Anaerobic-Aerobic Treatment of Municipal Wastewaters with Full-Scale Upflow Anaerobic Sludge Blanket and Attached Biofilm Reactors

Abstract

The results of pilot experiments on municipal wastewater treatment using advanced processes are described. The most important aims of this research were to achieve reductions in energy consumption, environmental impact, quantity of stabilized sludge produced, and area necessary for plant construction. The pilot plant, which was constructed in the environs of the Senigallia (AN, Italy) municipal wastewater treatment plant, had a capacity of 500 to 2500 population equivalents (p.e.). In the most attractive system, municipal wastewaters with a low organic concentration were first treated in an upflow anaerobic sludge blanket (UASB) bioreactor with a capacity of 336 m3. Part of the effluent from this process was then conveyed to an anoxic biological fluidized bed (with a volume of 8 m3 filled with 3 m3 of quartzite sand) for pre-denitrification, and then to an aerobic fixed bed (with random plastic media and a volume of 8m3) for nitrification. It was also possible to treat the municipal wastewaters using the anaerobic fluidized bed directly, after microscreening or primary sedimentation. The research undertaken was intended to verify the reliability of these processes at ambient temperatures and with variable wastewater concentrations. The preliminary results obtained for COD, BOD, and N removal from municipal wastewaters indicate that this system is quite an attractive treatment alternative, mainly due to its low sludge production and energy consumption. These results will enable accurate design criteria to be identified for the construction of more economic treatment plants on a larger scale.