In order to determine the location of average concentration and distribution status of dissolved oxygen in the rectangular aeration tank of the sewage treatment plant was analyzed and the difference of dissolved oxygen concentration was remarkable at each location. Compared with the computational fluid dynamics analysis, it was found that the results were consistent with the measurement results by showing the difference of dissolved oxygen concentration between the locations. Based on the measured data, the representative location of dissolved oxygen in aeration tank was selected by using statistical analysis method and the representative location was expressed in three-dimensional coordinates(LWH : 25%, 50%, 33%) from flow direction and left wall. Also the difference between the dissolved oxygen concentration at the actual measurement location and the average concentration value of the entire aeration tank was founded, and the equations for calibrating the automatic measurement data considering the actual measurement location were calculated.

In this study, the fate and removal of 15 pharmaceuticals (including stimulants, non-steroidal anti-inflammatory drugs, antibiotics, etc.) in unit processes of a sewage treatment plant (STP) were investigated. Mass loads of pharmaceuticals were 2,598 g/d in the influent, 2,745 g/d in the primary effluent, 143 g/d in the secondary effluent, and 134 g/d in the effluent. The mass loads were reduced by 95% in the biological treatment process, but total phosphorous treatment did not show a significant effect on the removal of most pharmaceuticals. Also, mass balance analysis was performed to evaluate removal characteristics of pharmaceuticals in the biological treatment process. Acetaminophen, caffeine, acetylsalicylic acid, cefradine, and naproxen were efficiently removed in the biological treatment process mainly due to biodegradation. Removal efficiencies of gemfibrozil, ofloxacin, and ciprofloxacin were not high, but their removal was related to sorption onto sludge. This study provides useful information on understanding removal characteristics of pharmaceuticals in unit processes in the STP.

The purpose of this study was to analyze water treatment characteristics, including the efficiency of removing algae from water purification plants, by installing a demonstration facility for decontamination of algae, including natural algae remover injection equipment, in the water purification plant. Jar-test showed that the optimum injection of natural decontaminant was 20 mg/L. Of the water contaminant treatment efficiency of the intake and water purification plants, Chl-a averaged 74.0% elimination efficiency from 5.0 mg/m3 to 1.3 mg/m3 and the maximum treatment efficiency was 91.5% removal efficiency when the inflow concentration of Chl-a was 11.8 mg/m3. In addition, 51.2% and 47.1% of the taste and odor indicator items, geosmin and 2-MIB, resulted from the overgrowth and decaying of algae, respectively, to identify toxic substances and odor reduction effects. In addition, elimination efficiencies of SS and Turbidity materials were higher than 70.0%. In the injection of natural algae remover, no effects such as sudden changes in water quality due to secondary reactions were found, and appropriate levels were maintained under water treatment conditions.

본 사례는 최근 준공된 “구미하수처리장 하수처리수를 이용한 재이용시설”에 대한 것으로 이 시설은 구미하수처리장의 2차 처리수를 원수로, 응집침전시설, 전처리시설, 주처리시설과 재이용수 공급시설로 구성되어 있으며, 설비의 성능 확인을 위한 시운전을 완료하였다. 주처리시설로는 역삼투막(RO Membrane)을 적용하였으며, 하수처리수 내 잔류물질로 인한 역삼투막 성능저하방지와 수요처의 요구수질 충족을 위해 활성탄 주입을 포함한 응집침전공정과 정밀여과막(Micro Filter)을 전처리시설로 구성하였다. 사업 초기단계에 현재 시공된 것과 동일한 공정으로 구성된 Pilot Plant를 건설, 운영하여, 반영된 각 단계별 공정의 적정성과 주요 설계 인자를 확인하였으며, 일부 확인된 개선 사항은 실시설계시 반영하였다.

