This study investigates the effect of the organic loading rate (OLR) increase from 1.0 to 3.5 g VS L(-1) day(-1) at constant hydraulic retention time (HRT) of 35 days on anaerobic reactors' performance and microbial diversity during mesophilic anaerobic digestion of ammonium-rich chicken wastes in the absence/presence of zeolite. The effects of anaerobic process parameters on microbial community structure and dynamics were evaluated using a 16S ribosomal RNA gene-based pyrosequencing approach. Maximum 12 % of the total ammonia nitrogen (TAN) was efficiently removed by zeolite in the fixed zeolite reactor (day 87). In addition, volatile fatty acids (VFA) in the fixed zeolite reactor accumulated in lower concentrations at high OLR of 3.2-3.5 g VS L(-1) day(-1). Microbial communities in the fixed zeolite reactor and reactor without zeolite were dominated by various members of Bacteroidales and Methanobacterium sp. at moderate TAN and VFA levels. The increase of the OLR accompanied by TAN and VFA accumulation and increase in pH led to the predominance of representatives of the family Erysipelotrichaceae and genera Clostridium and Methanosarcina. Methanosarcina sp. reached relative abundances of 94 and 57 % in the fixed zeolite reactor and reactor without zeolite at the end of the experimental period, respectively. In addition, the diminution of Synergistaceae and Crenarchaeota and increase in the abundance of Acholeplasmataceae in parallel with the increase of TAN, VFA, and pH values were observed.

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Anaerobic digestion is an important technology to receive energy from various types of biomass. In this work, the impact of granular activated carbon (GAC) on the mesophilic anaerobic co-digestion of sugar beet pulp and distillers grains was investigated. After a short period, anaerobic reactors began to produce biomethane and were ready for completion within 19–24 days. The addition of GAC to reactors (5–10 g L−1) significantly enhanced the methane production rate and consumption of produced volatile fatty acids. Thus, the maximum methane production rate increased by 13.7% in the presence of GAC (5 g L−1). Bacterial and archaeal community structure and dynamics were investigated, based on 16S rRNA genes analysis. The abundant classes of bacteria in GAC-free and GAC-containing reactors were Clostridia, Bacteroidia, Actinobacteria, and Synergistia. Methanogenic communities were mainly represented by the genera Methanosarcina, Methanoculleus, Methanothrix, and Methanomassiliicoccus in GAC-free and GAC-containing reactors. Our results indicate that the addition of granular activated carbon at appropriate dosages has a positive effect on anaerobic co-digestion of by-products of the processing of sugar beet and ethanol distillation process.

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The microbial community structures of two continuous stirred tank reactors digesting turkey manure with pine wood shavings as well as chicken and swine manure were investigated. The reactor fed with chicken/swine wastes displayed the highest organic acids concentration (up to 15.2 g/l) and ammonia concentration (up to 3.7 g/l ammonium nitrogen) and generated a higher biogas yield (up to 366 ml/g(VS)) compared with the reactor supplied with turkey wastes (1.5- 1.8 g/l of organic acids and 1.6-1.7 g/l of ammonium levels; biogas yield was up to 195 ml/g(VS)). The microbial community diversity was assessed using both sequencing and profiling terminal restriction fragment length polymorphisms of 16S rRNA genes. Additionally, methanogens were analyzed using methyl coenzyme M reductase alpha subunit (mcrA) genes. The bacterial community was dominated by members of unclassified Clostridiales with the prevalence of specific clostridial phylotypes in each reactor, indicating the effect of the substrate type on the community structure. Of the methanogenic archaea, methanogens of the genus Methanosarcina were found in high proportions in both reactors with specific methanosarcinas in each reactor, whereas the strict hydrogenotrophic methanogens of Methanoculleus sp. were found at significant levels only in the reactor fed with chicken/swine manure (based on the analyses of 16S rRNA gene). This suggests that among methanogenic archaea, Methanosarcina species which have different metabolic capabilities, including aceticlastic and hydrogenotrophic methanogenesis, were mainly involved in anaerobic digestion of turkey wastes.