Abstract
A large amount of phosphorus was found in the extracellular polymeric substances (EPS) of activated sludge used in enhanced biological phosphorus removal (EBPR), so the role of EPS and extracellular phosphorus in EBPR should not be neglected. The composition and properties of tightly bound EPS (TB-EPS) and loosely bound EPS (LB-EPS) were significantly different, and it was necessary to study the adsorption performance of EPS through the fractionating of activated sludge into LB-EPS, TB-EPS and microbial cells. In this study, the adsorption performance of LB-EPS and TB-EPS for phosphate was explored by extracting LB-EPS and TB-EPS via sonication and cation exchange resin (CER), respectively. The results indicated that the sonication-CER method was an efficient and reliable extraction method for EPS with a synergistic effect. The performance of EPS in the adsorption/complexing of phosphate was excellent because of its abundant functional groups. Specifically, the type and content of metal elements and functional groups in TB-EPS were much greater than those in LB-EPS, which led to the key role of TB-EPS in the adsorption/complexing of phosphate. Finally, a metabolic model for EBPR with consideration of the adsorption performance of LB-EPS and TB-EPS was proposed.
Highlights
Extracellular polymeric substances (EPS) are widely distributed in biological aggregates, which has an important influence on the wastewater biological treatment process [1,2]
tightly bound EPS (TB-EPS) for phosphate was explored by extracting loosely bound EPS (LB-EPS) and TB-EPS via sonication and cation exchange resin (CER), respectively
Microbial cells are embedded within EPS, which can be divided into tightly bound EPS (TB-EPS) located in the inner layer of the sludge floc and loosely bound EPS (LB-EPS)
Summary
Extracellular polymeric substances (EPS) are widely distributed in biological aggregates, which has an important influence on the wastewater biological treatment process [1,2]. In the past two decades, EPS have been shown to contain a large amount of phosphorus, which is the phosphorus storage and transfer station in the enhanced biological phosphorus removal (EBPR) process [3]. The role of EPS in the EBPR process is nonnegligible and should be considered in the mechanisms of phosphorus removal. Microbial cells are embedded within EPS, which can be divided into tightly bound EPS (TB-EPS) located in the inner layer of the sludge floc and loosely bound EPS (LB-EPS). Existing in the outer layer of the sludge floc [1,4]. The contents, compositions and properties of TB-EPS and LB-EPS were found to be different [5,6,7], and their influences on the flocculation, sedimentation and dewatering of activated sludge were significantly different. To acquire more information about the exact role of EPS in EBPR, it is necessary to fractionate EPS into TB-EPS and LB-EPS
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