Understanding the evolution of stratified extracellular polymeric substances in full-scale activated sludges in relation to dewaterability

Abstract

Activated sludge is a highly changeable colloidal system. In this study, the dynamic variation in physicochemical characteristics, especially distribution and abundance of extracellular polymeric substances (EPS) of activated sludges from different WWTPs was investigated in order to establish the relationships between floc properties and the sludge dewatering property. Firstly, it was observed that the total EPS content of the activated sludge was significantly decreased with the rise in temperature.Three-dimensional fluorescence excitation-emission matrix (3D-EEM) spectroscopy analysis indicated that each sludge fraction (soluble EPS, loosely-bound EPS (LB-EPS), tightly bound EPS (TB-EPS) and pellet) from different WWTPs had a similar fluorescence fingerprint in the same time period. In addition, protein-like substances were found to be the dominant components in TB-EPS and pellets regardless of operating time for each WWTP sludge. At low temperatures, soluble EPS and LB-EPS also mainly contained protein-like compounds, while the amount of humic acids of them was increased significantly in the summer. According to Pearson's correlation analysis, normalized CST correlated well with the composition and content of soluble EPS, indicating that the change in soluble EPS properties caused fluctuation of sludge dewatering behavior. Finally, we proposed some operating strategies for improving the dewatering performance of activated sludge in full-scale WWTPs by regulating the soluble EPS properties.Correlation is signicant at the 0.05 level (2-tailed). bCorrelation is signicant at the 0.01 level (2-tailed). c SEPS-soluble EPS, LB-LB-EPS, TB-TB-EPS, S1-region I of soluble EPS, S2-region II of soluble EPS, S3-region III of soluble EPS, S4-region IV of soluble EPS,.This journal is

Enhancement of waste activated sludge dewaterability using calcium peroxide pre-oxidation and chemical re-flocculation

“…The results were in agreement with the analysis of DOC variation previously that protein-like organic matters in TB-EPS component transformed to LB-EPS and SEPS. As a result, the increase in concentrations of protein-like substances caused deterioration of sludge filtration dewatering performance (Zhang et al, 2015b).…”

Wastewater sludge dewaterability enhancement using hydroxyl aluminum conditioning: Role of aluminum speciation

“…5 can see that the TB-EPS concentrations conditioned by Al 13 and PAC 2.5 increased again comparing to other aluminum salt coagulants, this also indicated that Al b and Al c showed better performance in compressing EPS structure than Al a , which made SEPS and LB-EPS transfer into TB-EPS, so TP-EPS conditioned by Al 13 and PAC 2.5 increased when SEPS and LB-EPS concentration conditioned by Al 13 and PAC 2.5 decrease, so their TB-EPS concentration was increased. Many studies have demonstrated that sludge filtration property was mainly dependent on properties of SEPS fraction, and the high content of protein in SEPS was always detrimental to sludge filterability (Zhang et al, 2014a(Zhang et al, , 2014b(Zhang et al, , 2015b. In addition, reduction of SEPS concentration contributed to improvement of sludge filterability, it was obvious that PAC with high alkalinity and Al 13 were more effective in removal of SEPS.…”

“…Now, chemical conditioning of sludge prior to mechanical dewatering is often necessary to enhance the operating efficiency of dewatering device. Addition of traditional chemical conditioners (inorganic salt coagulants and organic polymers) can agglomerate fine sludge colloids to form large flocs through charge neutralization and bridging, which can be more easily separated from the water (Niu et al, 2013;Zhang et al, 2014a) The most commonly inorganic flocculants in water and wastewater treatment are aluminum and iron salts. It is well known that aluminum speciation has important effects on its coagulation and flocculation ability.…”

Improvement of wastewater sludge dewatering performance using titanium salt coagulants (TSCs) in combination with magnetic nano-particles: Significance of titanium speciation

“…(Zhang et al, 2015b). Many studies have demonstrated that sludge filtration property was mainly dependent on properties of soluble EPS fraction, and the high content of protein in soluble EPS was always detrimental to sludge filterability (Zhang et al, 2014b(Zhang et al, , 2015c(Zhang et al, , 2015d. In addition, reduction of soluble EPS concentration contributed to improvement of sludge filterability, it was obvious that TSC 0.5 was more effective in removal of soluble EPS fraction.…”

“…Furhter, Yu et al (2008) demonstrated that soluble EPS also played an important role in sludge dewatering process. Zhang et al (2015a) suggested that change in concentration and compostion of soluble EPS fraction caused fluctuation of sludge dewatering behavior with time.…”