Biological Methanation in an Anaerobic Biofilm Reactor Raw sequence reads

iofilm reactors, so-called trickling bed reactors, offer a relatively simple, energy-efficient, and reliable technique for biogas upgrading via ex-situ methanation. A mesophilic lab-scale biofilm reactor was operated continuously for nine months to upgrade biogas from anaerobic sewage sludge digestion to a methane content >98%. To supply essential trace elements to the biomass, a stock solution was fed to the trickling liquid. Besides standard parameters and gas quality, concentrations of Na, K, Ca, Mg, Ni, and Fe were measured in the liquid and the biofilm using ICP-OES (inductively coupled plasma optical emission spectrometry) to examine the biofilms load-dependent uptake rate and to calculate quantities required for a stable operation. Additionally, microbial community dynamics were monitored by amplicon sequencing (16S rRNA gene). It was found that all investigated trace elements are taken up by biomass. Some are absorbed depending on the load, others independently of it. For example, a biomass-specific uptake of 0.13 mgg-1d-1 for Ni up to 50 mgg-1d-1 for Mg was found. Sequencing was performed at the Joint Microbiome Facility of the Medical University of Vienna and the University of Vienna under the project ID JMF-2212-06.