Abstract
This study attempted high-rate thermophilic anaerobic digestion of sewage sludge by applying thermal pretreatment of waste activated sludge (170°C and 1hr) and trace metal addition (0.49 mg-Ni/L and 0.54 mg-Co/L). For this purpose, thermophilic anaerobic digesters were maintained at a short HRT of 10 days throughout this study. The thermal pretreatment not only increased VS and VSS destruction by 6% and 9%, respectively, but also improved dewaterability of digested sludge drastically. The trace metal addition showed negligible effect on the overall performance, except for the reduced VFA concentrations in the digested sludge with a statistical significance. DGT analyses implied that the majority of soluble Ni and a portion of soluble Co are present in a bioavailable form. Furthermore, the Co content in the influent sewage sludge was suspected to be insufficient nutritionally. Microbial analyses based on PCR-DGGE detected the archaea, Methanosarcina sp. and Methanosarcina thermophila, in the digested sludge.
