Pilot Study On Treatment Of Sauce Wastewater With Anaerobic Baffled Reactor At Ambient Temperatures

In recent years, Anaerobic Baffled Reactor (ABR) has become one of the hottest research topics in the field of anaerobic reactor with its simplified structure, advanced sludge retention ability and effective treatment.The research accomplishment by our group on the ABR has been applied on pilot studies of soy sauce wastewater treatment. The trial was started at low concentration and room temperature using the granular sludge as seed and actual wastewater as inoculated substrate. The influent COD ranged from 1000mg/l to 4000 mg/l. The COD removal rate was around 85%. The effluent VFA was maintained under 542mg/l. The pH values stabilized at about 7.0. After 40 days, the influent volumetric loading reached 3.1kgCOD / (m3·d), the effluent VFA was less than 600mg/l, the pH value was about 7.0, and COD removal rate was above 89%, which was a successful start-up. Therefore, the time used for starting-up the reactor was greatly reduced by inoculating anaerobic granular sludge into the ABR.The degradation characteristics of soy sauce wastewater, which includes the system degradation characteristics of organic matter and changes in VFA, ammonia, pH and color, were investigated during the continuous operation of the reactor. During the stable stage, the sodium hydroxide and bicarbonate were added to adjust the pH and alkalinity, respectively. The COD removal rate was above 87% after 30 days of continuous feeding. According to the test results, the COD degradation of the first cell is at about 70% of the overall system. Therefore, the stable operation of the first cell of ABR is very important when dealing with the refractory organic wastewater. Most part of the load is at the first cell so that it is important to optimize the conditions of the design and operation of ABR.The ABR reactor has effect on the color removal of soy sauce wastewater but not significant on the NH3-N removal. During the stable operation, the pH value and the effluent VFA fluctuated between 6.3 ~ 7.3 and 181 ~ 600mg/l, respectively. There were no organic acids accumulated in the reactor.During the experiment, there were significant changes in each cell. Inoculated sludge was black. The first cell was operated long-termly under the high load. As a result, there was variety of acid-producing bacteria and the sludge is slightly black in the first cell. The load is relatively low in the second and third cell, so there was no significant change with the color of the sludge, which was mainly black. Larger sludge granules were formed in each cell, which raised the granulation level. It is mainly related to the viscosity of liquid mixture and structural composition of granular sludge in cells. During the treatment of soy sauce wastewater, the color of the granular sludge was gradually changed from dark-gray to black. There was decrease in the particle size. However the settlement rate was increased, which indicated that the sludge became denser during the process.