Impact of anaerobic digestion and centrifugation/decanting processes in bacterial communities fractions

Abstract

Sewage sludge can be treated by anaerobic processes that frequently are followed by physical separation processes. In this work, a high-throughput sequencing technology, based on variation in the bacterial 16S rRNA gene, has been used to characterise the bacterial populations present in samples taken from different points of an industrial anaerobic digestion process fed with sewage sludge. Relative abundances of phyla and classes throughout the biological process and the subsequent separation steps were determined. Results revealed that the Bacteroidetes, Firmicutes and Proteobacteria phyla were the most representative. However, significant changes in relative abundance were detected along treatments, showing the influence of operational parameters on the distribution of microorganisms throughout the process. After anaerobic digestion, phylum Firmicutes doubled its relative abundance, which seems to indicate that the anaerobic conditions and the nutrients favoured its growth, in contrast to other phyla that almost disappeared. After centrifugation, Proteobacteria went preferentially to the solid phase, in contrast to Firmicutes which was the dominant phylum in the liquid phase. After decanting the liquid phase during 45 h, an important growth of Proteobacteria, Spirochaetes and Tenericutes was detected. At class level, only significantly changes were observed for Proteobacteria classes being α-proteobacteria dominant in the digestate, while γ-proteobacteria was the majority since this point to the final steps. To know the changes on the kind and abundance of microbial populations throughout the anaerobic and separation processes is very important to understand how the facilities design and operation conditions can influence over the efficiencies of next biological treatments.

Relative Weight of Organic Waste Origin on Compost and Digestate 16S rRNA Gene Bacterial Profilings and Related Functional Inferences

“…The urban samples (treated or not) had significantly more micropollutants including 14 TEs (Ag, Al, As, Cd, Ce, Co, Cr, Cu, Ga, Mo, Ni, P, Pb, and Ti), 4-nonylphenol, and 2 PAHs (phenanthrene and anthracene) than the agricultural and mixed (agricultural/urban; termed "central" in the text) samples. The 16S rRNA gene microbial community structures of the investigated OW urban samples were in agreement with previous studies (Juretschko et al, 2002;Wong et al, 2005;Hu et al, 2012;Díaz et al, 2018). Inferred 16S rRNA gene taxonomic allocations were predominantly among the Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes, and Nitrospirae phyla.…”

“…Both categories of digestates (urban and central/agricultural categories) were impacted by selective environmental changes, which led to a decrease in the relative abundance of Proteobacteria but an enrichment in Firmicutes (which nearly doubled in relative abundance). Firmicutes had been reported by several authors as one of the most abundant phyla in AD processes of activated sludge (Hu et al, 2012;Zhang et al, 2012;Abendroth et al, 2015;Díaz et al, 2018). Sundberg et al (2013) also found that Firmicutes were the most prevalent in samples taken from reactors fed with various combinations of wastes (from slaughterhouses, restaurants, households, etc.).…”

Metagenomic Analysis of Bacterial Communities from a Nitrification–Denitrification Treatment of Landfill Leachates

“…Microorganisms within this phylum have been described as important bacteria for the degradation of high‐molecular‐weight organic matter to acetic and propionic acid 20a . Their presence has been reported in anaerobic digestion processes fed with vegetal biomass, sludge, or mixed organic residues . Within Bacteroidetes phylum, Bacteroidia class was the most abundant representing around 70% of the phylum.…”

“…The restriction criteria applied was as follows: 1) read length filter: 150 bp, 2) minimum alignment coverage: 90%, 3) read abundance filter: 10, 4) genus cut off: 97%, and 5) species cut off: 99%. These criteria were selected according to previous works about microbial identification that used databases employed in this study …”

The influence of microbial community dynamics on anaerobic digestion efficiency and stability: A Review

“…Those four biochemical functions ( Fig. 2; Heeg et al 2014;Diaz et al 2018) are (i) hydrolysis of complex polymers into simple soluble products, (ii) acidogenesis (fermentation of simple soluble products into short-chain fatty acids), (iii) acetogenesis (anaerobic oxidation of short-chain fatty acids/volatile fatty acids (VFAs) into acetates and hydrogen), and (iv) methanogenesis (methane production from acetate and hydrogen by methylotrophic/acetoclastic and hydrogenotrophic methanogens).…”