To investigate the effects of ozone pretreatment of waste activated sludge and the amount of additional municipal garbage （MG） on anaerobic co-digestion of sewage sludge and MG, we conducted continuous experiments with additional MG inputs of 10% and 15% by weight. The results of steady-state operation showed that biogas production increased significantly with the input of MG compared to the sewage sludge-alone system. The estimated net biogas production from MG was 898 NmL/g-VS or higher under all conditions, and was significantly higher in the ozone-treated system than in the untreated system at 15% MG input. Analysis of the microbial flora in the digested sludge showed that the change of flora was greater in the ozone-treated system, while the effect of MG input was small. Furthermore, based on the experimental results, the energy consumption and recovery during the running of a full-scale co-digestion system were calculated under a biogas power generation scenario. As a result, the net energy recovery was estimated to be higher with a 15% MG input than with a 10% input, and also higher when ozone pretreatment was applied.

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Stainless steel is used in sewage environments due to its various benefits. Corrosive microorganisms present in influent sewage and treated water affect material corrosion due to their reducing and oxidizing properties. Analysis of corrosive microorganisms and their effects on the corrosion resistance of stainless steels is important for the maintenance and management of facilities. Electrochemical measurements were carried out for evaluation the corrosion resistance of stainless steel in sewage treatment environments. The spontaneous potential of the stainless steel in front of the reaction tank gradually became less noble after the start of the measurement, and remained at a potential of -0.4 to -0.5 V vs. SSE. It is considered that the spontaneous potential of the stainless steel in the front of the reaction tank became less noble due to the action of anaerobic sulfate-reducing bacteria. The spontaneous potential of the stainless steel in the final sedimentation tank gradually became noble after the measurement started, reaching about 0.6V vs SSE in 6 months. After that, the spontaneous potential gradually became less noble, reaching 0.0V about a year and a half after the start of measurements. The spontaneous potential in the final sedimentation tank tended to be correlated with the dissolved oxygen concentration.

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