Exploring the operating factors controlling Kouleothrix (type 1851), the dominant filamentous bacterial population, in a full-scale A2O plant

Tadashi Nittami,Yusuke Koshiba,Tomohiro Tobino,Kota Suzuki,Risa Kasakura,Minoru Takeda,Daniel Rice,Toshimasa Kobayashi,Steve Petrovski,Futoshi Kurisu,Robert J Seviour,Junji Fukuda

doi:10.1038/s41598-020-63534-2

Abstract

This study reveals that the abundance of the filament Kouleothrix (Eikelboom type 1851) correlated positively with poor settleability of activated sludge biomass in a Japanese full-scale nutrient removal wastewater treatment plant sampled over a one-year period. 16S rRNA amplicon sequence data confirmed that Kouleothrix was the dominant filament in the plant, with a relative abundance of 3.06% positively correlated with sludge volume index (SVI) (R = 0.691). Moreover, Kouleothrix (type 1851) appeared to form interfloc bridges, typical of bulking sludge, regardless of season. Together with earlier studies that indicated the responsibility of Kouleothrix (type 1851) on bulking events, these data suggest that their high relative abundances alone may be responsible for sludge bulking. 16S rRNA qPCR data for this filament showed changes in its relative abundance correlated with changes in several operational parameters, including mixed liquor temperature, sludge retention time, and suspended solids concentration, and it may be that manipulating these may help control Kouleothrix bulking.

Highlights

This study reveals that the abundance of the filament Kouleothrix (Eikelboom type 1851) correlated positively with poor settleability of activated sludge biomass in a Japanese full-scale nutrient removal wastewater treatment plant sampled over a one-year period. 16S rRNA amplicon sequence data confirmed that Kouleothrix was the dominant filament in the plant, with a relative abundance of 3.06% positively correlated with sludge volume index (SVI) (R = 0.691)
These data show that Kouleothrix was dominant, with a relative abundance of 3.06%, followed by Tetrasphaera sp., “Ca. Defluviifilum”, and Gordonia sp. with percentage relative abundances of 1.11%, 0.88%, and 0.60%, respectively
All values were less than 10, indicating that there was no multicollinearity for these independent variables. These data as expected indicate that, increasing the SS, SRT, and return sludge SS values leads to an increase in the Kouleothrix 16 S rRNA gene copy number, which in turn negatively correlates with the mixed liquor temperature. This present study aimed to investigate more closely the relationship between Kouleothrix filamentous bacteria abundances and SVI in a Japanese A2O process treating domestic wastewater

Summary

Introduction

Existing filamentous bulking control methods can be considered as specific and non-specific[3] The latter usually consist of adding chemicals, including oxidizing agents (chlorine, ozone, hydrogen peroxide), weighting and flocculating agents (salts of iron and aluminium, lime, polymers and talc), and biocides[3]. We have shown that relative percentage abundances of type 1851/ Kouleothrix had a quantitative linear relationship with biomass settleablity in several municipal wastewater treatment plants (WWTPs) in Yokohama, especially during the summer months[11] More recently this approach has been extended to quantify Kouleothrix in 11 municipal WWTPs across Japan, and the data generated confirmed that increases in their abundances corresponded to sludge bulking episodes[12]. N&P processes had the highest average copy number (1.01 × 105 16S rRNA gene copies ng-DNA−1) but with the highest standard deviations (7.67 × 104) Such trends seemed to suggest that relative abundances of Kouleothrix spp. in N&P removal may reflect plant operating conditions

Methods

Results

Conclusion