Research On Sludge Anaerobic Digestion

With the accelerated process of urbanization and environmental quality standards to improve, the sewage treatment rate has gradually increased and sludge production also increased dramatically. Sludge disposal methods include anaerobic digestion and aerobic digestion. But anaerobic digestion is considered cost-effective, one of the sludge treatment process. The conventional anaerobic digestion doesn’t only need a long time but also has a low rate of gas production. The processing capacity and efficiency of the conventional anaerobic digestion is not ideal.The sludge effect the rate of anaerobic digestion. With the development of municipal wastewater treatment ABR, The treatment effect is not only good but also produced a small amount of sludge, the sludge digestion has attracted people’s attention.In this paper, we carried out comparative experiments. One of the sludge is ABR Chinese reactor anaerobic sludge, the other is municipal treatment plants of aerobic sludge.We study and analyze the effectiveness of two kinds of anaerobic digestion for the anaerobic digestion process in engineering applications.We control the temperature of35℃. We carried out comparative experiment in the sludge dosage rate of2%,5%,8%,10%. We determined pH, VFA,TCOD, VSS and Gas production in120days. The result is that:The anaerobic digestion is the best at the sludge dosage rate of5%, two kinds of sludge degradation rate has a largest gap.We carried out comparative experiment in the sludge dosage rate of5%. After two kinds of sludge in the temperature (35℃) anaerobic digestion results showed that:Anaerobic sludge TCOD and VSS degradation rate were63%and62%, Aerobic sludge TCOD and VSS degradation rate were45%and43%, Anaerobic sludge VSS/SS is0.64, Aerobic sludge VSS/SS is0.53, The average gas production of anaerobic sludge is1.84L/d, The average gas production of aerobic sludge is1.30L/d, Anaerobic sludge moisture content becomes91.26%from97.67%, The volume of sludge is the original volume of22.8～32.0%,Aerobic sludge moisture content becomes94.75%from98.41%, The volume of sludge is the original volume of27.7～36.8%.But the SVI becomes bad after anaerobic digestion. The SVI of anaerobic sludge becomes90.6%from85.4%. The SVI of aerobic sludge becomes92.2%from80.8%.At the beginning of reaction, Because of Acid-producing bacteria decompose organic acid, the pH of system is higher with the decreasing of VFA. Anaerobic sludge reactor pH as low as6.72, the concentration of VFA is523mg/L. Aerobic sludge reactor pH as low as6.69, the concentration of VFA is556mg/L. As the reaction proceeded, In the role of methanogenics bacteria, The VFA convert to methane. The pH value with the decrease of VFA concentration increased and finally stabilized. The pH of two systems is stable between6.8to7.1. The VFA of anaerobic sludge digestion is stable at433mg/L. The VFA of aerobic sludge digestion is stable at474mg/L. There is a difference of43mg/L. The ORP of anaerobic sludge digestion is stable between-215mV to-244mV. The ORP of aerobic sludge digestion is stable between-212mV to-244mV. There is no more difference at the ORP.