Performance Improvement and Characteristics of Pumyang Sequencing Batch Reactor for Winter Season

When sequencing batch reactors (SBR) are used as small-scale sewage treatment plants, operational challenges arise from influent fluctuation and the inflow of unknown water due to the aging of sewage pipes. In particular, there are several operational problems due to the decrease in water temperature in winter. In this study, the operational performance of the Pumyang SBR (PSBR), a modified SBR with influent fluctuation and temperature, was analyzed. The reaction cycle of PSBR, with a hydraulic retention time (HRT) of 6 h, consists of filling (30-40 min), anaerobic conditions (60-90 min), aerobic conditions (90-120 min), settling (90-120 min), sludge transfer (5-10 min), and drawing (20-30 min). As a result, the concentrations of total organic carbon (TOC) and suspended solids in effluent water significantly changed depending on the temperature, with TOC being particularly affected. In winter, total phosphorus was reliably removed at influent sewage temperatures of <11℃, although treatment efficiency for total nitrogen tended to decrease. During the pilot plant operation, the food-to-microorganism (F/M) ratio ranged from 0.01 to 0.07 kg BOD/kg MLSS, corresponding to a mixed liquor suspended solids (MLSS) range of 1,550-2,960 mg/L. These findings indicate that the PSBR exhibited higher microbial density and faster settling than conventional activated sludge reactors. The results of this study will serve as fundamental data for the operation of small-scale sewage treatment facilities during winter.