Bioenergy Production and Slaughterhouse Wastewater Treatment in a Column-Type Anaerobic Sequencing Batch Reactor without Any External Mixer or Gas or Liquid Recirculation

Abstract

The performance of a column-type anaerobic sequencing batch reactor (ASBR) with a high height-to-diameter (H/D) ratio of 10 was evaluated while treating slaughterhouse wastewater. The reactor was operated without any external mixers, gas recirculation, or liquid recirculation. The chemical oxygen demand (COD) removal efficiency was about 70%–75% at different hydraulic retention times (HRTs) (48, 32, 24, and 12 h). Biogas production was stable at 4.5–8 L/day biogas, comprising about 60%–70% methane between 2 and 5.2 kg COD/m3·day. A high H/D ratio promoted good retention of denser sludge, and increased the production of biogas. The novel bioreactor without any external mixing and biogas/liquid recirculation is a promising technique, which can save considerable energy compared with conventional bioreactors if the biogas generated is maintained properly inside the ASBR. Additionally, microbial analysis targeting the 16S ribosomal RNA (16S rRNA) gene indicated the dominance of methanogens, which comprised Methanosaetaceae (23.07%), Methanobacteriaceae (2.05%), Methanomicrobiaceae (1.85%), Methanoregulaceae (0.82%), Methanocorpusculaceae (0.64%), and Methanospirillaceae (0.42%).