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

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.The activated sludge process is the most popular method worldwide for the biological treatment of both municipal and industrial wastewaters. In conventional systems, solid-liquid phase separation is performed to produce ideally a final clear treated liquid effluent from the secondary settling tank 1 . Activated sludge bulking in the secondary settling tanks is a serious operational problem, which can lead to an outflow of suspended solids from the tank and decreasing biomass concentration in the reactor, resulting in a poor quality effluent, with poor thickening and dewatering characteristics 1 . Bulking is caused usually by excessive proliferation of filamentous bacteria, which appear to interfere with floc sedimentation and compaction 2 .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 . These methods provide only temporary relief. They are useful when the cause of the filamentous bulking cannot be determined immediately, and when rapid resolution of a bulking problem is necessary 3 . On the other hand, specific targeted control methods if available are more attractive since high performing plants can operate with a limited filament proliferation 3 . Although the problem of bulking has attracted considerable interest, conclusions as to which individual ecological and physiological factors might favor excessive filament growth are still not available 3 . Quantitative PCR (qPCR) assays have identified correlations between "Ca. Microthrix parvicella" 4-6 , Thiothrix eikelboomii 7,8 , Sphaerotilus natans 9 and Haliscomenobacter hydrossis 10 16 S rRNA gene copy numbers and sludge settleability. However, such quantitative studies are rare.

Physical Disturbance Reduces Cyanobacterial Relative Abundance and Substrate Metabolism Potential of Biological Soil Crusts on a Gold Mine Tailing of Central China

“…It is reported that Thermoanaerobacterium have strong resistance against UV light, heavy metals, and oxidative stress ( Rosenberg et al, 2014 ), thus the highest relative abundance of Thermoanaerobacterium in the present study was found in DH. Different from the biocrusts in drylands, filamentous bacterium Kouleothrix , the main filamentous bacteria for sludge bulking in sewage treatment plants ( Nittami et al, 2019 , 2020 ), was also found in this study, and this may be ascribed to the geographical location of this gold mine.…”

Recent advances in understanding the ecology of the filamentous bacteria responsible for activated sludge bulking

“…2020b; Nittami et al . 2020), and previously undefined filaments have been described by comparing corresponding changes in their relative abundances. For example, Trichococcus (Wang et al .…”

“…2018), Japan (Nittami et al . 2020), Singapore (Guo and Zhang 2012), and United States (Guo and Zhang 2012), usually where plant samples are collected regularly (each week) from the same plant at regular intervals, and populations identified using appropriate data bases. Of these, the MiDAS version 2/3 database (designed especially for wastewater plant communities (McIlroy et al .…”

“…Furthermore, we discuss our recent wider studies of filamentous bacteria in Japan (Nittami et al . 2017, 2019, 2020) and consider how their specific control can be based on their ecophysiology.…”

Granulation strategies applied to industrial wastewater treatment: from lab to full-scale

“…The main filamentous genera found were Thiothrix and Kouleothrix. Both organisms have been associated with serious bulking problems in (industrial) activated sludge plants (Nielsen et al 2000;Nittami et al 2020).…”