Characteristics of Volatile Fatty Acid and Oxidation Reduction Potential for Treating Municipal Wastewater in Modified EGSB

The traditional Expanded Granular Sludge Bed (EGSB) reactor was modified to treating municipal wastewater. The characteristics of Oxidation Reduction Potential (ORP) and Volatile Fatty Acid (VFA) concentration of effluent was studied to judge to the operation condition of anaerobic degradation process. The characteristics of ORP and VFA for treating municipal wastewater was studied in modified Expanded Granular Sludge Bed (EGSB). The result showed that the VFA concentrations of outlet were greater in higher temperature (>25°C) than that of in lower temperature (7~13°C) during system starting up, as 180 mgL^-1 and 120 mgL^-1 respectively. The alkalinity in the reactor was 400 mg·L^-1 during lower temperature period, and 600 mg·L^-1 in higher temperature period. During the running period, the VFA concentration decreased from 35.92 mg·L^-1 to 38 mg·L^-1 with the Hydraulic Retention Time (HRT) increasing from 0.5 h to 7.0 h. The Oxidation Reduction Potential (ORP) was obviously negative relative with the COD removal efficiency in the reactor during the running period. The range of change of ORP decreased from -410 MV to -520 MV in 9-months operation with the temperature increasing from 8°C to 30°C.