침지형 평막결합 연속회분식 반응기를 이용한 폐수처리

Abstract

The submerged membrane-coupled sequencing batch reactor (MSBR) is a promising technology for wastewater treatment in a small scale. A flat-sheet microfiltration membrane, made of PVC with a pore size of 0.4 ㎛, was submerged in this reactor. The effects of operation modes on filtration performance and its removal efficiency were investigated in flat-type membrane-coupled sequencing batch reactor (FMSBR). Three sets of operation modes during 133 days were conducted to identify their effects on the filtration performance and its removal efficiency. MLSS concentrations in the reactors increased during operating time, and then maintained a constant concentration after 80 days. As for the removal efficiency, there was no wide difference among three sets of operation modes. Average removal efficiencies of COD, SS, T-N, and T-P in permeation were more than 95%, 100%, 82%, and 95%, respectively, at all modes. But in the filtration performance, time cycle on non-aeration and aeration of 60/120 min/min was more effective than 120/240 min/min, and the operation mode of intermittent filtration was more effective than that of continuous filtration. When time cycle of non-aeration and aeration was set up 60/120 min/min, membrane filtration was able to be continued for 127 days without membrane cleaning, and was recovered after this cleaning. The effect of organic material loadings on nutrient removal characteristics were also investigated in FMSBR. In order to identify their effects on filtration performance and nutrient removal, three organic concentrations of 200 mg/L (Run-1), 400 mg/L (Run-2) and 800 mg/L (Run-3), respectively, were continuously carried out. MLSS concentration increased continuously at operating time and average rate of MLSS change increased as the increase oforganic material loading. Removal efficiency of COD decreased with the increase of loading. The removal efficiencies of T-N and T-P were increased with the increase of COD/N and COD/P. This result indicated that most of membrane filtration resistance was found to be caused by cake resistance formed at membrane surface. In the operation of FMSBR, the effects of filling step on the removal efficiency and its filtration performance were investigated. Two sets of operation modes were conducted during 82 days: (1) the filling step located in the beginning of aerobic step and (2) that in the beginning of anoxic step. There was no wide difference in the COD removal and filtration performance between two sets of operation modes. But in the removal efficiency of nutrients (total nitrogen and total phosphorous), the filling step located in beginning of anoxic step was found to be more effective than that of aerobic step. In this study, we studied on a hybrid reactor for the study of wastewater treatment. The hybrid reactor was another type of FMSBR with sponge type media submerged. Dosages of the media in the hybrid reactor were set of 5%, 10%, and 20% based on working volume of hybrid reactor. As a control system, FMSBR was also operated. The experimental results showed that MLSS and MLVSS concentrations for four different volume of sponge media increased continuously during the operation time. There was also no difference observed in the removal efficiencies of COD, T-N, and T-P irrespective of the dosages of the media. But TMP of the hybrid reactor increased slowly during the operation time, while that of FMSBR increased rapidly at the initial operation. This result was thought that the collisions between flat membrane and moving media gave friction forces which mitigated the cake layer on the surface of flat type membrane. Consequently, this study showed that filtration performance of the hybrid reactor was greatly enhanced compared with that of FMSBR. The hybrid reactor suggested in this study can be a good candidate for the wastewater treatment.