Integrated Rotary Drum and Anaerobic Phased Solids Digester System for Biogas Production from Municipal Solid Wastes

Abstract

This research was conducted to develop an integrated rotary drum reactor (RDR)-Anaerobic Phased Solids (APS) Digester system for the treatment of municipal solid waste (MSW) to produce biogas energy and achieve waste degradation. The RDR was used to provide pretreatment and separation of the organics from MSW and then the organics were digested in the APS-Digester system for biogas production. The solid retention time in the RDR was 3 d. The organics generated from the RDR contained 50% total solids (TS) and 36% volatile solids (VS) on a wet basis. The APS-Digester system is a two-phase, high-solids anaerobic digestion system which consists of four sequentially loaded batch hydrolysis reactors and one continuous biogasification reactor. The APS-Digester system was started at an organic loading rate (OLR) of 3.1 gVS L-1 d-1 and operated at three higher OLRs of 4.6, 7.7 and 9.2 gVS L-1 d-1. At the OLR of 9.2 gVS L-1 d-1 the systems biogas production rate was 3.5 L L-1 d-1 and the biogas and methane yields were 0.38 and 0.19 L gVS-1, respectively. Anaerobic digestion resulted in 38% TS reduction and 53% VS reduction in the organic solids. The changes of pH and volatile fatty acids (VFA) in all the reactors were measured. It was found that the total VFA concentration reached a peak value of 15000 mg L-1 as acetic acid in the first three days of batch digestion and later decreased to about 500 mg L-1. The APS-Digester system remained stable at each OLRs for over 100 d with a steady pH of 7.8 throughout.