Thiothrix eikelboomii interferes oxygen transfer in activated sludge

Xianwei Wu; Ju Huang; Zichuan Lu; Gaofeng Chen; Jianmin Wang; Guoqiang Liu

doi:10.1016/j.watres.2018.12.019

Thiothrix eikelboomii interferes oxygen transfer in activated sludge

Water Res. 2019 Mar 15:151:134-143. doi: 10.1016/j.watres.2018.12.019. Epub 2018 Dec 20.

Authors

Xianwei Wu¹, Ju Huang¹, Zichuan Lu¹, Gaofeng Chen¹, Jianmin Wang², Guoqiang Liu³

Affiliations

¹ School of Environment, Guangdong Engineering Research Center of Water Treatment Processes and Materials, And Guangdong Key Laboratory of Environmental Pollution and Health, Jinan University, Guangzhou, 510632, China.
² Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla, MO, 65409, USA.
³ School of Environment, Guangdong Engineering Research Center of Water Treatment Processes and Materials, And Guangdong Key Laboratory of Environmental Pollution and Health, Jinan University, Guangzhou, 510632, China. Electronic address: gqliu@jnu.edu.cn.

PMID: 30594082
DOI: 10.1016/j.watres.2018.12.019

Abstract

This study revealed that, Thiothrix eikelboomii, a well-known filamentous bacterium that causes sludge bulking, could also interfere oxygen transfer during wastewater treatment. The volumetric oxygen transfer coefficient (K_La) in filamentous-bulking sludge (FBS) was found to be 43% lower than that in floc-forming sludge (FFS) at similar biomass concentrations, partially because the filamentous bacteria had increased the sludge apparent viscosity. The K_La value for FBS, however, was still significantly lower than that for FFS even if both sludges had similar apparent viscosity. Numerous tiny and free-swimming filaments were observed to attach on the air bubble surface, presumably reducing the liquid film renewal and increasing the liquid film thickness. Moreover, the filaments were co-coated with extracellular polymeric substances of protein and polysaccharide, which could make them performing like "amphiphilic molecules" of surfactants to hinder oxygen transfer. Therefore, the particular surface property of filaments and their interaction with air bubbles could also impact oxygen transfer. Thiothrix eikelboomii was identified to be the responsible filamentous bacterium that lowered the K_La value, while other filamentous bacteria with short filaments did not interfere oxygen transfer. This study implies that controlling sludge bulking benefits not only sludge settling but also oxygen transfer.

Keywords: Activated sludge; Filamentous bulking; Oxygen transfer; Thiothrix; Wastewater treatment.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Oxygen
Sewage*
Thiothrix*
Waste Disposal, Fluid
Wastewater

Substances

Sewage
Waste Water
Oxygen