Digesters at water resource recovery facilities (WRRFs) operating at different temperatures within the mesophilic and thermophilic temperature range is a flexibilization concept to contribute to heat management. Four 25 L digesters were fed with sewage sludge from a municipal WRRF and were operated at 37, 43, 47 and 53 °C, respectively, to describe changes in the overall process performance and the microbiota. Specific methane yield and COD degradation rates were the highest at 47 °C, only being up to 7% higher compared with at 37 °C. The increase in pH and concentrations of NH₄-N and PO₄-P above 43 °C were statistically significant. The effect on the microbial community was strong, indicating both a constant specialization towards thermophilic organisms as well as a change from acetoclastic to hydrogenotrophic/methylotrophic methanogenesis. The influence of temperature on process-engineering and physicochemical aspects was rather small compared with the changes in the microbiota.

In this study, seven full‐scale anaerobic digesters, with or without co‐substrate regime, were analysed by physicochemical and molecular biological methods. A combination of robust community fingerprinting and Illumina MiSeq sequencing revealed a core bacterial community dominated by Chloroflexi, Firmicutes, Bacteroidetes and Proteobacteria, with variations in the profiles because of differences in the co‐substrate feeding regime. Despite these differences, physicochemical properties revealed a stable performance of all reactors, indicating a resilient bacterial microbiota in all full‐scale reactors. A rich bacterial core community ensured reactor functionality, whilst feeding regime and reactor type impacted the overall and the core bacterial diversity. Within the Archaea, Methanosaeta dominated in all reactors. Results indicated no relationship between archaeal community structure and the type of co‐substrate digested. Methanogens rely on the metabolic end products of bacterial activity and are thus less dependent on differences in the initial co‐substrate regime.

In recent years, there has been a veritable boost in next-generation sequencing (NGS) of gene amplicons in biological and medical studies. Huge amounts of data are produced and need to be analyzed adequately. Various online and offline analysis tools are available; however, most of them require extensive expertise in computer science or bioinformatics, and often a Linux-based operating system. Here, we introduce “CoMA–Comparative Microbiome Analysis” as a free and intuitive analysis pipeline for amplicon-sequencing data, compatible with any common operating system. Moreover, the tool offers various useful services including data pre-processing, quality checking, clustering to operational taxonomic units (OTUs), taxonomic assignment, data post-processing, data visualization, and statistical appraisal. The workflow results in highly esthetic and publication-ready graphics, as well as output files in standardized formats (e.g. tab-delimited OTU-table, BIOM, NEWICK tree) that can be used for more sophisticated analyses. The CoMA output was validated by a benchmark test, using three mock communities with different sample characteristics (primer set, amplicon length, diversity). The performance was compared with that of Mothur, QIIME and QIIME2-DADA2, popular packages for NGS data analysis. Furthermore, the functionality of CoMA is demonstrated on a practical example, investigating microbial communities from three different soils (grassland, forest, swamp). All tools performed well in the benchmark test and were able to reveal the majority of all genera in the mock communities. Also for the soil samples, the results of CoMA were congruent to those of the other pipelines, in particular when looking at the key microbial players.