막여과 정수장에 고농도 망간이 유입될 경우 심각한 막오염을 유발할 수 있어 망간에 대한 제어가 필요하다. 최근 수처리제로 등록된 NaMnO4의 경우 짧은 반응시간에 망간 제거가 가능하여 정수장 적용이 유리할 것으로 기대되고 있다. 본 연구에서는 NaMnO4 주입에 따른 망간 제거 성능과 막의 여과유속에 미치는 영향을 평가하였다. 유입망간농도 대비 NaMnO4 주입 조건을 평가한 결과반응시간 5분 이내 1배, 1.5배 조건에서 약 90% 이상의 망간 제거 효율을 나타내었으며 0.5배, 2배 조건에서는 제거효율이 감소되었다. 또한, NaMnO4 주입조건과 미주입 조건에 대한 여과유속을 평가한 결과 미주입 조건과 비교하여 주입조건에서의 막오염이 저감되어 미주입 조건과 비교하여 유과유속이 높게 유지되었다.

The problem of disposal of brine due to increased MD/RO desalination plant has recently become a big social issue. The chlor-alkali process through electrolysis of brine has been studied as a method to overcome this problem. In order to increase the electrolysis efficiency, a pretreatment process for removal of hard substances must be preceded. In this study, we investigated the mechanism of removal of hardness through chemical precipitation. As a result, Ca was greatly influenced by addition of Na2CO3, and Mg was strongly influenced by pH. Also, the addition of NaOH and Na2CO3 enabled simultaneous removal of Ca and Mg, and showed a removal efficiency of 99.9% or more. Finally, the residual concentrations of Ca and Mg in the brine after the reaction were 0.14 and 0.13 mg/L, respectively. Saturation index was calculated using Visual MINTEQ 3.1, and solid phase analysis of the precipitate was performed by FE-SEM and PXRD analysis. It was confirmed that precipitate formed by the formation of calcite and brucite.

Modified coagulants were investigated for the removal of phosphorus from secondary effluent of wastewater treatment. The modified coagulants were prepared by mixing alkali earth metal ions such as calcium and magnesium. The basicity of a coagulant influenced on the removal of phosphorus, and coagulants with basicity of 5.9% showed a better removal of total phosphorus than that of 38.5%. Also, coagulants with alkali earth metals enhanced the performance of coagulation by 10% and resulted in 67.1% for total phosphorus removal. Moreover, the removal of suspended solids and chemical oxygen demand was improved using coagulants with low basicity and earth metal ions. Results of this study demonstrated that the use of coagulants with low basicity, and calcium and magnesium ions is recommended to improve wastewater effluent quality.

This study was performed to improve the foaming generated in the effluent of wastewater treatment plant from March 2015 to July 2016. The main cause of foaming was air entrainment by an impinging jet and the internal accumulation by the diffusion barrier. Particularly, the foam growth was most active when there is low tide and larger discharge. To solve this problem, we experimented after installing fine mesh screen and the artificial channel device with underwater discharging outlet in the treated wastewater discharge channel and the outlet, respectively. As a result, the effects of foam reduction by devices ranged 85.0~92.0% and 70.7~85.6%, respectively. In addition, the foam and the noise were easily solved, first of all look to contribute to the prevention of complaints. Our device studies were applied to a single wastewater treatment plant. However, it is considered to be able to apply in other similar cases of domestic sewage treatment plants.

Pollutants removal and disinfection effect of secondary effluent from final settling tank of sewage treatment plant of W city were investigated in Loop Reactor using ordinary granular activated carbon(GAC) and GAC coated with silver nanoparticles. The results showed that the removal efficiency of CODMn, T-N and T-P using GAC with silver nanoparticles were higher than using the ordinary GAC. The removal efficiency of T-P using GAC with silver nanoparticles is 45.4% and that of T-P using ordinary GAC is 30.9% in the same case of the input amount of 20 g/L of GAC. The total califorms is reduced according to increasing input amount of GAC with silver nanoparticles and ordinary GAC. The disinfection efficiency of total coliforms in case of GAC with silver nanoparticles is much higher than that in case of ordinary GAC. For all experiments using the silver nanoparticles, the total coliforms is under 26 cfu/mL and this shows very excellent disinfection effect.

