Comparing the growth and structure of flocs from electrocoagulation and chemical coagulation

Lee, Sin Yin; Gagnon, Graham A.

doi:10.1016/j.jwpe.2016.01.012

Cited by 43 publications

(14 citation statements)

References 24 publications

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“…[396,397]. Two main coagulation processes are available which are chemical coagulation and electrocoagulation (EC) [398]. Flocculation follows coagulation which is usually referred to as a slow mixing step of the microflocs that leads to the formation visible particles that can be removed by sedimentation (through gravitational force), flotation, or filtration [145].…”

Section: Coagulation-flocculationmentioning

confidence: 99%

Reverse osmosis desalination: A state-of-the-art review

et al. 2019

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Water scarcity is a grand challenge that has always stimulated research interests in finding effective means for pure water production. In this context, reverse osmosis (RO) is considered the leading and the most optimized membrane-based desalination process that is currently dominating the desalination market. In this review, various aspects of RO desalination are reviewed. Theories and models related to concentration polarization and membrane transport, as well as merits and drawbacks of these models in predicting polarization effects, are discussed. An updated review of studies related to membrane modules (plate and frame, tubular, spiral wound, and hollow fiber) and membrane characterization are provided. The review also discusses membrane cleaning and different pre-treatment technologies in place for RO desalination, such as feed-water pre-treatment and biocides. RO pre-treatment technologies, which include conventional (e.g., coagulationflocculation, media filtration, disinfection, scale inhibition) and non-conventional (e.g., MF, UF, and NF) are reviewed and their relative attributes are compared. As per the available literature, UF, MF and coagulation-flocculation are considered the most widely used pre-treatment technologies. In addition, this review discusses membrane fouling, which represents a serious challenge in RO processes due to its significant contribution to energy requirements and process economy (e.g., flux decline, permeate quality, membrane lifespan, increased feed pressure, increased pre-treatment and membrane maintenance cost). Different membrane fouling types, such as colloidal, organic, inorganic, and biological fouling, are addressed in this review. Principles of RO process design and the embedded economic and energy considerations are discussed. In general, cost of water desalination has dropped to values that made it a viable option, comparable even to conventional water treatment methods. Finally, an overview of hybrid RO desalination processes and the current challenges faced by RO desalination processes are presented and discussed.

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Section: Coagulation-flocculationmentioning

confidence: 99%

Reverse osmosis desalination: A state-of-the-art review

et al. 2019

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“…Coagulants and colloids possess adverse electrical charges in water and thus when they meet the charges could be neutralized, resulting in fast aggregation of small-suspended particles to form microflocs (Liu, 2014). Generally, there are two types of coagulation, namely chemical coagulation (CC) and electrocoagulation (EC) (Harif et al, 2012;Lee and Gagnon, 2016). The CC process usually requires rapid and high energy mixing to ensure full mixing of coagulants to maximize formation of the microflocs (Koohestanian et al, 2008).…”

Section: Pretreatment Technologiesmentioning

confidence: 99%

A review of reverse osmosis membrane fouling and control strategies

Jiang

Li²

2017

Science of The Total Environment

753

362

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Reverse osmosis (RO) membrane technology is one of the most important technologies for water treatment. However, membrane fouling is an inevitable issue. Membrane fouling leads to higher operating pressure, flux decline, frequent chemical cleaning and shorter membrane life. This paper reviews membrane fouling types and fouling control strategies, with a focus on the latest developments. The fundamentals of fouling are discussed in detail, including biofouling, organic fouling, inorganic fouling and colloidal fouling. Furthermore, fouling mitigation technologies are also discussed comprehensively. Pretreatment is widely used in practice to reduce the burden for the following RO operation while real time monitoring of RO has the advantage and potential of providing support for effective and efficient cleaning. Surface modification could slow down membrane fouling by changing surface properties such as surface smoothness and hydrophilicity, while novel membrane materials and synthesis processes build a promising future for the next generation of RO membranes with big advancements in fouling resistance. Especially in this review paper, statistical analysis is conducted where appropriate to reveal the research interests in RO fouling and control.Graphic Abstract

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“…The suspension was filtered by a 0.45-μm fiber filter membrane. The pH of the filtered solution was adjusted to 7.5 using 0.1 mmol/L NaOH or HCl and the solution diluted to 1000 mL in a measuring flask (Lee and Gagnon 2016). The solution was stored in the dark.…”

Section: Suspensionmentioning

confidence: 99%

“…It is crucial to ensure maximum removal efficiency of suspended particles, because they can deteriorate water quality and destroy the supply and distribution system (Lee and Gagnon 2016). After chemical coagulant addition, precipitation begins immediately and initially to form very small particles which then lead to the formation of highly porous and irregularly shaped amorphous aggregates (He et al 2012;Wenzheng 2010).…”

Section: Introductionmentioning

confidence: 99%

Breakage and regrowth of flocs formed by sweep coagulation using additional coagulant of poly aluminium chloride and non-ionic polyacrylamide

Nan

Yao

Chen

et al. 2016

Environ Sci Pollut Res

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The breakage and regrowth of flocs formed by sweep flocculation were investigated on different flocculation mechanisms using additional dosage coagulant of poly aluminium chloride (PACl) and non-ionic polyacrylamide (PAM) to explore the reversibility after floc breakage. The optimal dosage of PACl was 0.15 mM (as alum), and zeta potential exceeding 1 mV meant that sweep flocculation was dominant in the pre-flocculated process. Re-coagulation efficiency increased with additional coagulants dosing, and sedimentation rates of flocs re-formed by small additional dosage of non-ionic PAM are faster than that of flocs re-formed by additional PACl. For additional inorganic coagulant (PACl) during regrowth processes, few negatively charged particles that existed in water sample restricted the effect of charge neutralization. An amorphous aluminum hydroxide precipitation could re-activate the weaker points on the broken floc surface, but regrown flocs have loose structure indicating worse settleability. For additional non-ionic PAM dosing, lower dosage showed large values of fractal dimension and average size, probably due to that unfolded curly molecular chain and exposed amide groups of non-ionic PAM which provide superb conditions for amide group interacting with particles. The use of non-ionic PAM in flocculation has advantage of being more effective than the cationic PACl, probably because it may avoid the re-stabilization of broken flocs by polymer adsorption driven by electrostatic attraction. Hence, appropriate dosing of PAM after breakage could improve the flocs characteristics with large size and compact structure.

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Comparing the growth and structure of flocs from electrocoagulation and chemical coagulation

Cited by 43 publications

References 24 publications

Reverse osmosis desalination: A state-of-the-art review

Reverse osmosis desalination: A state-of-the-art review

A review of reverse osmosis membrane fouling and control strategies

Breakage and regrowth of flocs formed by sweep coagulation using additional coagulant of poly aluminium chloride and non-ionic polyacrylamide

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