A high‐rate anaerobic biofilm reactor for biomethane recovery from source‐separated blackwater at ambient temperature

Abstract

Anaerobic bioreactors for source-separated blackwater are mostly operated at low organic loading rates (OLRs) due to low biodegradability and the potential of ammonia inhibition. In this study, an anaerobic biofilm reactor having conductive carbon fibers as the media was investigated for the high-rate treatment of blackwater collected from vacuum toilets. The bioreactor was operated at different OLRs ranged from 0.77 to 3.01 g COD/L-d in four stages for a total operating period of ~ 250 days. With the increase of OLRs, the specific methane production rate increased from 105.3 to 304.6 ml/L-d with high methane content in biogas (75.5%-83%). The maximum methane yield was achieved at hydraulic retention time (HRT) of 15 days. Highest organics and suspended solids removal (80%-83%) were achieved at 20-days HRT, while increased OLRs resulted in diminished removal efficiencies. The state variables, including pH, total ammonia nitrogen, short-chain volatile fatty acids, and soluble chemical oxygen demand, indicated the system had a great capability to withstand the high OLRs. Microbial community analysis revealed that the high performance might be attributed to direct interspecies electron transfer (DIET) facilitated by potentially electroactive bacteria (e.g., Syntrophomonas, Clostridium) and electrotrophic archaea (e.g., Methanosaeta and Methanosarcina species) enriched on the carbon fibers. © 2020 Water Environment Federation • Practitioner points • An anaerobic biofilm reactor was investigated for biomethane recovery from sourceseparated blackwater. • Conductive carbon fibers were utilized as the media to stimulate enrichment of potentially electroactive methanogenic communities. • The bioreactor was operated at ambient temperature for over 250 days. • High methane production rate and high-quality biogas were achieved at OLRs ranged from 0.77 to 3.01 g COD/L-d. • Microbial community analysis suggested direct interspecies electron transfer (DIET) between specific electroactive bacteria and electrotrophic archaea.

Coupling Microbial Electrolysis Cell and Activated Carbon Biofilter for Source-Separated Greywater Treatment

“…For instance, a recent study [17] reported a granular activated carbon (GAC) biofilter that could remove 94% chemical oxygen demand (COD) from greywater for a hydraulic retention time (HRT) of 2.4 h. Interestingly, energy recovery potential from greywater with anaerobic biotechnologies has been rarely investigated. Anaerobic bioprocess, such as anaerobic digestion, is usually known to be more effective for high-strength wastewater [18][19][20]. However, compared to anaerobic digestion, microbial communities in emerging microbial electrochemical systems, such as microbial fuel cells (MFCs), microbial electrolysis cells (MECs), can provide effective removal of organics from dilute wastewater, including domestic sewage [21][22][23][24].…”