The Study Of Sewage Sludge Treatment By Autothermal Thermophilic (Micro)aerobic Digestion Process

Shanghai Municipal Sewage Plants will be reconstructed due to a lack of sludge treatment facilities. Sludge digestion processes, which are characterized by small volume digesters, high removal efficiency and sanitation, are needed by small or medium-sized sewage plants that are distributed downtown and surrounded by residential area. However, neither anaerobic digestion process nor conventional Aerobic Digestion (CAD) processes can be adopted to apply in the plants. Anaerobic digestion needs large volume digester and produce odour and insanitation. CAD processes have disadvantage of relatively long retention time, not resistance to low temperature and not destruction pathogans. Autothermal Thermophilic Aerobic Digestion (ATAD) technology can be adapted to treat domestic sludge in small or medium-sized communities. ATAD can also achieve a thermophilic temperature (45-65 ℃) without an external heat, which have apparent technical benefits of high degradation rate, short detention time, small volume of one-sixth to one-half less than that of conventional aerobic and anaerobic digestion, resisting low temperature, and especially, efficient destruction pathogens to stabilize and pasteurize municipal sludge.There is no relative study about ATAD process in China, though, full-scale application experience is more than 20 years in Europe. To elude property right protection of present ATAD technology, a novel, self-developed, one-stage ATMD (Autothermal thermophilic Micro-aerobic Digestion) that equipped with sludge recirculation system, efficient air aeration equipment and foam control system was designed, and possessed with patent protection. A pilot-scale demonstration study was undertaken in Shanghai Municipal Sewage Plant. By the practice, one-stage ATMD can stabilize and pasteurize sludge at 10 days sludge detention time(SRT). By way of batch and semi-batch operation, optimal values of factors were obtained, and sludge qualities were further studied on the basis of optimal values, sludge reaction mechanism was also discussed.