Anaerobic Treatment of Sewage Sludge Treated by Catalytic Wet Oxidation Process in Upflow Anaerobic Sludge Blanket Reactors

Abstract

To increase the efficiency of methane recovery in anaerobic treatment, sewage sludge was treated by catalytic wet oxidation process(CWOP).The CWOP is designed to treat sewage sludge with the aid of a newly developed catalyst. It is a treatment process, by which concentrated COD components and suspended solids in various kinds of sludge can be simultaneously oxidized and treated with great efficiency in a single step without dilution. After CWOP, this supernatant was treated by upflow anaerobic sludge blanket(UASB) for recovery of methane. This experiment was to evaluate the acclimation of UASB process to the supernatant of sewage sludge treated by CWOP. For the granule growth and accumulation, supernatant was introduced stepwise (25%, 33%, 50%, 100%). The supernatant was 7,200 mg-COD/L which contained 53% carbonic acids. The reactor was operated at a volumetric loading rate from 1.8 (kg·COD/m3·day) to 14.4 (kg·COD/m3·day) and overall HRT of less than 24 hrs throughout the experiment. In the conventional anaerobic biochemical process of methane gas recovery was limited to 50% of COD recovery. As a result of this study, the COD recovery to about 93% was obtained by the coebination of CWOP and UASB process. The following conditions were enough for pretreatment: temperature, 270°C; pressure, 86kg/m2; stoichiometric air ratio, 1.1; reaction time, 24 min. These results indicate that the CWOP-UASB process may be attractive as an alternative sewage sludge treatment.