Production of protein‐ and carbohydrate‐EPS in activated sludge reactors operated at different carbon to nitrogen ratios

Abstract

BACKGROUND This study aimed to clarify how a variation in the carbon to nitrogen (C/N) ratio in influent wastewater affects the production and composition of extracellular polymeric substances (EPS) in activated sludge. In the literature such a comparative analysis is rarely presented, most studies on EPS focus on simultaneous organic carbon removal and nitrification whereas little attention is paid to the case of low organic load or separate‐stage nitrification. RESULTS Among the very loosely bound, loosely bound and tightly bound EPS fractions, tightly bound EPS prevailed in semi‐continuously fed batch activated sludge reactors that were fed at a C/N ratio of 10, 5 and 0, respectively. The C/N ratio had no clear effect on total EPS production, however it changed the proportion of proteins and carbohydrates. In each sludge proteins constituted the dominant part of EPS, but the EPS of the nitrifying sludge (C/N = 0), had a definitely higher protein content. As evidenced by HPSEC fingerprints, in all EPS fractions most proteins had MWs ≤16 kDa. Depending on the C/N ratio in a reactor, high MW proteins in EPS shifted from tightly bound fractions to others. CONCLUSION The study is among the few that highlight how the protein and carbohydrate content in EPS changes at different C/N ratios. Since wastewater composition in a treatment system affects the chemical composition of EPS, each sludge might have different responses to uptake of xenobiotics such as metals. Further, this difference in composition might affect sludge settling, dewatering and membrane fouling. © 2014 Society of Chemical Industry

Beneficial effects of treating waste secondary sludge with thermally activated persulfate

“…Extraction of EPSs from the sludge was done according to the procedure developed by Geyik and Çeçen . The soluble EPSs (or slime EPSs; S‐EPSs) were determined after centrifugation (Beckman Coulter, Allegra 64R High Speed Refrigerated Centrifuge) of the sludge at 12 000 g for 10 min.…”

“…Extraction of EPSs from the sludge was done according to the procedure developed by Geyik and Çeçen. 34 The soluble EPSs (or slime EPSs; S-EPSs) were determined after centrifugation (Beckman Coulter, Allegra 64R High Speed Refrigerated Centrifuge) of the sludge at 12 000 g for 10 min. The bound EPSs were classified as very loosely bound-EPS (VLB-EPS), loosely bound-EPS (LB-EPS), and tightly bound-EPS (TB-EPS) fractions.…”

Effects of COD/N ratio on soluble microbial products in effluent from sequencing batch reactors and subsequent membrane fouling

“…They are mostly produced during biomass growth (utilization-associated products; UAPs) and/or cell lysis during biomass decay (biomass-associated products; BAP) (Michael-Kordatou et al 2015). The characteristics of SMP are dependent upon several biological treatment parameters such as organic composition of influent wastewater (Geyik and Çeçen 2016, Hao et al 2016, Ye et al 2011, solid retention time (SRT) (Esparza-Soto et al 2011, Jarusutthirak andAmy 2007), organic loading rate (OLR) (Maqbool et al 2017), and dissolved oxygen content (Maqbool et al 2016).…”

Inhibitory effect of silver on activated sludge: effect of organic substrate and the carbon to nitrogen ratio

“…Certainly, sludge characteristics such as EPS composition and surface character may play a role in inhibition. Our previous studies clearly revealed the differences in EPS of R1, R2 and R3 sludges . As will be reported later, in a complementary study we examined also the composition and fractionation of EPS as well as hydrophobicities and surface charges.…”