Sweep Flocculation Research Articles

Mechanisms of nC60 removal by the alum coagulation–flocculation–sedimentation process

This study explored the mechanisms for nC60 removal in pure water and filtered saline wastewater by the alum coagulation–flocculation–sedimentation process through analyzing the hydrolyzed aluminum species and exploring the complexation of nC60 with aluminum hydroxide precipitates. Sweep flocculation (enmeshment and adsorption) with Alc is the most dominant mechanism contributing to the nC60 removal in pure water. In filtered saline wastewater, hetero-precipitation of Alb with nC60, colloids, and dissolved solids also contributes to the nC60 removal. Alkalinity affected the nC60 removal by changing the hydrolyzed aluminum species distributions. XPS, FTIR, and SEM evidences suggest that the enmeshment and adsorption of nC60 onto the aluminum hydroxide precipitates can be described as the inner-sphere complexation. Based on the above observations, conceptual models for nC60 removal by the alum coagulation–flocculation–sedimentation process in the different water matrices are proposed.

Flocculation kinetics and floc characteristics of dye wastewater by polyferric chloride–poly-epichlorohydrin–dimethylamine composite flocculant

The polyferric chloride–poly-epichlorohydrin–dimethylamine (PFC–ECH–DAM) composite flocculants with different OH/Fe ratios, Fe to organic ECH–DAM mass ratios and cross-linker types were comparatively investigated in terms of formed floc aggregation process and floc characteristics for the treatment of synthetic dyeing wastewater. The effect of OH/Fe molar ratio (B value), Fe to ECH–DAM mass ratio (MR value), cross-linker type and ECH–DAM addition on floc characteristics was investigated as function of flocculant dosage and dye wastewater pH. The results demonstrate that the synergic effect of PFC with ECH–DAM promoted the formation of larger flocs with higher growth rate and wider distribution of floc sizes. During the coagulation of reactive red (K-2BP) dyeing wastewater, strengthened floc properties can be obtained at higher flocculant dosage ranges (>80mg/L) and solution pH of about 7.5. The floc TWV values appear to show that the predominant flocculation mechanism of PFC–ECH–DAM are bridging adsorption and sweep flocculation. In addition, relatively lower OH/Fe molar ratio, higher Fe to ECH–DAM mass ratio and utilizing polyethylene polyamine as cross-linker were favorable for the formation of flocs with larger size, higher growth rate and larger size variation.

Return chemical sludge employed in enhancement of phosphate removal from wastewater

In this study, chemical sludge was recycled by using a coagulation process to improve phosphate removal from wastewater. A pilot experiment was conducted to investigate the appropriate ratio of recycled sludge, the appropriate operating conditions, and the mechanism involved in the enhancement of phosphate removal by return chemical sludge. The results showed that, with sludge recirculation, the process of coagulation for phosphate removal was enhanced by up to 12% compared with no sludge recirculation. Those effects were primarily attributed to the removal of relatively fine particles with a size of 100–310 μm. The sludge settleability was also improved by the addition of chemical sludge, which was mainly attributed to the increase in floc size. The appropriate ratio of recycled sludge was determined to be around 15–20%. Mixing and the aging time of recycled sludge had a significant effect on phosphate removal. Based on these findings, sweep flocculation and/or physical adsorption are expected to play key roles in enhancement of phosphate removal from wastewater.

Fouling of ultrafiltration membrane by algal-rich water: Effect of kalium, calcium, and aluminum

Algae are commonly aquatic plants showing generally negatively charged. The fouling behavior of hollow-fiber ultrafiltration membrane by algal-rich water could be therefore influenced by various cations (K+, Ca2+, and Al3+) and their doses. Microcystis aeruginosa solution was used as the feed solution to study the fouling in detail. Constant flux experiments were performed with a laboratory-scale experiment. Increasing the concentrations of calcium and aluminum had a significant impact on alleviating membrane fouling and increasing flux recovery by backwashing, especially for calcium. However, kalium ion had little influence on the membrane filtration. Based on the measurement of MW distribution and zeta potential, charge neutralization was proposed to be the primary aggregation mechanism for calcium, in contrast to precipitate coverage and sweep flocculation for aluminum. It was demonstrated that the fouling layer became more loose and porous in the presence of Ca2+ and Al3+, respectively, which can be identified by scanning electron microscope (SEM). However, SEM also proved that the two additives damaged the cell walls and caused the intercellular organic matter released to different extents.

