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Chemical Factors
Published in Michael J. Kennish, Ecology of Estuaries Physical and Chemical Aspects, 2019
Ammonium (NH+4) is the predominant inorganic nitrogen species in estuarine sediments, being stable under anaerobic conditions. Denitrification occurs within anaerobic sediments near the redox discontinuity layer, whereas nitrification takes place in the aerobic surface layer and the oxygenated water column. As nitrification proceeds in the upper, oxidized sediments, nitrate is produced and diffuses across the redox discontinuity layer into the anaerobic zone. Denitrifying bacteria utilize the nitrate within this zone. Hence, intense microbial action at the redox discontinuity layer facilitates the downward movement of nitrate into the anaerobic zone, where denitrification occurs, and the upward diffusion of ammonium into the aerobic zone, where nitrification takes place.192 An important process affecting dissolved ammonium distribution in sediments is reversible adsorption on sedimentary particles.193
Enhanced removal of antibiotics using Eichhornia crassipes root biomass in an aerobic hollow-fiber membrane bioreactor
Published in Biofouling, 2022
Sevcan Aydin, Duygu Nur Arabacı, Aiyoub Shahi, Hadi Fakhri, Suleyman Ovez
The most dominant genus in all sludge samples was Arcobacter, known to contribute significantly to biofouling (Collado and Figueras 2011). Abundant in wastewater treatment facilities, this genus has also been reported to harbor pathogenic species and acquire antibiotic resistance (Zhu et al. 2017). Moreover, previous studies have reported that conventional wastewater treatment facilities have failed to completely remove Arcobacter spp., being also abundant in the effluents (Kristensen et al. 2020). In the presence of WHRB, the genus Arcobacter was almost completely eradicated compared with the antibiotic control. Thus, further investigation of WHRB bioaugmentation should be conducted in different types of wastewater treatment systems for wide application. Moreover, the genera Sedimentibacter and Tissierella, increased in the presence of antibiotics, suggesting tolerance, however, they isappeared completely with the addition of WHRB. This decrease in abundance may be attributed to these genera that normally thrive under anaerobic conditions being outcompeted by other microorganisms after WHRB alleviated the stress caused by the antibiotics. Furthermore, the increase in the aerobic denitrifying bacteria Dechloromonas and Leptothrix in the EC reactor also suggests possible bioaugmentation possibilities.
Spatial fractionation of phosphorus accumulating biofilm: stratification of polyphosphate accumulation and dissimilatory nitrogen metabolism
Published in Biofouling, 2022
Didrik Villard, Torgeir Saltnes, Gjermund Sørensen, Inga Leena Angell, Sondre Eikås, Wenche Johansen, Knut Rudi
The MiDAS database was used to link the identity of abundant microorganisms in the individual Hias biofilm fractions to their functional importance (Figure 4A). Denitrifying bacteria were found to be most abundant in the outermost layer, rapidly decreasing towards the deeper layers of the biofilm. In contrast, the abundance of phosphorus accumulating organisms (PAOs) was highest in the innermost layer and steadily decreased towards the biofilm surface. In general, glycogen-accumulating organisms (GAOs) and fermenters were found to be less dominant, especially at the biofilm surface, their relative contribution to the microbiome increasing towards the deeper layers of the biofilm.