QUYong,ZHANGYan,WANGYuanyuan,et al.Causes of Viscous Sludge Bulking in Urban Wastewater Treatment Plants[J].China Water & Wastewater,2026,42(3):95-102.
Causes of Viscous Sludge Bulking in Urban Wastewater Treatment Plants
China Water & Wastewater[ISSN:1000-4062/CN:12-1073/TU]
volume:
第42卷
Number:
第3期
Page:
95-102
Column:
Date of publication:
2026-02-01
- Keywords:
- wastewater treatment plant; viscous sludge bulking; extracellular polymeric substances (EPS); sludge settleability; organic loading
- Abstract:
- To investigate the causes of viscous bulking of activated sludge, a one?year monitoring study was carried out at a wastewater treatment plant during a viscous bulking episode. Variations of extracellular polymeric substances (EPS), sludge settling performance, and microbial community structure were analyzed. In addition, sequencing batch reactor experiments were conducted to examine the effects of temperature variation on electron transfer activity and sludge settleability under three different organic loading conditions. The results indicated that viscous sludge bulking was significantly influenced by temperature changes. As the temperature decreased from 25 ℃ to 10 ℃, the electron transfer activity declined from 147 mg/(gVSS·h) to 30 mg/(gVSS·h), while the EPS content increased from 90 mg/gVSS to 133 mg/gVSS. The decrease in temperature slowed microbial metabolic rates, stimulating greater EPS secretion. Furthermore, the addition of an external carbon source promoted excessive proliferation of methylotrophic bacteria, which reached a relative abundance of 11.9%, leading to microbial community imbalance and functional disturbance, thereby further increasing EPS production. High organic loading enhanced microbial metabolism and electron transport chain activity, resulting in elevated EPS secretion. This caused the sludge flocs to become structurally loose and less dense, ultimately impairing sludge settling performance and inducing viscous sludge bulking.
Last Update:
2026-02-01