Comparison of coagulation behaviour and floc characteristics of polyaluminium chloride (PAX 18, PAX XL19H, ALCAT) with surface water treatment

Abstract Coagulation behaviour of polyaluminium chloride (PACl) was comparatively investigated in terms of the removal of turbidity and colour with surface water. The growth of flocs was also compared. The results show that the decrease in saturation and values of dissolved oxygen was ca. 20% for ALCAT and PAX 18 at both dosages and 15% for PAX XL 19H, respectively. The floc formation growth indicated that PACl coagulation occurred not only by charge neutralization but also by a form of sweep flocculation. Besides, flocs formed by ALCAT had better sizes than the flocs formed by PAX 18 and PAX XL19H. The rate of sedimentation was stable during coagulation with higher doses, and it was dependent on the substance used.

Effect of Precipitant Additives on the Sludge Settling and Compacting Performance for Heavy Metal Wastewater Treatment

The purpose of this study is to investigate the impact of precipitant additives, i.e., calcium hydroxide (Ca(OH)2), calcium carbonate (CaCO3) and recycled sludge (RS), on the settling and compacting performance of sludge formed in the process of heavy metal wastewater treatment using bio-polymer ferric sulfate (BPFS). The results show that CaCO3 is the most suitable additive since heavy metal removal, sludge settling performance, and compacting performance is improved by 20%, 83.3%, 23.5%, respectively. In addition, scanning electron microscopy and X-ray diffraction were measured for contrasting the sludge morphology and crystallinity. The results suggest that CaCO3 acted as seeding material produces the largest flocs. Moreover, the flocculation theory combined with zeta potential measurement was used to explain the sludge formation mechanism, which is proposed as charge neutralization by BPFS, sweep flocculation by amorphous precipitate, and bridging flocculation by polyacrylamide (PAM) in sequence. The improvement of sludge properties by adding CaCO3 benefits from the enhancement of sweep flocculation. In summary, the interaction mechanism between precipitant additives and sludge performance is well understood, thus providing useful information about adding precipitant additives to improve both the sludge settling properties and the quality of the treated water during the heavy metal wastewater treatment.

Sweep Flocculation and Adsorption of Viruses on Aluminum Flocs during Electrochemical Treatment Prior to Surface Water Microfiltration

Bench-scale experiments were performed to evaluate virus control by an integrated electrochemical-microfiltration (MF) process from turbid (15 NTU) surface water containing moderate amounts of dissolved organic carbon (DOC, 5 mg C/L) and calcium hardness (50 mg/L as CaCO3). Higher reductions in MS2 bacteriophage concentrations were obtained by aluminum electrocoagulation and electroflotation compared with conventional aluminum sulfate coagulation. This was attributed to electrophoretic migration of viruses, which increased their concentrations in the microenvironment of the sacrificial anode where coagulant precursors are dissolved leading to better destabilization during electrolysis. In all cases, viruses were not inactivated implying measured reductions were solely due to their removal. Sweep flocculation was the primary virus destabilization mechanism. Direct evidence for virus enmeshment in flocs was provided by two independent methods: quantitative elution using beef extract at elevated pH and quantitating fluorescence from labeled viruses. Atomic force microscopy studies revealed a monotonically increasing adhesion force between viruses immobilized on AFM tips and floc surfaces with electrocoagulant dosage, which suggests secondary contributions to virus uptake on flocs from adsorption. Virus sorption mechanisms include charge neutralization and hydrophobic interactions with natural organic matter removed during coagulation. This also provided the basis for interpreting additional removal of viruses by the thick cake formed on the surface of the microfilter following electrocoagulation. Enhancements in virus removal as progressively more aluminum was electrolyzed therefore embodies contributions from (i) better encapsulation onto greater amounts of fresh Al(OH)3 precipitates, (ii) increased adsorption capacity associated with higher available coagulant surface area, (iii) greater virus-floc binding affinity due to effective charge neutralization and hydrophobic interactions, and/or (iv) additional removal by a dynamic membrane if a thick cake layer of flocs is deposited.

