Evaluating digestion efficiency in full-scale anaerobic digesters by identifying active microbial populations through the lens of microbial activity

Anaerobic digestion is one of the best ways to re-use animal manure and agricultural residues, through the production of combustible biogas and digestate. However, the use of antibiotics for preventing and treating animal diseases and, consequently, their residual concentrations in manure, could introduce them into anaerobic digesters. If the digestate is applied as a soil fertilizer, antibiotic residues and/or their corresponding antibiotic resistance genes (ARGs) could reach soil ecosystems. This work investigated three common soil emerging contaminants, i.e., sulfamethoxazole (SMX), ciprofloxacin (CIP), enrofloxacin (ENR), their ARGs sul1, sul2, qnrS, qepA, aac-(6′)-Ib-cr and the mobile genetic element intI1, for one year in a full scale anaerobic plant. Six samplings were performed in line with the 45-day hydraulic retention time (HRT) of the anaerobic plant, by collecting input and output samples. The overall results show both antibiotics and ARGs decreased during the anaerobic digestion process. In particular, SMX was degraded by up to 100%, ENR up to 84% and CIP up to 92%, depending on the sampling time. In a similar way, all ARGs declined significantly (up to 80%) in the digestate samples. This work shows how anaerobic digestion can be a promising practice for lowering antibiotic residues and ARGs in soil.

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Microbiota of anaerobic digesters in a full-scale wastewater treatment plant

Archives of Environmental Protection ◽

10.1515/aep-2017-0033 ◽

2017 ◽

Vol 43 (3) ◽

pp. 53-60 ◽

Cited By ~ 20

Author(s):

Piotr Świątczak ◽

Agnieszka Cydzik-Kwiatkowska ◽

Paulina Rusanowska

Keyword(s):

Microbial Community ◽

Sewage Sludge ◽

Methane Production ◽

Treatment Plant ◽

Full Scale ◽

Successful Implementation ◽

Anaerobic Digesters ◽

Syntrophic Bacteria ◽

The Stability ◽

Microbial Groups

AbstractAnaerobic digestion is an important technology for the bio-based economy. The stability of the process is crucial for its successful implementation and depends on the structure and functional stability of the microbial community. In this study, the total microbial community was analyzed during mesophilic fermentation of sewage sludge in full-scale digesters.The digesters operated at 34–35°C, and a mixture of primary and excess sludge at a ratio of 2:1 was added to the digesters at 550 m3/d, for a sludge load of 0.054 m3/(m3·d). The amount and composition of biogas were determined. The microbial structure of the biomass from the digesters was investigated with use of next-generation sequencing.The percentage of methanogens in the biomass reached 21%, resulting in high quality biogas (over 61% methane content). The abundance of syntrophic bacteria was 4.47%, and stable methane production occurred at a Methanomicrobia to Synergistia ratio of 4.6:1.0. The two most numerous genera of methanogens (about 11% total) wereMethanosaetaandMethanolinea, indicating that, at the low substrate loading in the digester, the acetoclastic and hydrogenotrophic paths of methane production were equally important. The high abundance of the orderBacteroidetes, including the classCytophagia(11.6% of all sequences), indicated the high potential of the biomass for efficient degradation of lignocellulitic substances, and for degradation of protein and amino acids to acetate and ammonia.This study sheds light on the ecology of microbial groups that are involved in mesophilic fermentation in mature, stably-performing microbiota in full-scale reactors fed with sewage sludge under low substrate loading.

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