title: Identification of the function of extracellular polymeric substances (EPS) in denitrifying phosphorus removal sludge in the presence of copper ion.
abstract: Industrial wastewater containing heavy metals that enters municipal wastewater treatment plants inevitably has a toxic impact on biological treatment processes. In this study, the impact of Cu(II) (0, 1.5, 2, 2.5, 3 mg/L) on the performance of denitrifying phosphorus removal (DPR) and microbial community structures was investigated. Particularly, the dynamic change in the amount and composition of extracellular polymeric substances (EPS), and the role of EPS in P removal, were assessed using three-dimensional excitation-emission matrix fluorescence spectroscopy combined with parallel factor (PARAFAC) analysis. The results showed that, after long-term adjustment, the P removal efficiency was maintained at 95 ± 2.7% at Cu(II) addition up to 2.5 mg/L, but deteriorated when the Cu(II) addition was 3 mg/L. The EPS content, including proteins and humic substances, increased with increasing Cu(II) additions at concentrations ≤2.5 mg/L. This property of EPS was beneficial for protecting phosphate-accumulating organisms (PAOs) against heavy metals, as both proteins and humic substances are strong ligands for Cu(II). Therefore, the PAOs abundance was still relatively high (67 ± 3%) when Cu(II) accumulation in sludge was up to 10 mg/g SS. PARAFAC confirmed that aromatic proteins could be transformed into soluble microbial byproduct-like material when microorganisms were subjected to Cu(II) stress, owing to their strong metal ion complexing capacity. The increase in the percentage of humic-like substances enhanced the detoxification function of the sludge EPS. EPS accounted for approximately 26-47% of P removed by adsorption when Cu(II) additions were between 0 and 2.5 mg/L. The EPS function, including binding toxic heavy metals and P storage, enhanced the operating stability of DPR systems. This study provides us with a better understanding of (1) the tolerance of DPR sludge to copper toxicity and (2) the function of sludge EPS in the presence of heavy metals in biological P removal systems.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Siping Road, Shanghai 200092, PR China. Electronic address: yayi.wang@tongji.edu.cn.
authors.forename: Yayi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Siping Road, Shanghai 200092, PR China.
authors.forename: Jian
authors.initials: J
authors.lastname: Qin
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Siping Road, Shanghai 200092, PR China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Siping Road, Shanghai 200092, PR China.
authors.forename: Ximao
authors.initials: X
authors.lastname: Lin
authors.affiliation: School of Chemical Engineering, The University of Queensland, St Lucia, Brisbane 4072, Australia.
authors.forename: Liu
authors.initials: L
authors.lastname: Ye
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Siping Road, Shanghai 200092, PR China.
authors.forename: Chengkang
authors.initials: C
authors.lastname: Song
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Siping Road, Shanghai 200092, PR China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Yan
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D003300:Copper / Q000633:toxicity*; D058440:Denitrification; D005163:Factor Analysis, Statistical; D009930:Organic Chemicals / Q000378:metabolism; D010758:Phosphorus / Q000737:chemistry*; D011108:Polymers / Q000378:metabolism*; D012722:Sewage / Q000032:analysis; D013050:Spectrometry, Fluorescence; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000382:microbiology; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D003300:Copper; D009930:Organic Chemicals; D010758:Phosphorus; D011108:Polymers; D012722:Sewage; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Cu(II); Denitrifying phosphorus removal; Excitation–emission matrix fluorescence spectroscopy; Extracellular polymeric substances; P-accumulating organisms