Impact of various coagulation technologies on membrane fouling in coagulation/ultrafiltration process

To evaluate the membrane fouling under traditional and enhanced coagulation, polyferric chloride (PFC) and polyferric chloride–polydiallyldimethylammonium chloride (PFC–PDMDACC) were applied in fulvic acid (FA)–kaolin treatment by a coagulation–flocculation/ultrafiltration process. Optimum dosages of PFC and PFC–PDMDAAC were ascertained in traditional and enhanced coagulation region by jar tests. Subsequently, the influences of the characteristics of flocs pre-formed in traditional and enhanced coagulation process on ultrafiltration (UF) membrane fouling were studied. The results of the study indicated that traditional coagulation, the first enhanced coagulation and the second enhanced coagulation occurred at the dosage of 15mg/L, 44mg/L and 72mg/L respectively in the PFC dosage range investigated in the experiments. And the coagulation mechanism was precipitation charge neutralization, charge neutralization, and sweep flocculation, respectively. For PFC–PDMDAAC, 10mg/L, 21mg/L and 41mg/L was the optimum dosage in traditional coagulation (charge neutralization), the first enhanced coagulation (bridging and charge neutralization) and the second enhanced coagulation (sweep flocculation) respectively. Flocs formed in traditional coagulation region were the biggest. The floc structure was the most compact in the first enhanced coagulation region. Flocs of the second enhanced coagulation region were highly positively charged and flocs of traditional coagulation region were positively charged for PFC and uncharged for PFC–PDMDAAC. For both PFC and PFC–PDMDAAC, the hierarchy of membrane fouling under traditional and enhanced coagulation was traditional coagulation>the first enhanced coagulation>the second enhanced coagulation. Enhanced coagulation could reduce the UF membrane fouling effectively.

Effects of Slow-Mixing on the Coagulation Performance of Polyaluminum Chloride (PACI)

Conventional jar tests and on-line size monitoring were used to investigate the effects of slow-mixing intensity and duration on residual turbidity and floc size during charge neutralization coagulation and sweep flocculation with polyaluminum chloride. The compensatory effect of slow-mixing on coagulation performance following inadequate or excessive rapid-mixing was also examined. It is found that slow-mixing intensity has a more marked positive effect on charge neutralization coagulation than on sweep flocculation. The optimal root-mean-square velocity gradient, G, for slow-mixing is 15 s−1 for both coagulation mechanisms, and charge neutralization coagulation requires a longer slow-mixing duration. The optimal slow-mixing duration, based on residual turbidity, is longer than the time to form the largest mean flocs. The optimal product of G and mixing duration, GT, for slow-mixing during charge neutralization coagulation (13500) are higher than that during sweep flocculation (4500) and both are less than the range of values recommended by the American Water Works Association (24000-84000). The optimal GT value under various slow-mixing conditions increases with G. Appropriate extension of slow-mixing duration during charge neutralization coagulation can improve coagulation performance after an inadequate or excessive rapid-mixing duration, but during sweep flocculation, appropriate shortening of slow-mixing duration after an excessive rapid-mixing or appropriate extension of slow-mixing duration after an inadequate rapid-mixing is favorable.

Efficient microalgae harvesting by organo-building blocks of nanoclays

The synthesis of aminoclays with Mg2+ or Fe3+, placed in metal centers by sol–gel reaction with 3-aminopropyltriethoxysilane (APTES) as a precursor, is demonstrated, producing –(CH2)3NH2 organo-functional pendants which are covalent-bonding onto cationic metals. The protonated amine groups in aqueous solution lead the efficient sedimentation (harvesting) of microalgae biomass within approximately 5 min and 120 min for fresh and marine species, respectively. To our surprise, the aminoclays did not depend on microalgae species or media for microalgae harvesting. In particular, the harvesting efficiency (%) of microalgae was not decreased in a wide pH region. The harvesting mechanism can be explained by the sweep flocculation of microalgae, which is confirmed by measurement of zeta potential of aminoclay in aqueous solution where aminoclay shows a positively charged surface in a wide pH region. In order to reduce the cost of aminoclays and to make the harvesting procedures simple, the membrane process using aminoclay-coated cotton filter is introduced for the treatment of 1 L-scale microalgae stocks. It is successfully performed with three recycles using the same aminoclay-coated cotton filter after removing the harvested microalgae biomass. Conclusively, the aminoclay-based microalgae harvesting systems are a promising means of reducing the cost of downstream processes in microalgae-based biorefinery.

