Phased-inline coagulation for low-pressure membranes in water and wastewater treatment: a review of fouling mitigation, process control, and water quality

ABSTRACT

Low-pressure membranes (LPM) are increasingly popular in water treatment due to their effective removal of microorganisms, pathogens, and protozoa. A more widespread implementation of LPMs in water treatment is prevented due to membrane fouling, which increases operating and maintenance costs. Coagulation pretreatment of the LPM feed water by continuous-inline coagulation (C-IN-C), which involves coagulant addition without particle separation prior to LPM filtration, is a commonly applied approach for fouling mitigation. Phased-inline coagulation (C-IN-P), a variant of C-IN-C where the coagulant is dosed inline for the initial portion of the filtration cycle, is the subject of increased interest due to the potential for significant cost savings through reduced coagulant usage. In this review, existing knowledge from pertinent publications regarding C-IN-P pretreatment of LPM feed waters is critically reviewed. Specifically, the C-IN-P approach is reviewed with emphasis placed on understanding fouling behaviour, process control, and the removal of organics. Available studies suggest that intermittent coagulant addition by C-IN-P pretreatment can achieve comparable fouling mitigation to C-IN-C, where coagulant is injected continuously. It has also been shown that C-IN-P can achieve similar removal of bulk organics measures to C-IN-C pretreatment for different water types, while also offering significant cost savings on coagulant. According to the knowledge gaps identified throughout the study, the manuscript concludes by outlining guidance on potential foci of future research.

GRAPHICAL ABSTRACT

KEYWORDS:

• Inline coagulation
• phased coagulation
• membrane fouling
• NOM removal
• low-pressure membrane

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data sharing is not applicable to this article as no new data was created or analysed in this study.

Additional information

Funding

This work was supported by the Natural Sciences and Engineering Research Council of Canada under grant RGPIN 2018–06571 and the Canada Graduate Scholarship-Doctoral (CGS-D) program.

Notes on contributors

Joseph D. Ladouceur

Joseph D. Ladouceur, EIT, is a Ph.D. Candidate at the University of Ottawa. He holds a bachelor’s degree in civil engineering from the University of Ottawa with Summa Cum Laude distinction. His research interests are primarily focused on applications of membranes for drinking water production. Specifically, Joseph is focused on pretreatment strategies for membrane fouling reduction, with an aim to make membrane processes more sustainable, economic, and adaptable to changing global water quality. Joseph is a registered EIT with Professional Engineers Ontario, a recipient of an NSERC Canada Graduate Scholarship, and the 2023 AMTA Ian C. Watson Fellow.

Roberto M. Narbaitz

Roberto M. Narbaitz, Ph.D., is an Emeritus Professor at the University of Ottawa. After completing his doctoral studies at McMaster University in 1985, Dr. Narbaitz joined the Dept. of Civil and Environmental Engineering at Florida International University, the State University of Florida at Miami. He joined the University of Ottawa in 1990 where he taught environmental engineering courses until his retirement in 2021. His research is currently focused on water treatment using membranes, the development of new membrane materials, activated carbon adsorption and ion exchange.

Christopher Q. Lan

Christopher Q. Lan, Ph.D., is a Professor at the University of Ottawa in the Dept. of Chemical and Biological Engineering. Dr. Lan received his Ph.D. in Biochemical Engineering at the Western University in June 2001. His research interests encompass microalgal biotechnology, biopharmaceuticals, separation technologies, membrane desiccant cooling, and thermodynamics. Professor Lan emphasises both fundamental and industry-oriented studies.