Effects of extracellular polymeric substance fractions on polyacrylamide demand and dewatering performance of digested sludges

To, VHP; Nguyen, TV; Bustamante, H; Vigneswaran, S

Effects of extracellular polymeric substance fractions on polyacrylamide demand and dewatering performance of digested sludges

To, VHP Nguyen, TV Bustamante, H Vigneswaran, S

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Publication Type:: Journal Article
Citation:: Separation and Purification Technology, 2020, 239
Issue Date:: 2020-05-15

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Field	Value	Language
dc.contributor.author	To, VHP	en_US
dc.contributor.author	Nguyen, TV	en_US
dc.contributor.author	Bustamante, H	en_US
dc.contributor.author	Vigneswaran, S https://orcid.org/0000-0002-8117-4322	en_US
dc.date.issued	2020-05-15	en_US
dc.identifier.citation	Separation and Purification Technology, 2020, 239	en_US
dc.identifier.issn	1383-5866	en_US
dc.identifier.uri	http://hdl.handle.net/10453/138244
dc.description.abstract	© 2020 Elsevier B.V. High polymer demand in sludge conditioning is an intractable aspect of the water industry. This study investigated the effects of extracellular polymeric substances (EPS) fractions on polyacrylamide demand for conditioning and dewatering performance. Specifically, it examined aerobically and anaerobically digested sludges from seven full-scale wastewater treatment plants (WWTPs). Our study successfully quantified the contributions of soluble EPS to polyacrylamide demand during conditioning and explained the role of tightly bound EPS (TB-EPS) in determining the digested sludges’ dewatering performance. Results show that the concentrations of soluble EPS in the sludges varied between 92 and 1148 mg/L. Experimental results also demonstrated that between 25% and 80% of polyacrylamides used for conditioning were wasted in “parasitic” reactions with soluble EPS. The residual cationic polyacrylamide left in solution, after the parasitic reactions, was substantial and varied between 35 and 254 mg/L. Despite this outcome, the zeta potential values of dewatered sludge cakes remained negative, i.e. between −24 and −35 mV. These indicated that the residual soluble cationic polyacrylamides would not have been absorbed on the negatively charged sludge particles. This explained the relatively poor performance of the dewatering stage in the treatment plants studied. Furthermore the results suggested the TB-EPS attached to the sludge particles would be responsible for the poor dewatering. We postulated that the TB-EPS would gelify and immobilize the water surrounding the sludge particles. Our study suggested that new and more effective polymers for conditioning are needed to both: (i) reduce polymer demand; and (ii) improve the dewatering performance.	en_US
dc.relation.ispartof	Separation and Purification Technology	en_US
dc.relation.isbasedon	10.1016/j.seppur.2020.116557	en_US
dc.rights	info:eu-repo/semantics/embargoedAccess
dc.subject.classification	Chemical Engineering	en_US
dc.title	Effects of extracellular polymeric substance fractions on polyacrylamide demand and dewatering performance of digested sludges	en_US
dc.type	Journal Article
utslib.citation.volume	239	en_US
utslib.for	0301 Analytical Chemistry	en_US
utslib.for	0904 Chemical Engineering	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology/School of Civil and Environmental Engineering
pubs.organisational-group	/University of Technology Sydney/Strength - CTWW - Centre for Technology in Water and Wastewater Treatment
utslib.copyright.status	open_access	*
utslib.copyright.embargo	2022-01-13T00:00:00+1100
pubs.publication-status	Accepted	en_US
pubs.volume	239	en_US

Abstract:

© 2020 Elsevier B.V. High polymer demand in sludge conditioning is an intractable aspect of the water industry. This study investigated the effects of extracellular polymeric substances (EPS) fractions on polyacrylamide demand for conditioning and dewatering performance. Specifically, it examined aerobically and anaerobically digested sludges from seven full-scale wastewater treatment plants (WWTPs). Our study successfully quantified the contributions of soluble EPS to polyacrylamide demand during conditioning and explained the role of tightly bound EPS (TB-EPS) in determining the digested sludges’ dewatering performance. Results show that the concentrations of soluble EPS in the sludges varied between 92 and 1148 mg/L. Experimental results also demonstrated that between 25% and 80% of polyacrylamides used for conditioning were wasted in “parasitic” reactions with soluble EPS. The residual cationic polyacrylamide left in solution, after the parasitic reactions, was substantial and varied between 35 and 254 mg/L. Despite this outcome, the zeta potential values of dewatered sludge cakes remained negative, i.e. between −24 and −35 mV. These indicated that the residual soluble cationic polyacrylamides would not have been absorbed on the negatively charged sludge particles. This explained the relatively poor performance of the dewatering stage in the treatment plants studied. Furthermore the results suggested the TB-EPS attached to the sludge particles would be responsible for the poor dewatering. We postulated that the TB-EPS would gelify and immobilize the water surrounding the sludge particles. Our study suggested that new and more effective polymers for conditioning are needed to both: (i) reduce polymer demand; and (ii) improve the dewatering performance.

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http://hdl.handle.net/10453/138244