High rate anaerobic digestion of primary and secondary sludge using the static granular bed reactor (SGBR)

摘要

The aim of this research was to demonstrate the feasibility of the static granular bed reactor (SGBR) as a replacement for the conventional mixed and heated anaerobic digester typically operating at municipal wastewater treatment plants (WWTP). The static granular bed reactor (SGBR) is a high rate anaerobic granular reactor. The SGBR operates at a short hydraulic retention time (HRT) (i.e 1 to 2 d) while maintaining a long solids retention time (SRT). Conversely to conventional digesters the SGBR separates the SRT from the HRT, reducing energy and volume requirements. The SGBR is downflow reactor with a dense bed of granules that entraps particles which helps to facilitate hydrolysis. Anaerobic treatment of primary and secondary municipal sludge was studied with a laboratory and pilot-scale SGBR at organic loading rates (OLR) from 2.8 ± 0.9 to 5.5 ± 1.7 g COD/L·d and 3.3 ± 2.0 g COD/L·d, respectively. The results of this research demonstrated the SGBR system\u27s potential to be a practical and competitive alternative to conventional anaerobic digestion of wastewater sludges. The laboratory (76 ± 4%) and pilot-scale (71 ± 0.4%) SGBR produced a biogas with a higher methane content than the conventional anaerobic digester tested (59 ± 2.8%). Effluent VFA concentrations remained below 40 mg/L as HAc, indicating the potential to reduce process instability due to the buildup of intermediates. The low VFA concentrations of the SGBR\u27s effluent also reduces odors compared to the liquid streams of conventional anaerobic digesters. The SGBR produced an effluent with low organic matter; average TSS and COD removal efficiencies remained above 90%.