Floc Morphology Research Articles

What occurs in colloidal gas aphron-induced separation of titanium dioxide nanoparticles? Particle fate analysis by tracking technologies.

As an important method of enriching, separating and removing nanoparticles, colloidal gas aphrons (CGAs) need to be investigated for the fate and interfacial behaviors of particles during the process. It is beneficial to sufficiently interpreting the process performance and mechanisms. This study employed complementary tracking technologies to analyze the extensively-used engineered nanoparticles - TiO2 nanoparticles (TiO2-NPs) in effluent and floats of CGA process. Results denote that, at the optimum SDS relative dosage of 0.78mg/mg TiO2, the particle number concentration was largely reduced by 2-4 orders of magnitude based on nanoparticle tracking analysis (NTA) whilst approximately 84.0% of TiO2-NPs were separated according to inductively coupled plasma-mass spectrometry (ICP-MS). NTA shows the change of overall particle dispersion status in the water phase while ICP-MS provides the Ti-related separation effect. Particularly, the particle size variation for the scenario of overdosing CGAs was clearly observed by NTA. Micro-Raman, dynamic laser scattering and small angle laser light scattering exhibited advantages in obtaining the configuration and morphology of flocs. The large flocs with open structure were apt to form and be favorably separated at the appropriate CGA dosage. However, overdosing CGAs weakened the capture capacity of bubbles and gave rise to small and dense aggregates. This work, for the first time, shows the change of nanoparticles in water and solid phases using the important and novel nanoparticle collection method - CGA technology. It also provides a reference to other flotation-related technologies for studying the nanoparticle fate and the process performance.

Fit-for-purpose treatment of produced water with iron and polymeric coagulant for reuse in hydraulic fracturing: Temperature effects on aggregation and high-rate sedimentation

Reusing produced water for hydraulic fracturing simultaneously satisfies challenges of fresh water sourcing and the installation/operation of an extensive disposal well infrastructure. Herein, we systematically and rigorously investigate produced water treatment for reuse during hydraulic fracturing. Highly saline and turbid produced water from the Permian Basin was treated by adding chlorine as an oxidant, FeCl3 as the primary coagulant, and an anionic polymer to induce high rate sedimentation to generate “clean brine” by removing suspended solids and iron over a range of environmentally relevant temperatures. Mobile phone video capture, optical microscopy, and digital image/video analysis were employed to characterize floc morphology and measure its size and settling velocity. Conformational changes of the polymeric coagulant between 4 and 44 °C were inferred from viscosity and dynamic light scattering measurements providing clues to its performance characteristics. Floc settling velocities measured over the entire range of polymer dosages and temperatures were empirically modelled incorporating their fractal nature, average size, and the viscosity of the produced water using only a single fitting parameter. Juxtaposing the anionic polymer with the hydrolyzing metal-ion coagulant effectively destabilized the suspension and caused floc growth through a combination of enmeshment, adsorption and charge neutralization and inter-particle bridging as evidenced by Fourier transform infrared spectroscopy and thermogravimetric analysis. Very high turbidity (≥98%) and total iron (≥97%) removals were accomplished even with very short flocculation and sedimentation times of only 6 minutes each suggesting the feasibility of this approach to reuse produced water for hydraulic fracturing.

Experimental investigation and mathematical modeling of the competition among the fast-growing “r-strategists” and the slow-growing “K-strategists” ammonium-oxidizing bacteria and nitrite-oxidizing bacteria in nitrification

Based on their differences in the kinetic values, the nitrifiers could be classified into the fast-growing “r-strategists” and the slow-growing “K-strategists” bacteria. However, the difference in the kinetic values originated not only from the intrinsic differences among the nitrifier species, but also from other factors, i.e. sludge floc morphology, and the environment in which the nitrifiers were cultivated. It is not clear how these factors interact and affect the measured kinetic parameters and the competition among the “r-strategists” and the “K-strategists” bacteria. In this study, the kinetic parameters of nitrifiers cultivated in the SBR (sequencing batch reactor) under different substrate concentrations were monitored, together with the identification of nitrifier species and sludge floc morphology characterization. The results showed that the r-AOB and r-NOB (“r-strategists” ammonium-oxidizing bacteria and nitrite-oxidizing bacteria, i.e., Nitrosomonas and Nitrospira) were the dominant nitrifiers in the SBR reactor. A mathematical model describing the competition between r/K AOB and NOB showed that r-AOB and r-NOB could be enriched in the SBR. The experimental investigation supported the model simulation results. The model simulation also revealed that the different r/K AOB and NOB species could be enriched in different DO concentrations and SRT conditions, which could be manipulated to promote the growth of r-AOB and NO2− accumulation for the autotrophic nitrogen removal using ANAMMX.

