Pilot-scale coagulation and sedimentation processes were operated to investigate the T-P (Total phosphorus) removal efficiency. A multiple regression model was also derived to predict the water quality improvement effect with river water characteristics. The inflow rates for the pilot-scale facility were 157–576 m3/day, and the coagulant doses were in the range of 13.7–58.5 mg/L (average 38.9 mg/L) for PAC (Poly alum chloride) and 16.5–62.1 mg/L (average 36.0 mg/L) for alum. The results found that the influent BOD (Biochemical oxygen demand) and T-P concentrations were 4.9 mg/L and 0.115 mg/L, and the removal efficiencies were 52.7% and 59.4%, respectively. T-P removal efficiencies on wet weather days were higher by 10% than dry weather days because influent solids influenced T-P's coagulation process. The pH of river water was 6.9–7.8, and the average pH was 7.3. Although the pH variation was not significant, the trend showed that the treatment efficiency of T-P and PO4-P removal increased. Thus, the pH range considered in this study seems to be appropriate for the coagulation process, which is essential for phosphorous removal. The T-P removal efficiencies were 19.6–93.3% (average 59.2%) for PAC and 16.4–98.5%(average 55.9%) for alum; thus, both coagulants showed similar results. Furthermore, the average coagulant doses were similar at 42.4 mg/L for PAC and 41.3 mg/L for alum. When the T-P concentration of the effluent was compared by the [Al]/[P] ratio, the phosphorus concentration of the treated water decreased with an increasing [Al]/[P] ratio, and the lowest T-P concentration range appeared at the [Al]/[P] ratio of 10–30. A seasonal multiple regression analysis equations were derived from the relationships between 10 independent and dependent variables (T-P concentration of effluent). This study could help lake water quality maintenance, reduce eutrophication, and improve direction settings for urban planning, especially plans related to developing waterfront cities.

최근 방류수 수질 강화에 따라 총인 처리시설의 설치와 응집제 사용량이 증가하고 있다. 본 연구는 유입하수에 포함된 응집제 성분(Al3+, Fe3+ 등)을 활용하여 PO43-와 응집시킴으로써 하수처리공정에 별도의 응집제 주입 없이 총인 농도를 0.2mg/L 이하로 제거할 수 있는 MBR 하수처리공정을 개발하는 것이다. 활성슬러지와 차아염소산나트륨으로 제조한 알칼리슬러지를 MBR 공법의 생물반응조에 주입하여 적정 pH를 유지시킴으로써 유입하수 중의 용존성 이온을 상호 응집시켜 고형화 하였고 분리막으로 고액 분리하여 하수처리수의 총인 농도를 0.2mg/L이하로 달성하였다. 이 연구를 통해 개발한 공법은 응집제 주입 없이 하수처리수의 총인 농도를 0.2mg/L이하로 제거하여 약품비용을 절감에 기여할 것으로 예상된다.

In this study, an operational data set was analysed by establishing a path model to figure out the actual cause-effect relationship of a wastewater treatment plant (WWTP); in particular, for the effluent concentrations of T-N and T-P. To develop the path models, data sets of operational records including effluent concentrations and operational factors were obtained from a field scale WWTP of 680,000 m3 of treatment capacity. The models showed that the relationship networks with the correlation coefficients between variables for objective expressions indicated the strength of each relationship. The suggested path models were verified according to whether the analyzation results matched known theories well, but sophisticated minute theoric relationships could not be cropped out distinctly. This indicates that only a few paths with strong theoric casual relationships were represented as measured data due to the high non-linearity of the mechanism of the removal process in a biological wastewater treatment.

This study aimed to evaluate changes in the TN and TP removal efficiencies, depending on whether or not a settling process is applied, in a sequencing batch reactor (SBR) process with a membrane bioreactor (MBR). Nutrient removal was considered in terms of developing an advanced water treatment system for ships in accordance with water quality standards set forth by 227(64). For these purposes, the TN and TP concentrations in the inflow and outflow water were measured to calculate the TN and TP removal efficiencies, depending on whether or not a settling process was used. Water discharged from a bathroom, which was constructed for the experiment, was used as the raw water. The experiment that included a settling process was conducted twice, and the operating conditions were: aeration for 90 min, settling for 30 min, agitation for 15 min, and settling for 15 min for one experiment; and aeration for 150 min, settling for 45 min, agitation for 15 min, and settling for 15 min in the other. Operating conditions for the experiment that did not include a settling process were: aeration for 180 min and agitation for 60 min. The concentration of the mixed liquor suspended solids (MLSS) in the reactor was 3,500 mg/L, while the aeration rate was 121 L/min and the water production rate was 1.5 L/min. For the two experiments where a settling process was applied, the average TN removal efficiencies were 44.39% and 41.05%, and the average TP removal efficiencies were 47.85% and 46.04%. For the experiment in which a settling process was not applied, the average TN removal efficiency was 65.51%, and the average TP removal efficiency was 52.51%. Although the final nutrient levels did not satisfy the water quality standards of MEPC 227(64), the TN and TP removal efficiencies were higher when a settling process was not applied.

The aim of this paper is to compare the characteristics of the T-P removal from synthesized municipal wastewater by electro-coagulation using cylindrical Al and Fe electrode as anode. For this purpose, a concentric circle type electrolysis reactor was used and the operating conditions for T-P removal from synthesized wastewater are as follows; potential 10 V, electrolyte 0.03% NaCl, initial T-P concentration 1.0 ~ 6.0 mg/L and flow rate 1.0 ~ 5.0 L/min. From the experimental results, T-P concentration of treated wastewater was decreased to less than 0.2 mg/L enough to discharge standard and Al electrode showed performance than Fe electrode for T-P removal by electro-coagulation. Optimal conditions for T-P removal to less than 0.15 mg/L which is 75% of discharge standard for large scale municipal wastewater plant (capacity higher than 500 m3/day) were obtained as follows; flow rate 2.503 L/min, and 2.337 L/min, HRT 1.059 min, 1.134 min, for Al and Fe electrode, respectively. Consumed mass of Al and Fe were of 3.76 times and 8.90 times respectively, were obtained to removed T-P at optimal conditions with potential 10 V, and 0.03% NaCl as electrolyte.

T-N and T-P in the filtrate from Sludge Treatment Process (STP) was returned to water treatment processing, because T-N and T-P are returned, it makes overload in Advanced Treatment Process. Removal efficiency of T-N and T-P are compared both at using polymer as simple method and at using PFS and polymer as complex method when coagulants was injected in Thickener. In simple method, removal efficiency of T-N and T-P were 95.68% and 99.29% for each. In complex method, removal efficiency of T-N and T-P were 98.07% and 99.90% for each. From the result, removal efficiency of complex method was highly better than simple method. According to increasing of removal efficiency, returned T-N and T-P loading to water treatment process was decreased (Reduced amount of T-N is 0.2309 kg/hr and TP is 0.0145 kg/hr). Also, the amount of a polymer used has been decreased to 80% by using PFS.