The microbial community in filamentous bulking sludge with the ultra-low sludge loading and long sludge retention time in oxidation ditch

Abstract

Sludge bulking is a major problem that restricts the development of the activated sludge process. The microbial community responsible for sludge bulking varies depending on water quality and operational conditions. This study analysed the microbial community of bulking sludge in oxidation ditch with ultra-low sludge loading and long sludge retention time using high-throughput sequencing. The study found that the relative abundance of bacterial genus Saprospiraceae_norank was the highest in bulking sludge, reaching 13.39–28.83%, followed by Comamonadaceae_unclassified, Ardenticatenia_norank and Tetrasphaera, with the relative abundance of 4.59–11.08%, 0.52–16.60% and 0.17–8.92% respectively. In contrast, the relative abundance of bacteria that easily caused sludge bulking including Microthrix (0.54–2.47%), Trichococcus (0.32–1.71%), Gordonia (0.14–1.28%), and Thiothrix (0.01–0.06%) were relatively low. Saprospiraceae_norank was predominant and induced sludge bulking in oxidation ditch. The relative abundance of fungal genus Trichosporon was the highest in bulking sludge, reaching 16.95–24.98%, while other fungal genera were Saccharomycetales_unclassified (5.59–14.55%), Ascomycota_norank (1.45–13.51%), Galactomyces (5.23–11.23%), and Debaryomyces (7.69–9.42%), whereas Trichosporon was the dominant fungal genus in bulking sludge. This study reported that excessive Saprospiraceae_norank can induce sludge bulking for the first time, which provides important knowledge to control sludge bulking.

Candidatus Amarolinea and Candidatus Microthrix Are Mainly Responsible for Filamentous Bulking in Danish Municipal Wastewater Treatment Plants

“…The development of culture-independent molecular methods has facilitated more reliable identification and description of the diversity of filamentous bacteria present in the activated sludge environment. Fluorescence in situ hybridization (FISH) and 16S rRNA amplicon sequencing have been applied to survey microbial communities in activated sludge to identify and characterize filamentous bacteria common in this ecosystem (Mielczarek et al, 2012;Araújo Dos Santos et al, 2015;Milobędzka and Muszyński, 2015;Jiang et al, 2016;Saunders et al, 2016;Wang et al, 2016;Zhang et al, 2019). Filamentous genera found therein span several phyla, i.e., Actinobacteria (Rossetti et al, 2005), Bacteroidetes (Van Veen et al, 1973;Kragelund et al, 2008), Chloroflexi (Speirs et al, 2009;McIlroy et al, 2016), Firmicutes (Liu et al, 2000), Planctomycetes and Proteobacteria (Kragelund et al, 2005(Kragelund et al, , 2006.…”

Pseudonocardia filamentous bulking sludge in an industrial wastewater treatment plant as revealed by Illumina amplicon sequencing

“…Needle-like thin filaments identified with FISH (probe SAP309,Saprospiraceae) were also ranked as abundant (FI 5). Zhang et al (2019) found that the relative abundance of Saprospiraceae was the highest in oxidation ditcheswith long sludge retention time. The family Saprospiraceae includes the genera Phaeodactylibacter, Saprospira, Haliscomenobacter, Lewinella, Portibacter, Aureispira and Rubidimonas (Chen et al, 2014).…”

“…Factors such as water temperature, dissolved oxygen, sludge retention time, pH, influent quality, sludge loading rate and nutrients ratio are responsible for filamentous sludge bulking (Zhang et al 2019). The most important differences between samples S1 and S2 were a significant decrease in nutrients (P and N) when Pseudonocardia sp.…”

Study on Propellers Distribution and Flow Field in the Oxidation Ditch Based on Two-Phase CFD Model

“…To develop a deeper understanding of relationships between velocity and locations, the characteristics of the flow field in scheme (b) were analyzed, both experimentally and numerically. This is illustrated in Figure 13 by using six sections (1)(2)(3)(4)(5)(6).…”

“…Therefore, they are one of the most widely used methods for activated sludge biological treatment [4]. Despite the existing research recognizes the critical role played by OD in the treatment plant's production effectiveness and economics, old and inefficient technology still prevails in many OD systems; thus, studies suggest their modernization will enhance the flow field and reduce costs and environmental impact [5][6][7][8].…”