Establishment of the Permeability Model for Soft Solid Sludge Conditioned with Flocculants.

Permeability plays a decisive role in the dewatering process and reflects the difficulty of filtration, especially for soft solid material such as sludge. In this paper, the physicochemical properties and dewatering performance of sludge conditioned with different kinds of flocculants were investigated. Results showed that the flocculant could change the sludge microstructure such as floc morphology, specific surface area, and fractal dimension. Compared with filtration pressure, flocculants had a greater influence on sludge permeability which was a significant negative correlation with filtration pressure and was a positive correlation with flocculant dosage. In order to describe the fact that fluid flows through the porous voids for soft solid sludge, the improved Kozeny constant was corrected. Research showed that permeability was more significant in the dewatering process for the sludge conditioned with inorganic flocculants than that with organic flocculants. The Kozeny constant was not only relevant with suspension nature but also with filtration pressure. The range of the improved Kozeny constant was reasonably determined based on flocculant type, concentration, and filtration pressure, which was of great help to project applications. For raw sludge, the improved Kozeny constant was 958 times than that of the original value, and it decreased significantly for conditioned sludge.

Optimizing sludge dewatering with a combined conditioner of Fenton's reagent and cationic surfactant

Enhancing sludge dewatering is of importance in reducing environmental burden and disposal costs. In this work, a cationic surfactant, cetyl trimethyl ammonium bromide (CTAB), was combined with Fenton's reagent for sludge dewatering. Results show that the Fenton-CTAB conditioning significantly promotes the sludge dewatering. Using combined techniques of response surface methodology and uniform design, dosages of Fe2+, H2O2, and CTAB for water content response were optimized to be 89, 276, and 233 mg/g dry solids (DS), respectively. The water content of sludge decreased from 79.0% to 66.8% under the optimal conditions. Compared with cationic polyacrylamide, the Fenton-CTAB system exhibited superior sludge dewatering performance. To gain insights into the mechanisms involved in sludge dewatering, the effects of Fenton-CTAB conditioning on the composition of extracellular polymeric substances (EPS) and the morphology of the sludge flocs were investigated. The decomposition of EPS into some dissolved organics and the release of proteins in tightly bound EPS facilitated the conversion of bound water to free water and further reduced the water content of sludge cake. After conditioning, morphology of sludge showed aggregation. Overall, the enhanced sludge dewatering by Fenton-CTAB treatment provides an efficient way for management of sewage sludge.

A significant improvement of fine scheelite flotation through rheological control of flotation pulp by using garnet

The paper proposes a novel method which utilizes the garnet to realize the rheological control of the flotation pulp in fine scheelite flotation. The garnet was added in the conditioning operation of the cleaning flotation stage. Sodium oleate and water glass were used as flotation collector and depressant, respectively. Flotation tests on the cleaning flotation with different addition of garnet were conducted, coupled with rheological measurements, flotation rate calculation and optical observations on the corresponding flotation pulp and froth. It is found that there exists strong correlation among the flotation rate, pulp rheology, froth and floc morphology in the cleaning flotation. As the garnet content in the cleaning flotation pulp increases, the viscosity of the flotation pulp decreases and the flotation rate increases; the floc morphology changes from big-branch type to globule-like and the flotation froth becomes cleaner. It is also found that the changes in the fluid properties of the flotation slurry caused by the garnet addition are closely related to the flotation selectivity. As the slurry yield stress decreases and the flotation slurry deviates nearer to the Bingham fluid, the flotation rate increases and the flotation selectivity improves. The results could potentially be used to improve the flotation performance of fine scheelite ore through rheological control of flotation pulp by garnet addition in cleaning flotation operations.