Effect of coagulation mechanisms on the fouling and ultrasonic cleaning of PTFE membrane

In this study, the effect of coagulation pretreatment on membrane fouling and ultrasonic cleaning efficiency was investigated using a dead-end polytetrafluoroethylene (PTFE) microfiltration system. The extent of membrane fouling was examined under different coagulation mechanisms such as charge neutralization (CN), electrostatic patch effect (EPE) and sweep flocculation (SW). Fouling through EPE mechanism provided the greatest flux decline and least permeate flux recovery over CN and SW. EPE produces more stable, smaller and more compact flocs while CN and SW have large, easily degraded and highly-branched structured flocs. The predominant fouling mechanism of EPE, CN and SW is pore blocking, a combination of pore blocking and cake formation, and cake formation, respectively. Better permeate flux recovery is observed with SW over CN and EPE, which implies formation of less dense and more porous cake deposits. The morphology of fouled membranes was examined using scanning electron microscopy (SEM).

Optimization of electrocoagulation process for removal of an azo dye using response surface methodology and investigation on the occurrence of destructive side reactions

The optimization and modeling of the electrocoagulation process which conducted by means of iron (EC-Fe) and aluminum (EC-Al) anodes, in the removal of C.I. Reactive Red 43 were performed through the response surface methodology (RSM). Moreover, the occurrence of possible destructive reactions during both EC-Fe and EC-Al processes was investigated using UV–Vis spectrometry, total organic carbon (TOC) and GC–MS analyses. The electrocoagulation experiments were carried out in a monopolar batch reactor using two anodes and two cathodes in parallel connections. Current density, time, pH and chloride concentration were considered as input variables for RSM. The analysis of variance revealed a high coefficient of determination (REC-Fe2=0.981 and REC-Al2=0.934) between experimental removal efficiency and predicted one by RSM developed models. The optimum conditions proposed by RSM to reach the maximum RR43 removal through the EC-Fe were different from the ones proposed for the EC-Al. At the optimum conditions, the removal efficiency of dye was more than 99% for both processes, whereas 90.58% and 98.37% of initial TOC concentration decreased during EC-Fe and EC-Al processes, respectively. The analyses results confirmed that beside sweep flocculation mechanism, known as the main removal mechanism, the degradation of dye was occurred during EC-Fe as a minor pathway.

Aggregation of nano-sized alum–humic primary particles

In order to understand the mechanism of floc formation and growth in coagulation process, effect of zeta potential and surface characteristic of nano sized primary particles on coagulation efficiency were investigated by coagulation of humic acid with alum in this study. It was demonstrated that only 1min rapid mixing was enough for adsorption of humic acid onto the precipitates of alum, and 15min flocculation (slow mixing) only induced the formation and growth of flocs. The primary particle size of alum–humic flocs was near 50nm and spherical. Mathematical model deduced from Derjaguin–Landau–Verwey–Overbeek (DLVO) theory showed that the formation of micro-flocs (or lag time) was determined by the square value of zeta potential of nano-sized primary particles and intensity of Brownian motion, which is closely related to water temperature. There was an absolute critical zeta potential, i.e. 13.5mV in this study, determining whether two nano-sized particles could overcome the energy barrier consisted of Van der Waals force and electrical double layer repulsion force to allow floc formation to occur at a certain temperature. The Brownian motion determined whether the nano-sized primary particles (aluminum hydroxide precipitates with humic acid) had the opportunity to overcome the repulsive force and cement with each other. Low coagulation efficiency at high latitude area in winter is caused by low collision frequency, which is mainly attributed to the low intensity of Brownian motion at a low temperature. Furthermore, it was demonstrated that aggregation of micro-flocs or their clusters significantly depended on activated sites on the primary particles rather than the zeta potential of primary particles when sweep flocculation dominated the coagulation mechanism if the size of flocs was larger than some value.

Sweep flocculation as a second form of charge neutralisation—a review

Abstract The coagulation/flocculation (C/F) processes are mainly due to charge neutralisation (CN) and sweep flocculation (SF) mechanisms. However, the SF mechanism has also its CN property moreover than its well-known weighting characteristic. On this weighting characteristic, the literature has usually focused without taking in consideration the SF’s CN property. This review discusses the implicated mechanisms in destabilisation of colloids and aggregation of flocs. Colloids are very small particles that have extremely large surface area. The consequence of this smallness in size and mass and largeness in surface area is that in colloidal suspensions: gravitational effects are negligible and surface phenomena predominate. Hence, during C/F process, colloids are removed by CN and SF mechanisms which act on the anionic charge of the colloid by its neutralisation prior to its removal by sedimentation/filtration. The sweep flocs can be described as large aggregates of Al(OH)3/Fe(OH)3 that are formed when Al...

