A total of 10,977 individual sewage treatment facilities(ISTFs) have been installed and operated on Jeju island as of 2022. The number of ISTFs has increased rapidly in the hillside area, where the elevation is above 200 m and is recognized as a major area for groundwater recharge. A total of 80 ISTFs were selected for this study, with a particular focus on their management status and effluent water quality. This was carried out in two areas, Aewol-eup and Jocheon-eup, which are known to have the highest density of ISTFs in Jeju island. Consequently, 23.9% of ISTFs failed to remove sludge regularly, and 41.3% of ISTFs did not run the blower. The effluent water quality revealed that violating percentage of the legal standards for BOD, SS, T-N, and T-P were 75.0%, 62.5%, 100%, and 86%, respectively. To assess the efficiency of effluent quality by management, an independent t-test and ANOVA were conducted. The BOD and TOC differed significantly according to the building usage. Therefore, it can be concluded that the effluent from ISTFs should be managed according to the building usage. Furthermore, no distinction was observed in contamination components due to blower operation, with the exception of DO. However, the mean value of the NH4 +-N/T-N ratio was found to decrease with DO, indicating that blower operation may potentially reduce the contamination burden of ammonium in groundwater.

This study was carried out to investigate the performance of individual sewage treatment facilities with MBR(membrane bioreactor). After ratio of influent distribution of aerobic reactor to anoxic reactor from 4 : 6 to 7 : 3, the effluent quality is improved 5.3 mg/L as BOD, 3.8 mg/L as SS, 5.6 mg/L as T-N, and 1.6 mg/L as T-P, respectively. The removal efficiency rate of effluent increased upto 98% as BOD, 99% as SS 94%, as T-N as 93% and T-P, respectively. To maintain SS concentration of the effluent less than 1 mg/L, the washing and differential pressure of membrane management were required, the wasted activated sludge periodically discard to the sludge storage tank in order to meet standard criteria. The capacity of this individual facilities was overestimated, when low loading occur, an alternative is considered