Biofilm formation and granule properties in anaerobic digestion at high salinity

Abstract

For the anaerobic biological treatment of saline wastewater, Anaerobic Digestion (AD) is currently a possibility, even though elevated salt concentrations can be a major obstacle. Anaerobic consortia and especially methanogenic archaea are very sensitive to fluctuations in salinity. When working with Upflow Sludge Blanket Reactor (UASB) technology, in which the microorganisms are aggregated and retained in the system as a granular biofilm, high sodium concentration negatively affects aggregation and consequently process performances. In this research, we analysed the structure of the biofilm and granules formed during the anaerobic treatment of high salinity (at 10 and 20 g/L of sodium) synthetic wastewater at lab scale. The acclimated inoculum was able to accomplish high rates of organics removal at all the salinity levels tested. 16S rRNA gene clonal analysis and Fluorescence In Situ Hybridization (FISH) analyses identified the acetoclastic Methanosaeta harundinacea as the key player involved acetate degradation and microbial attachment/granulation. When additional calcium (1 g/L) was added to overcome the negative effect of sodium on microbial aggregation, during the biofilm formation process microbial attachment and acetate degradation decreased. The same result was observed on granules formation: while calcium had a positive effect on granules strength when added to UASB reactors, Methanosaeta filaments were not present and the degradation of the partially acidified substrate was negatively influenced. This research demonstrated the possibility to get granulation at high salinity, bringing to the forefront the importance of a selection towards Methanosaeta cells growing in filamentous form to obtain strong and healthy granules.

Assessment of multiple anaerobic co-digestions and related microbial community of molasses with rice alcohol wastewater

“…Methanosaetaceae, the methanogens can survive at both high and low concentrations of acetate [57,58]. In both the mono-digestion and co-digestion process, Methanobacteriaceae was found in all stages and ranged from 12.02-20.44%, which is in the line with the work of Gagliano et al [59] and Ziganshin et al [60]. Methanobacteriaceae is the primary user of formate and H2/CO2 substrates for methane formation.…”

Characterization of Core Microbiomes and Functional Profiles of Mesophilic Anaerobic Digesters Fed With Chlorella vulgaris Green Microalgae and Maize Silage

“…Genera Paenibacillus, Pseudomonas, Terrisporobacter, Actinomyces, Geofilum, Lachnoclostridium, Cryseobacterium, Oscillibacter, Acetivibrio, and Parabacteroides were found in lower abundances among core microbes (Nelson et al, 2011;Shida et al, 2012;Lee et al, 2013;Yan et al, 2013;Cho et al, 2015;Pap et al, 2015;Sun et al, 2016;Gagliano et al, 2017;Lemos et al, 2017;Nakajima et al, 2017;Neshat et al, 2017;Tian et al, 2017) (Supplementary Table 2).…”

Microbial Community Drivers in Anaerobic Granulation at High Salinity

“…Methanosaeta harundinacea cells were shown to significantly enhance granulation and performance of UASB reactors (Li et al, 2015). Our group demonstrated that M. harundinacea is a key-microorganism to obtain compact granules in UASB reactors at low and high salinity conditions, when using a salt-adapted, Methanosaeta-rich inoculum (Gagliano et al, 2017(Gagliano et al, , 2018Sudmalis et al, 2018).…”

“…As consequence, non-adapted granules disintegrate, causing biomass wash-out and deteriorating process performance (Rinzema et al, 1988;Vallero et al, 2003;Ismail et al, 2008). Still, utilization of salinity adapted biomass was successfully applied to overcome this issue and obtain strong aggregates/granules (Feijoo et al, 1995;Hierholtzer and Akunna, 2014;Gagliano et al, 2017;Sudmalis et al, 2018).…”