly the fecal coliforms and fecal streptoccoci, thus requiring less amount of chlorine for disinfection. The advantage of this system is the low energy and water requirement for cleaning of filter bed. The periodic backwash adopted 30 seconds air and water and 30 seconds water cleaning every 90 minutes filter operation. Thisis equivalent to 1-2% of filtered water production. Mechanical cleaning system on the other hand, requires very low energy requirement (<1% of filtered water production).

• Korean Chemical Engineering Research
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• 제43권4호
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• pp.487-494
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• 2005

자동차, 기계금속, 전자 등 여러 산업에서는 부품 가공 중의 세정 과정에서 금속가공유와 각종 세정첨가물이 함유된 많은 폐수를 발생시킨다. 본 연구에서는 수용성 또는 비수용성 금속가공유로 오염된 수계 및 준수계 세정폐수를 한외여과막시스템을 이용하여 처리하고자 하였다. 이 실험에서 막을 친수성인 polyacrylonitrile(PAN)을 사용하고 막의 크기 및 오염물의 농도 변화에 따른 한외여과막 투과수량과 유수분리 성능(COD제거율)을 측정하여 한외여과법 처리의 적정성 여부를 조사 분석하였다. 그 결과 수계 또는 준수계세정제와 수용성 가공유로 오염된 가공폐수의 경우 한외여과막의 크기가 10 kDa에서 100 kDa로 증가함에 따라 COD 제거율은 90 wt％-95 wt％로 거의 일정하지만 투과플럭스는 4배 이상 증가하였다. 그리고 금속가공폐수의 오염물 농도가 3 wt％에서 10 wt％로 증가할수록 한외여과막의 COD 제거율은 증가하지만 투과플럭스는 감소하였다. 그러나 수계 또는 준수계세정제와 비수용성 오일로 오염된 가공폐수의 경우 오염물의 농도가 증가할수록 COD 제거율은 거의 일정하지만 투과플럭스는 급격히 감소함을 보여 주었다. 이러한 현상은 한외여과막 재질이 친수성인 PAN이기 때문에 비수용성 오일이 막을 통과하지 못하고 막의 기공을 막기 때문인 것으로 추론된다. 따라서, 수용성 오일이 함유된 세정액은 막재질이 PAN이고 세공크기가 100 kDa인 한외여과법 처리가 적정한 것으로 판단되었다. 이러한 기초실험 결과를 활용하여 PAN 재질의 막(MWCO=100 kDa)을 사용한 한외여과 pilot 시스템을 설치 운전하여 수용성 인발유로 오염된 알칼리 세정 폐액을 처리하고 알칼리세정제와 인발유를 재활용하고자 하였다. 현장 실험 결과 한외여과 공정은 수계세정제와 수용성오일을 효과적으로 분리하여 재활용할 수 있었고 기존 공정에 비하여 세정제 사용수명을 12배 이상 증가시킬 수 있었다.

• 상하수도학회지
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• 제13권1호
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• pp.140-145
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• 1999

This study was carried out a investigate the effect of chemical cleaning of corrosion product in cooling system made of copper and copper alloy as basic material and used cooling water as pure water. We studied chemical cleaning condition that minimizes the influence on basic material by means of EDTA solution so as to eliminate the slurry in cooling system. As a result, we found that the main components of sludge in cooling system produced by corrosion of copper were $Cu_2O$, CuO, Cu, and Fe. The optimum condition of chemical cleaning was 400 ppm EDTA solution at $60^{\circ}C$.

• 상하수도학회지
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• 제25권3호
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• pp.285-291
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• 2011

