Air‐side ammonia stripping coupled to anaerobic digestion indirectly impacts anaerobic microbiome

Abstract

Summary Air‐side stripping without a prior solid–liquid phase separation step is a feasible and promising process to control ammonia concentration in thermophilic digesters. During the process, part of the anaerobic biomass is exposed to high temperature, high pH and aerobic conditions. However, there are no studies assessing the effects of those harsh conditions on the microbial communities of thermophilic digesters. To fill this knowledge gap, the microbiomes of two thermophilic digesters (55°C), fed with a mixture of pig manure and nitrogen‐rich co‐substrates, were investigated under different organic loading rates (OLR: 1.1–5.2 g COD l−1 day−1), ammonia concentrations (0.2–1.5 g free ammonia nitrogen l−1) and stripping frequencies (3–5 times per week). The bacterial communities were dominated by Firmicutes and Bacteroidetes phyla, while the predominant methanogens were Methanosarcina sp archaea. Increasing co‐substrate fraction, OLR and free ammonia nitrogen (FAN) favoured the presence of genera Ruminiclostridium, Clostridium and Tepidimicrobium and of hydrogenotrophic methanogens, mainly Methanoculleus archaea. The data indicated that the use of air‐side stripping did not adversely affect thermophilic microbial communities, but indirectly modulated them by controlling FAN concentrations in the digester. These results demonstrate the viability at microbial community level of air side‐stream stripping process as an adequate technology for the ammonia control during anaerobic co‐digestion of nitrogen‐rich substrates.

Similar Methanogenic Shift but Divergent Syntrophic Partners in Anaerobic Digesters Exposed to Direct versus Successive Ammonium Additions

“…Regarding bacteria, the highest NH 4 + conditions corresponded to the highest diversity of overabundant taxa. Among them, Tepidimicrobium enrichment in experiment 1 was consistent with previous studies reporting its prevalence (also in association with Methanoculleus ) in continuous AD of nitrogen-rich substrates up to 6.5 g TAN liter −1 ( 67 , 77 ) and in batch assays at extreme ammonia concentration above 25 g liter −1 ( 50 ). However, depending on the operating conditions, Tepidimicrobium can also be inhibited at high TAN, as observed in high solid digester at 5 to 6 g N-NH 4 + liter −1 ( 52 ).…”

“…The main SAO overexpressed at the highest ammonium level was affiliated with Syntrophaceticus . Known for its ammonia tolerance, Syntrophaceticus has been isolated from AD operating at 6.4 g N-NH 4 + liter −1 ( 79 ) and detected in ammonia-stripping AD ( 77 ). The amino acid degrader Gelria , known as syntrophic glutamate oxidizer ( 80 ), was also overabundant at high TAN in experiment 1, albeit in lower proportion.…”

Simultaneous Stripping of Ammonia from Leachate: Experimental Insights and Key Microbial Players

“…This technological solution is considered, e.g., in digesters processing bio-waste containing nitrogen-rich co-substrates. Fernandez-Gonzalez et al [61] proposed to pair thermophilic reactors with an air-side stripping column operated 3 h, 3 to 5 times a week, and treating 21% of the reactor volume in each batch, at 65 • C and without a pH control. In these conditions, the bacteria community, assessed by 16S rRNA gene sequencing analysis, was mainly composed of Firmicutes, which on average represented 80.2% of biomass, followed by Bacteroidetes (8.6%).…”

A critical review of ammonia recovery from anaerobic digestate of organic wastes via stripping

“…Serna-Maza et al [87] reported that introduction of side-stream stripping led to a decrease in TAN concentration (5 gN/kg to 3 gN/kg). In studies by Pedizzi et al [14] and Fernandez-Gonzalez et al [88], a decrease in TAN concentration from 2.5 to 1.1 g N/L in the digester and by a factor of 1/3, respectively, was observed upon re-circulation of stripped digestate. Inspite of the decreasing ammonia concentration in the stripping digesters, no significant change in methane yields was reported.…”

“…Several studies have reported a decrease in ammonia concentration in the digester when side-stream stripping was implemented [14], [87], [88], [89]. Serna-Maza et al [87] reported that introduction of side-stream stripping led to a decrease in TAN concentration (5 gN/kg to 3 gN/kg).…”