Peak load rate(i.e., maximum daily flow/average daily flow) has not been considered for industrial water demand planning in Korea to date, while area unit method based on average daily flow has been applied to decide capacity of industrial water treatment plants(WTPs). Designers of industrial WTPs has assumed that peak load would not exist if operation rate of factories in industrial sites were close to 100%. However, peak load rates were calculated as 1.10~2.53 based on daily water flow from 2009 to 2014 for 9 industrial WTPs which have been operated more than 9 years(9-38 years). Furthermore, average operation rates of 9 industrial WTPs was less than 70% which means current area unit method has tendency to overestimate water demand. Therefore, it is not reasonable to consider peak load for the calculation of water demand under current area unit method application to prevent overestimation. However, for the precise future industrial water demand calculation more precise data gathering for average daily flow and consideration of peak load rate are recommended.

This study was conducted to suggest the cause analysis and mitigation measures of foaming generated in the effluent of wastewater treatment plant. The foam generated in the outlet connected with the tidal river system was identified as structural problems. And the main cause of foaming was air entrainment by an impinging jet and the internal accumulation by the diffusion barrier. In consideration of these conditions, it present the effective ways such as micro-screen and submerged outlet, to mitigate the foaming generated in the water channel and outlet end.

This study has implemented an experiment in which hydrogen sulfide was removed by establishing a two-stage packed tower effector filled with nutritious medium and also filling a tower that was immobilized in ceramic media after isolating and identifying the sulfur oxidizing bacteria from a sewage treatment plant. As a result, strains isolated from the sewage treatment plant were found to be similar, including Bacillus fusiformis, Bacillus anthracis sp., Paenibacillus sp., Serratia marcescens sp., Bacillus thuringiensis. The effector that immobilized isolated strains in the ceramic media achieved an approximately 90% removal rate of hydrogen sulfide, while the sterilized ceramic media not immobilized with isolated strains showed a removal rate of about 65%. In addition, the removal rate of hydrogen sulfide in the primary media packing effector immobilized with sulfur oxidizing bacteria was about 92%, while the secondary effector filled with medium had a hydrogen sulfide removal rate near 100%. In addition, 90% efficiency of removal was shown in conditions of EBCT 60s in the experiment that investigated removal rate of hydrogen sulfide according to residence-time, while the efficiency was rapidly reduced up to 45% in conditions of EBCT 30s. On the other hand, when operating for an extended period time while increasing the concentration of injected hydrogen sulfide, the amount of sulfate was increased from 2 mg/L to 12.7 mg/L, and pH was rapidly reduced to 2.7.

This study has implemented an experiment in which hydrogen sulfide was removed by establishing a two-stage packed tower effector filled with nutritious medium and also filling a tower that was immobilized in ceramic media after isolating and identifying the sulfur oxidizing bacteria from a sewage treatment plant. As a result, strains isolated from the sewage treatment plant were found to be similar, including Bacillus fusiformis, Bacillus anthracis sp., Paenibacillus sp., Serratia marcescens sp., Bacillus thuringiensis. The effector that immobilized isolated strains in the ceramic media achieved an approximately 90% removal rate of hydrogen sulfide, while the sterilized ceramic media not immobilized with isolated strains showed a removal rate of about 65%. In addition, the removal rate of hydrogen sulfide in the primary media packing effector immobilized with sulfur oxidizing bacteria was about 92%, while the secondary effector filled with medium had a hydrogen sulfide removal rate near 100%. In addition, 90% efficiency of removal was shown in conditions of EBCT 60s in the experiment that investigated removal rate of hydrogen sulfide according to residence-time, while the efficiency was rapidly reduced up to 45% in conditions of EBCT 30s. On the other hand, when operating for an extended period time while increasing the concentration of injected hydrogen sulfide, the amount of sulfate was increased from 2 mg/L to 12.7 mg/L, and pH was rapidly reduced to 2.7.

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.