Is electrophoretic mobility determination meaningful for aluminum(III) coagulation of kaolinite suspension?

Xiao, Feng; Zhang, Xiangru; Lee, Cheryl

doi:10.1016/j.jcis.2008.08.023

Cited by 24 publications

(14 citation statements)

References 30 publications

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“…Coagulation studies have shown that both charge neutralisation and sweep coagulation including entrapment or bridge formation are the major coagulation mechanisms (Xiao et al (2008)). Of these, charge neutralisation is the most preferred economically and environmentally because it enables the coagulant dosage to be minimised and reduces the residual aluminium in water.…”

Section: Design Of Chemical Mixingmentioning

confidence: 99%

“…Rapid mixing (Cheremisinoff (2002), Asano et al (2007), Mavros (2001)), in water treatment is to rapidly disperse the coagulant into raw water, followed by flocculation (Ghernaout and Naceur (2011)), sedimentation (Goula et al (2008)), and filtration (Kurita (1999), De Zuane (1997), Xiao et al (2008)). This process has a strong influence on the overall treatment efficiency (O'connor et al important to make the metallic coagulants rapidly disperse into the whole fluid bulk.…”

Section: Introductionmentioning

confidence: 99%

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Review of Coagulation’s Rapid Mixing for NOM Removal

Ghernaout¹,

Boucherit²

2015

CHEM

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This review focuses on rapid mixing in the coagulation process for improved natural organic matter (NOM) removal in water treatment. Rapid mixing aims to instantly and efficiently disperse coagulant species into raw water, before flocculation, sedimentation, and filtration processes. Mechanical mixing with a longer retention time cannot guarantee an instantaneous and uniform coagulant dispersion. For this reason, the so-called pump diffusion mixer (PDM) has been proposed. Using various rapid mixing devices to test the sedimentation performance, it is showed that in-line hydraulic jet and static mixers are able to achieve performance equivalent to that of the mechanical mixing type at a lower coagulant dosage. On the other hand, the removal of NOM as disinfection by-products (DBPs) precursor by chemical coagulation (CC) has been extensively studied. It is well reported that enhanced coagulation (EC) by adjusting the pH downwards to 4-5 prior to coagulant addition will encourage the formation of soluble NOM-Al complex from low-turbidity waters. In case of most waters, therefore, acid must be added to maintain the desired coagulation pH for EC, and excess coagulant is required to improve the removal of NOM. However, CC using in-line hydraulic jet mixer such as PDM is a reasonable method for the improvement of coagulation process compared to EC, since it is possible to obtain good removals of NOM as well as turbidity using a lower dosages of coagulant without supplementary addition of chemicals for pH control and thus producing a smaller volume of waste solids.

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Section: Design Of Chemical Mixingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Review of Coagulation’s Rapid Mixing for NOM Removal

Ghernaout¹,

Boucherit²

2015

CHEM

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“…A generally accepted idea is that colloids will coagulate efficiently when the suspension electrophoretic mobility is near to zero, which is frequently achieved by dosing trivalent cations such as Fe(III) [52,53]. Concerning Fe(III) coagulation, however, Xiao et al [53] found that colloids were firstly enmeshed by voluminous ferric hydroxide precipitate or flocs, and the enmeshment of colloids by flocs was not dependent of the suspension electrophoretic mobility during Fe(III) coagulation.…”

Section: Indecisiveness Of Electrophoretic Mobility Determination Andmentioning

confidence: 99%

Controlling Coagulation Process: From Zeta Potential to Streaming Potential

Ghernaout¹

2015

AJEP

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This review concerns the using of Zeta and streaming potentials in the coagulation process control. Coagulation process is usually explained by charge neutralization mechanism. The negative charge may be quantified by Zeta potential or streaming potential measures. Prior to the advent of streaming current monitors, Zeta meters were the primary instruments for measuring electrokinetic properties as related to coagulant dose. Both instruments measure the potential and indirectly the particle surface charge, but use very different methods. Even if the on-line streaming current monitor can provide coagulation process optimization when properly installed, maintained, and interpreted, jar tests experiments and Zeta meters remain indispensable.

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“…Although zeta potential has been found indecisive in drinking-water flocculation using hydrolysable metal salts (Xiao et al 2008), the surface charge has long been believed to be important in controlling the stability of microbial aggregates. Bacteria may carry net negative surface charge when cultivated at physiological pH values.…”

Section: Effect Of Zeta Potential Of Free Cells On Biomass Flocculatimentioning

confidence: 99%

“…These properties may be characterized by zeta potential or surface charge, which is widely recognized as a vital factor governing the stability of bioaggregates and directly affects the sludge flocculability and settleability (Alibhai and Forstera 1986;Liao et al 2001;, although zeta potential has been found to be indecisive in drinking-water flocculation using hydrolysable metal salts (Xiao et al 2008). Surface hydrophobicity refers to the propensity of microbial cells being repelled from a mass of water and was shown to be an important factor that determined the relative bacterial adhesion and sludge compression potential (Olofsson et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Characteristics of free cells and aggregated flocs for the flocculation and sedimentation of activated sludge

2015

Int. J. Environ. Sci. Technol.

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Laboratory experiments were conducted to investigate the correlation of the free cells/aggregated flocs characteristics and the sludge flocculation and separation behavior during the activated sludge process. Activated sludge was cultured in three laboratory-scale batch reactors with same carbon sources of glucose but different sludge retention times (SRTs) of 5, 10 and 20 days. The variation in the operation condition produced sludge with different flocculation and separation characteristics. The reactor performance in terms of bioflocculation as measured by the amount of suspended solids in the effluent, sludge sedimentation and compression as measured by the sludge value index improved considerably as the SRT lengthened. The higher SRT was related to less negatively charged surface of free cells and more hydrophobic of aggregated flocs. The negative zeta potential of aggregated flocs (11-13 mV) was smaller than that of free cells (15-23 mV), and free cells carrying lesser negative surface charges resulted in effluent clarification. Hydrophobicity of aggregated flocs (10-17 %) in each reactor was higher than that of free cells (5-8 %). The increase in hydrophobicity of aggregated flocs had positive effect on settleability. Floc strength measured by breakage/erosion index was closely related to hydrophobicity of aggregated flocs, but no correlation could be established with zeta potential of aggregated flocs. In addition, different bacterial species existed in free cells and aggregated flocs. Microbial similarity between free cells and aggregated flocs increased with shorter SRT and was closely related to effluent clarification.

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Is electrophoretic mobility determination meaningful for aluminum(III) coagulation of kaolinite suspension?

Cited by 24 publications

References 30 publications

Review of Coagulation’s Rapid Mixing for NOM Removal

Review of Coagulation’s Rapid Mixing for NOM Removal

Controlling Coagulation Process: From Zeta Potential to Streaming Potential

Characteristics of free cells and aggregated flocs for the flocculation and sedimentation of activated sludge

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