Psychrophilic anaerobic sequencing batch reactor with biofilm supported by solids from dairy manure

Abstract

<abstract> <bold>Abstract.</bold> Flushed manure handling systems are widely employed within large-scale dairy farms due to their reduced labor and mechanical failures. However, flushing systems produce a very dilute waste stream, which makes conventional dairy AD design inapplicable owing to the requirements of massive digester size and heating energy consumption. Microbial biomass retention is thus critical for ensuring the performance of an anaerobic digester at short hydraulic retention time (HRT). In applications of such dilute animal waste, the current biomass retention technologies using artificial biofilm support media are vulnerable to clogging caused by manure fiber. In this study, a new strategy, improving biomass retention with fiber material present within the dairy manure as biofilm carriers, was evaluated for treating flushed dairy manure in a psychrophilic anaerobic sequencing batch reactor (ASBR). A volumetric methane production rate of 0.24 L/L/d of and specific methane productivity of 0.19 L/gVS_loaded were achieved at a compromised HRT of 6 days with model simulation. It was proved that ASBR using manure fiber as support media not only improved methane production but also reduced the necessary HRT and temperature to achieve a similar treating efficiency compared with current technologies. The composition of the methanogenic community of the digester with the best methane production performance was revealed by sequence analysis of the partial 16S rRNA gene generated from constructed clone library. The ASBR at short HRTs was capable of establishing a Methanosarcina predominated methanogenic Archaea population, which led to a more stable and efficient anaerobic digestion process.