High rate manure supernatant digestion

Abstract

The study shows that high rate anaerobic digestion may be an efficient way to obtain sustainable energy recovery from slurries such as pig manure. High process capacity and robustness to 5% daily load increases are observed in the 370 mL sludge bed AD reactors investigated. The supernatant from partly settled, stored pig manure was fed at rates giving hydraulic retention times, HRT, gradually decreased from 42 to 1.7 h imposing a maximum organic load of 400 g COD L(-1) reactor d(-1). The reactors reached a biogas production rate of 97 g COD L(-1) reactor d(-1) at the highest load at which process stress signs were apparent. The yield was ∼0.47 g COD methane g(-1) CODT feed at HRT above 17 h, gradually decreasing to 0.24 at the lowest HRT (0.166 NL CH4 g(-1) CODT feed decreasing to 0.086). Reactor pH was innately stable at 8.0 ± 0.1 at all HRTs with alkalinity between 9 and 11 g L(-1). The first stress symptom occurred as reduced methane yield when HRT dropped below 17 h. When HRT dropped below 4 h the propionate removal stopped. The yield from acetate removal was constant at 0.17 g COD acetate removed per g CODT substrate. This robust methanogenesis implies that pig manure supernatant, and probably other similar slurries, can be digested for methane production in compact and effective sludge bed reactors. Denaturing gradient gel electrophoresis (DGGE) analysis indicated a relatively fast adaptation of the microbial communities to manure and implies that non-adapted granular sludge can be used to start such sludge bed bioreactors.

Direct Lysis Glass Milk Method of Genomic Dna Extraction Reveals Greater Archaeal Diversity in Anaerobic Biodigester Slurry as Assessed Through Denaturing Gradient Gel Electrophoresis

“…In order to reveal the metagenomic attributes of the extracted DNA, nested PCR was performed on amplicons obtained with universal 16S primers. Many studies have employed DGGE profiles of the V3 regions in order to reflect the dominant community structure and to analyse the structural variation between different systems or the dynamics of the same system (Yu et al, 2008;Liu et al, 2009;Bergland et al, 2015). In the current study, the primers for V3 hyper variable regions of 16S rRNA gene generated the band of ~176 bp in agarose gel electrophoresis.…”

“…It could also be useful in tracing the variation of dominant microbial organism in a biogas digester. PCR/DGGE strategies are in vogue for the purpose of characterization of the microbial communities, and evaluation of the time required for adaptation of the granular inoculum to the conditions in the anaerobic reactors fed with manure (Bergland et al, 2015).…”

Microbial community dynamics and biogas production from manure fractions in sludge bed anaerobic digestion

“…Pig manure handling is described in Bergland et al . () while the influent properties are in Table . Both manure slurries were stored at 4°C until use.…”

“…The first three samples from the P reactors have been subject to microbial analyses previously (Bergland et al . ), but are included here for continuance. Samples of both influents were taken on day 35, 68 and 96.…”

Modelling Anaerobic Digestion during Temperature and Load Variations

“…Substrate and effluent samples were collected 1-2 times a week. Total chemical oxygen demand (COD T ), soluble COD (COD S ), total solids (TS), volatile solids (VS), total suspended solids (TSS), volatile suspended solids (VSS), pH, alkalinity, NH 4 + -N and VFA's (acetate, propionate, butyrate, iso-butyrate, valerate, iso-valerate) were analyzed as described in Bergland et al [8].…”