Facultative-like anaerobic packed bed reactor treating low strength wastewater: microbial community and energy balance appraisements

This study explored the microbial community and the energy requirement of an anaerobic packed bed reactor (APBR) treating a low-strength synthetic wastewater (200 mg COD/L). The APBR was run with different hydraulic retention times (HRTs) and temperatures. Results show that the COD removal decreased from 89 to 46% when the HRTs and the temperature were both gradually reduced to 1 h and 20 degrees C. Meanwhile, the methane yield decreased from 0.386 to 0.232 g COD/g TCODconsumed with the decreasing temperature from 35 to 20 degrees C at 1-h HRT. This low methane production was associated with a low relative abundance of 0.575-0.628% for the archaea group in genus level. Genus Methanosaeta with 0.307-0.388% relative abundance represented 53-62% of the archaea group whereas facultative Trichococcus with 7.3-11.3% relative abundance was dominant in the microbial consortia. Candidatus Moduliflexus found was the second largest microbial population with 4.2-6.1% relative abundance. This facultative environment was observed in the APBR, resulting in 18-37% COD unbalanced. The energy appraisement resolved that the total electrical energy required for the APBR was consistent at 4.192 x 10(-3) kWh/m(3) at 20-35 degrees C to yield the net energy ratio of 5.97-15.29. The facultative-like APBR treated the low strength wastewater efficiently while the energy input was balanced by its self-produced methane energy. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Automated summary

This study investigated the microbial community and energy requirements of an anaerobic packed bed reactor treating low-strength synthetic wastewater under different HRTs and temperatures. The results showed that as the HRT and temperature decreased, COD removal and methane yield also decreased. The microbial community with low relative abundances of archaea and facultative bacteria played a significant role in the reactor's efficiency.