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Membrane Bioreactor for Perchlorate Treatment
Published in Amitava Rakshit, Manoj Parihar, Binoy Sarkar, Harikesh B. Singh, Leonardo Fernandes Fraceto, Bioremediation Science From Theory to Practice, 2021
Benny Marie B. Ensano, Sivasankar Annamalai, Yeonghee Ahn
Limited oxygen supply can significantly improve perchlorate degradation in CH4 -based MBfR due to the formation of volatile fatty acids (VFAs), which help drive perchlorate reduction even at shorter HRT. VFAs are intermediate products of methane partial oxidation by methanogens (Methanosarcina) and fermenters (Veillonellaceae). VFAs such as acetic acid and propionic acid can be utilized by PRB (Denitratisoma and Rhodocyclaea) for heterotrophic perchlorate degradation (Wu et al. 2019). When no oxygen is supplied (anoxic condition), perchlorate reduction can still be achieved, although minimally, via the synergistic interactions of aerobic methanotrophs (Methylocystaceae and Methylococcaceae) and PRB (Denitratisoma and Rhodocyclaceae). The aerobic methanotrophs use the oxygen produced from the chlorite dismutation by PRB and in return, methanotrophs oxidize methane and produce intermediates that are utilized by PRB as electron donors in degrading perchlorate. However, the O2 released by PRB might not be sufficient to aerobic methanotrophs, hence the need for external limiting O2 supply (Wu et al. 2019).
Long-term dynamics of the bacterial community in a Swedish full-scale wastewater treatment plant
Published in Environmental Technology, 2019
Nils Johan Fredriksson, Malte Hermansson, Britt-Marie Wilén
To characterize the bacterial community in the activated sludge, 16S rRNA gene libraries were generated from three samples collected at different times: early winter (11/07/2003), late winter (02/26/2004) and summer (07/15/2004). The libraries included 49 (11/07/2003), 65 (02/26/2004) and 63 (07/15/2004) sequences, and the estimated coverage at species level was 66%, 30% and 58%. In all three samples, the retrieved sequences were dominated by Proteobacteria, with Alphaproteobacteria being the most abundant (Figure 1, panel A). However, within the phyla, there were some differences between the samples (Figure 1, panel B). Most Alphaproteobacteria sequences in all three libraries were classified as Rhizobiales or Rhodobacterales, but the proportions of the two orders varied. For example, the order Rhizobiales was nearly absent in the sample collected 02/26/2004, but it was the most abundant in the sample from 07/15/2004. The Rhodobacterales sequences were classified as Rhodobacteraceae, which include heterotrophs and phototrophs found in many different environments, including freshwater and seawater [43], clinical samples [44], sediments [45], soil [46], wastewater ditches [47] and activated sludge [48]. The sequences of Rhizobiales were classified as Beijerinckiaceae (which are nitrogen-fixing heterotrophs found in soil [49,50]), Hyphomicrobiaceae (heterotrophic and methylotrophic bacteria found in soil [51,52]) and Methylocystaceae (type II methanotrophs isolated from wetlands [53] and aquifers [54]). Most Alphaproteobacteria found at the Rya WWTP were highly similar to sequences retrieved from other environments, such as bioreactors, soils, sediments, human skin and digestive tract (See Table S2, BLAST search).