Anaerobic Digestion of Synthetic Municipal Wastewater (MWW) in a Periodic Anaerobic Baffled Reactor (PABR): Assessment of COD Removal and Biogas Production

The benchmark approach for municipal wastewater treatment is based on biological oxidation. Due to high energy consumption, alternative treatment schemes are proposed, among which anaerobic digestion is the most promising. In this work, the direct anaerobic digestion of municipal wastewater in a high-rate system is examined. The reactor utilized for the study is the periodic anaerobic baffled reactor (PABR). Two distinct experimental cycles were conducted, during which the operational parameters of the PABR were consecutively modified: in the first cycle, six phases were conducted where the hydraulic retention time (HRT) varied from 10 to 1 days, the period T between 2.5 days and 0.25, while the OLR remained constant at values near 1.0 gsCOD/L/d. During the second cycle, four distinct phases were conducted with no switching imposed. The HRT varied from 4 to 1 d. The last experimental phase of both cycles was the most significant, due to feedstock resemblance to raw wastewater. The biogas and the biomethane production rates reached 66.8 L/d and 41.1 L/d, respectively, while the COD reduction rate reached 73.7%. Conclusively, the PABR is a high-rate AD system, capable of treating MWW under extreme operational conditions.