Activity and stability of different immobilized preparations of recombinant E. coli cells containing ω-transaminase

Production of chiral amines using ω-transaminases has been thoroughly studied in recent years. Immobilized ω-transaminases, however, have been used on relatively few occasions despite potential benefits such as reuse of enzyme and ease of product purification. In this study principally different methods including surface immobilization, entrapment and sweep flocculation using titanium oxide, Ca-alginate and chitosan respectively were evaluated for the immobilization of recombinant Escherichia coli cells. The enzyme expressed was a modified Arthrobacter citreus ω-transaminase with improved thermostability. The preparations were compared in terms of cell loading capacity, operational stability in repeated batches and storage stability using the conversion of methylbenzylamine to acetophenone.The use of chitosan for cell immobilization proved to be the method of choice since it was both very simple and effective. At a very high cell loading of 3.2g cells/g chitosan >60% activity was observed. The preparation was reused in eight successive 1-h batches with >90% remaining activity. To further demonstrate its usability the preparation was used for asymmetric synthesis of (S)-4′-cyano-(α)-methylbenzylamine in three repeated bathes (cycle time >20h), using isopropylamine as the amine donor. Storage stability was comparable with that of non-immobilized cells. It was concluded that the chitosan method due to its properties and simplicity would be advantageous for use also on a larger scale.

Mechanisms of virus control during iron electrocoagulation – Microfiltration of surface water

Results from a laboratory-scale study evaluating virus control by a hybrid iron electrocoagulation – microfiltration process revealed only 1.0–1.5 log MS2 bacteriophage reduction even at relatively high iron dosages (∼13 mg/L as Fe) for natural surface water containing moderate natural organic matter (NOM) concentrations (4.5 mg/L dissolved organic carbon, DOC). In contrast, much greater reductions were measured (6.5-log at pH 6.4 and 4-log at pH 7.5) at similar iron dosages for synthetic water that was devoid of NOM. Quantitative agreement with Faraday’s law with 2-electron transfer and speciation with phenanthroline demonstrated electrochemical generation of soluble ferrous iron. Near quantitative extraction of viruses by dissolving flocs formed in synthetic water provided direct evidence of their removal by sorption and enmeshment onto iron hydroxide flocs. In contrast, only approximately 1% of the viruses were associated with the flocs formed in natural water consistent with the measured poor removals. 1–2 logs of virus inactivation were also observed in the electrochemical cell for synthetic water (no NOM) but not for surface water (4.5 mg/L DOC). Sweep flocculation was the dominant destabilization mechanism since the ζ potential did not reach zero even when 6-log virus reductions were achieved. Charge neutralization only played a secondary role since ζ potential → 0 with increasing iron electrocoagulant dosage. Importantly, virus removal from synthetic water decreased when Suwanee River Humic Acid was added. Therefore, NOM present in natural waters appears to reduce the effectiveness of iron electrocoagulation pretreatment to microfiltration for virus control by complexing ferrous ions. This inhibits (i) Fe2+ oxidation, precipitation, and virus destabilization and (ii) virus inactivation through reactive oxygen species intermediates or by direct interactions with Fe2+ ions.

モデルコロイドの凝集沈降実験に基づく天然粘土鉱物イモゴライトの濁水凝集機構

Flocculants made of natural volcanic ash soils can be used to purify turbid water in reservoirs. Imogolites in the flocculants seem to play an important role when the flocculants are applied. To clarify the mechanism of imogolite-induced flocculation, we studied the flocculation and charging of latex particles as a function of the ratio of the concentration of imogolites (CI) to that of latex particles (CL) at three different pH. The mechanisms at each pH are found as follows. At pH4, flocculation occurs only around CI/CL=0.01, where the particles are uncharged found from electrophoretic mobility. Thus, the mechanism at pH4 is charge neutralization. At pH6.5, the suspensions flocculate when CI/CL is higher than 0.01; the particles flocculate due to charge neutralization as well as sweep flocculation, by which latex particles are enmeshed by the flocs of imogolites. At pH10, where imogolites and latex particles bear negative charge, the suspensions flocculate when CI/CL exceeds 0.1. Only the sweep flocculation acts at pH 10.

