Identity and ecophysiology of filamentous bacteria in activated sludge

Abstract

Excessive growth of filamentous bacteria in activated sludge wastewater treatment plants (WWTPs) can cause serious operational problems. With some filaments there may be the problem of bulking, where inadequate flocculation and settling of the biomass in the secondary clarifier results in a carryover of solids with the final treated liquid effluent. Their proliferation often encourages the development of stable foams on the surface of the reactors, and these foams may impact negatively on plant performance and operation. The availability of culture-independent molecular methods now allows us to identify many of the more common filamentous organisms encountered in WWTPs, which are phylogenetically diverse, affiliating to seven separate bacterial phyla. Furthermore, the extensive data published in the past decade on their in situ behaviour from the application of these culture-independent methods have not been summarized or reviewed critically. Hence, here, we attempt to discuss what we now know about their identity, ecophysiology and ecological niches and its practical value in better managing activated sludge processes. Some of this knowledge is already being applied to control and manage full-scale WWTPs better, and the hope is that this review will contribute towards further developments in this field of environmental microbiology.

Detailed comparison of bacterial communities during seasonal sludge bulking in a municipal wastewater treatment plant

“…For example, more than 30 different filament morphotypes were found in AS systems and their excessive growth was associated with sludge bulking (Nielsen et al, 2009). Among them, members of Actinobacteria such as Candidatus M. parvicella and Tetrasphaera were often the causative organisms of sludge bulking by plant surveys conducted around the world (Martins et al, 2004;Seviour et al, 2008).…”

“…Other filamentous members, such as Eikelboom morphotype 0803 of Chloroflexi, have also been found in AS WWTPs, and they have occasionally been associated with bulking incidences (Beer et al, 2002;Bj€ ornsson et al, 2002;Speirs et al, 2015). Moreover, the filamentous species of Bacteroidetes such as Haliscomenobacter hydrossis and Firmicutes such as Trichococcus Nostocoida limicola I have been isolated from AS (Nielsen et al, 2009;Liu et al, 2000;Muszynski, 2016), and they may have a slight effect on biomass settling properties . In fact, different types of filamentous bacteria may exist in WWTPs with or without obvious sludge bulking.…”

“…Among them, members of Actinobacteria such as Candidatus M. parvicella and Tetrasphaera were often the causative organisms of sludge bulking by plant surveys conducted around the world (Martins et al, 2004;Seviour et al, 2008). In addition to Actinobacteria, members of Proteobacteria such as Meganema perideroedes, Thiothrix eikelboomii, Leucothrix mucor, and type 021N (Nielsen et al, 2009;Asvapathanagul et al, 2015) could cause sludge bulking. Other filamentous members, such as Eikelboom morphotype 0803 of Chloroflexi, have also been found in AS WWTPs, and they have occasionally been associated with bulking incidences (Beer et al, 2002;Bj€ ornsson et al, 2002;Speirs et al, 2015).…”

“…Substantial studies related to filamentous bulking have mainly focused on the ecophysiology of filamentous bacteria (Nielsen et al, 2009). For example, more than 30 different filament morphotypes were found in AS systems and their excessive growth was associated with sludge bulking (Nielsen et al, 2009).…”

Development and evaluation of a TaqMan duplex real-time PCR quantification method for reliable enumeration of Candidatus Microthrix

“…Moreover, using mulitplex PCR, simultaneous detection of total Bacteria or other problematic species such as Eikelboom's types (021N, 0675, 0041, 0961, 1701, 0914 and 0092), Thiothrix eikelboomii, Nostocoida limocola, and Gordonia amarae, etc. would be possible (Dumonceaux et al, 2006;Jenkins et al, 2004;Marrengane et al, 2011;Nielsen et al, 2009;Seviour et al, 1994;Vervaeren et al, 2005). However, the development of a multiplex qPCR using the same gene is difficult due to the competition for resources.…”