The performance of the new aerobic digestion system combined with inorganic sludge separation unit and sludge solubilization unit, CaviTec II, is evaluated. Anaerobic digester effluent sludge is used for feed sludge of CaviTec II system. By addition of CaviTec II, the amount of cake generated is reduced by 27%, and the soluble nitrogen is reduced by 92%.

In the general process of design for aerobic digestion, the design for field plant of which inflow pattern is continuous inflow is performed using the results from lab scale batch reactor. However, the recent researchers reported that the general designs were performed as over-estimated, Therefore, in this study, laboratory batch experiments were carried out at $20^{\circ}C$ and pH 7.5 on the aerobic digestion of waste activated sludge at different solid levels. This treatise could consider the negligence about effective digestion periods the usage of VSS as solid concentration, and the effect of initial solid concentration of solid degration rate coefficient($k_d$) as reasons of the overestimated design, and showed the scheme of how to design for aerobic digestion from batch experiment.

This research examined the possibility of the temperature maintenance of an anaerobic digestion reactor without external heating by the oxidation heat generated in an aerobic fermenter, considering the difficulties of anaerobic digestion because of the winter season in Korea. For the experiment, an anaerobic digestion chamber was installed inside, the device with aerobic fermentation installed outside was used, the anaerobic digestion chamber was covered, and the raw material was used in the perspective of handling livestock excretion and food waste. During 230 days of operation in total, normal operation was started after about 120 days, and during that operating time, the temperature change, degradation behavior of organisms, and digestion yield were analyzed; the results are shown below. In the situation excluding the aerobic reactor in the summer season, maintaining the temperature of the digestion chamber at 30°C was possible through heat storage within the house, but the temperature decreased to about 20°C because of the outside temperature in the winter season, and maintaining the temperature of the digestion chamber at 25°C was possible as long as the aerobic fermentation chamber maintained its temperature of more than 50°C. Regarding the results for the effects of the inside and outside temperature of the house on the aerobic reactor chamber temperature, a significant effect was not examined, and it was identified that the aerobic reactor temperature relied on the degree of aerobic microorganism vitalization. When using a hot-water system with solar heat, the possibility of usage as complementary energy in the unstable winter season was checked. Even in the winter season, maintaining the temperature of the anaerobic digestion chamber without external heating was possible, and even during the time of operation, although the temperature changed from 25°C to 38°C, methane gas was stably produced.