Characterization of Al-Humic Complexation and Coagulation Mechanism

Using fluorescence and optical monitoring techniques, the process of coagulation of natural humic acids (HA) was studied paying attention to the interaction of aluminium and HA. Experiments were conducted using a jar tester equipped with a PDA2000 monitoring device for online monitoring of the Al-humic coagulation process. After flash mixing, slow mixing and settling, the supernatant was collected for fluorescence analysis to measure the concentration of residual aluminium which has not reacted with HA molecules. The process of aluminium hydrolysis was also studied by online monitoring of the formation of ‘alum flocs’ in a solution free from HA. Electrophoretic analysis and TOC measurement were conducted respectively for evaluating the condition of charge neutralization and HA removal. On this basis, the mechanism of Al-humic coagulation was discussed. It can be concluded that at pH 5, charge-neutralization and co-precipitation is the main mechanisms of coagulation, while at pH 7 the main hydrolyzed species are precipitated aluminum hydroxides so that sweep flocculation becomes the main mechanism of coagulation as well as overdosing at pH 5.0.

Aluminum electrocoagulation pretreatment reduces fouling during surface water microfiltration

A bench-scale study was undertaken to evaluate aluminum electrocoagulation pretreatment for dead-end, constant pressure microfiltration of surface water. Electrochemical aluminum production quantitatively obeyed Faraday's law with a 3-electron transfer at nearly 100% efficiency resulting in Al(OH) 3 precipitation. X-ray diffractometry proved that Al(OH) 3 precipitates were predominantly amorphous. Enmeshment of colloids in amorphous precipitates (sweep flocculation) was the predominant colloid destabilization mechanism. Additionally, the floc zeta potential became less negative (→0) as more and more aluminum was added indicating the secondary role of adsorption of hydrolyzed aluminum species and charge neutralization in destabilization. Fouling of a commercially available polymeric microfiltration membrane following electrocoagulation pretreatment was found to (i) be lower at pH 6.4 compared with 7.5, (ii) decrease only up to an intermediate aluminum dosage, and (iii) exacerbate with increasing transmembrane pressure. In all experiments, cake filtration was the predominant flux decline mechanism for the entire duration of microfiltration. Increased fouling at higher transmembrane pressures (manifested as more rapid decline of the instantaneous flux normalized by the initial flux) was attributed to cake compressibility. Optical microscopy revealed that floc sizes increased monotonically with aluminum dosage even though fouling worsened at high electrocoagulant concentrations. This suggests that fouling was controlled by antagonistic effects of adding more and more aluminum coagulant; increasing total mass loading of colloidal foulants (higher total filtration resistance) and creating larger flocs (decreasing specific cake resistance). Significant reductions in microfilter fouling with aluminum electrocoagulation pretreatment suggests the next logical step of larger-scale testing under “real-world” conditions before recommending it for surface water treatment.

Fouling Elimination of PTFE Membrane under Precoagulation Process Combined with Ultrasound Irradiation

Precoagulation is one of the effective pretreatments in membrane filtration. This process mitigates membrane fouling, which is the major drawback of membrane technology in drinking water and wastewater treatment. This study investigated the effects of precoagulation under different coagulation mechanisms on membrane fouling. Use of ultrasound in polytetrafluoroethylene (PTFE) membrane cleaning was also evaluated. In precoagulation, synthetic raw water was precoagulated using aluminum sulfate at different coagulation mechanisms, named electrostatic patch effect (EPE), charge neutralization (CN), and sweep flocculation (SW). Flocs produced from different coagulation mechanisms exhibited different sizes, structures, and strengths. Likewise, the fouling type generated from each mechanism was demonstrated as pore blocking for EPE, cake formation for SW, and combination phenomenon for CN. Moreover, this study indicated that the membrane flux was enhanced in the sequence of EPE>CN>SW. The flux recovery rate after ultrasonic cleaning was in the sequence of SW>CN>EPE. Finally, this study evidenced that the floc characteristics from various coagulation mechanisms affected membrane performance, fouling types, and ultrasonic cleaning efficiency.