Membrane fouling is an unavoidable phenomenon and major obstacle in the economic and efficient operation under sea water reverse osmosis (SWRO). When fouling occurs on the membrane surface, the permeate quantity and quality decrease, the trans-membrane pressure (TMP) and operation costs increase, and the membrane may be damaged. Therefore, chemical cleaning process is important to prevent permeate flow from decreasing in RO membrane filtration process. This study focused on proper chemical cleaning condition for Shuaibah RO plant in Saudi Arabia. Several chemical agents were used for chemical cleaning at different contact time and concentrations of chemicals. Also autopsy analysis was performed using LOI, FT-IR, FEEM, SEM and EDX for assessment of fouling. Specially, FEEM analysis method was thought as analyzing and evaluating tool available for selection of the first applied chemical cleaning dose to predict potential organic fouling. Also, cleaning time should be considered by the condition of RO membrane process since the cleaning time depends on the membrane fouling rate. If the fouling exceeds chemical cleaning guideline, to perfectly remove the fouling, certainly, the chemical cleaning is increased with membrane fouling rate influenced by raw water properties, pre-treatment condition and the point of the chemical cleaning operation time. Also choice of cleaning chemicals applied firstly is important.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.360-360
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• 2008

Steelmaking industry is widely known to use a lot of water and same amount of wastewater is generated. Although toxicity of wastewater from Steelmaking industry is low, it contains an amount of various organic materials and Fe-Oxides. It is important to recycle the wastewater because of water shortages and water pollution. In general, large-scale equipment is necessary to process the wastewater. On the other hand, superconducting high gradient magnetic separation (HGMS) system can process the wastewater in the small space. Superconducting HGMS system that had a purpose to purify the wastewater was assembled. Cryo-cooled Nb-Ti superconducting magnet was used for magnetic separator. This system can operate continuously because contaminated filters can keep on returning after cleaning. The various magnetic seeding reactions were investigated to increase the reactivity of coagulation. Filter cleaning system was developed to decrease the quantity of clean water. This research was supported by a grant from Korea Electrotechnology Research Institute, Republic of Korea.

• 상하수도학회지
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• 제31권3호
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• pp.229-236
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• 2017

In this study, a direct contact membrane module was manufactured to be used in a pilot scale membrane distillation process to treat $3m^3/day$ of the digestate produced from anaerobic digestion of livestock manure. In order to investigate the performance of the membrane module, permeate flux was measured with and without spacer inside the module under various condition of temperature difference and cross flow velocity (CFV) through the membrane surfaces. Flux recovery rate after chemical cleaning was also investigated by applying three different cleaning methods. Additionally, thermal energy consumption was theoretically simulated based on actual pilot plant operation conditions. As results, we observed flux of the module with spacer was almost similar to the theoretically predicted value because the installation of spacer reduced the channeling effect inside the module. Under the same operating condition, the permeate flux also increased with increasing temperature difference and CFV. As a result of chemical in-line cleaning using NaOCl and citric acid for the fouled membranes, the recovery rate was 83.7% compared to the initial flux when NaOCl was used alone, and 87% recovery rate was observed when only citric acid was used. However, in the case of using only citric acid, the permeate flux was decreased at a rapid rate. It seemed that a cleaning by NaOCl was more effective to recover the flux of membrane contaminated by the organic matter as compared to a cleaning by citric acid. The total heat energy consumption increased with increasing CFV and temperature difference across the membrane. Thus, further studies should be intensively conducted to obtain a high permeate flux while keeping the energy consumption to a minimum for a practical application of membrane distillation process to treat wastewater.

• 상하수도학회지
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• 제34권4호
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• pp.267-276
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• 2020

In this study, air scouring cleaning was selected and applied among 5 small blocks (S1~S5) in domestic S cities to analyze the cleaning effect of particles causing discoloration. In order to identify the cleaning effect, 10 locations were selected as water quality investigation point, such as the stagnant or water mains ends. Removal of solids, variation of particle components, weight and concentration were analyzed. And the level of the cleanness of the surface inside water mains using endoscope was investigated. As a result of analysis, the solids discharged after cleaning were mainly sand and gravel, pieces related to pipe materials, and corrosion products. As a result of analyzing the concentrated particles of the filter before and after cleaning, it was found that the change in discoloration on the filter was large. In addition, as a result of comparing the weight and the concentration of the particles, it was found that the particles causing discoloration were significantly removed after cleaning. From the results of the endoscopy, it was confirmed that most of the precipitated and accumulated dark yellow discoloration matters inside water mains were removed through cleaning. Therefore, it seems that the particles causing discoloration in water decreased after cleaning. Therefore, it is expected that, if properly cleaning was applied, matters that cause discoloration can be removed from the water mains, and customer's complaints can also be reduced through water quality improvement.