Variations of physical and chemical properties in relation to erythromycin mycelial dreg dewaterability under heat-activated persulfate oxidation conditioning

Erythromycin mycelial dreg (EMD) resulting from erythromycin (ERY) production process may be used as a nutrient resource. However, it has a high moisture content, which makes handling operations complicated. In this study, the EMD dewaterability under heat-activated persulfate (PS) oxidation conditioning was investigated. The variations of physical and chemical properties of EMD were further investigated to uncover the underlying mechanism of EMD dewaterability. Results indicated that EMD dewaterability was worse under single heat process, but significantly improved under heat-activated PS oxidation process. Heat-activated PS oxidation conditioning was capable to increase zeta potential, reduce median particle size, alter EMD flocs morphology, and disrupt mycelial cells. Concurrently, heat-activated PS oxidation conditioning resulted in the decrease of protein in tightly bound (TB) extracellular polymeric substances (EPS) and total EPS, and the decrease of fluorescing constituents (tryptophan protein, tyrosine protein and tryptophan amino acid) in EPS. Furthermore, a possible mechanism was proposed for heat-activated PS oxidation conditioning.

Microalgae harvesting with the novel flocculant hairy cationic nanocrystalline cellulose.

This paper investigates the flocculation of Chlorella sorokiniana suspensions with a novel cellulose derivative, namely hairy cationic nanocrystalline cellulose (CNCC). CNCC are a brand new family of nanocellulose characterized by having two positively charged amorphous ends joint through a common crystalline shaft. Flocculation was monitored through laser reflectance and its mechanism was studied by means of zeta potential, fractal dimension and turbidity removal. CNCC dosage and shear rate were varied and their effect on floc morphology and filterability were assessed. CNCC effectively flocculated the cultures at dosages well below and over the isoelectric point, being the flocculation mechanisms and floc strength highly dependent on the doses applied. The filtration propensity of flocculated suspensions proved highly sensitive to small differences in flocs' geometry. The aggregation process entailed two phases, a first one in which the CNCC adsorbed on the surface of microalgal cells according to a flat random deposition up to reaching a maximal cell coverage, and a second one in which the free spots left were progressively covered with orthogonally deposited CNCC, being this later configuration the main responsible for intercellular attachment. The present work demonstrates that CNCC is an effective flocculant of microalgal cell suspensions and constitutes an alternative worth exploring for the aggregation of other cells' suspensions.

Effects of Mixing Conditions on Floc Properties in Magnesium Hydroxide Continuous Coagulation Process

Magnesium hydroxide continuous coagulation process was used for treating simulated reactive orange wastewater in this study. Effects of mixing conditions and retention time on the coagulation performance and floc properties of magnesium hydroxide were based on the floc size distribution (FSD), zeta potential, and floc morphology analysis. Floc formation and growth in different reactors were also discussed. The results showed that increasing rapid mixing speed led to a decrease in the final floc size. The floc formation process was mainly carried out in a rapid mixer; a rapid mixing speed of 300 rpm was chosen according to zeta potential and removal efficiency. Reducing retention time caused a relatively small floc size in all reactors. When influent flow was 30 L/h (retention time of 2 min in rapid mixer), the average floc size reached 8.06 μm in a rapid mixer; through breakage and re-growth, the floc size remained stable in the flocculation basin. After growth, the final floc size reached 11.21 μm in a sedimentation tank. The removal efficiency of reactive orange is 89% in the magnesium hydroxide coagulation process.

The influence of particle size and concentration combined with pH on coagulation mechanisms

In order to evaluate the influence of particle size and particle concentration on the coagulation process, two kinds of particle suspensions, nanoparticles and microparticles, were employed to investigate the effect of particle size on coagulation mechanisms with varying coagulation parameters. Results showed that it is easier for nanoparticles to cause self-aggregation because of Brownian motion, while interception and sedimentation are the mainly physical processes affecting particle transport for microparticles, so they are more stable and disperse more easily. The particle size distribution and particle concentration had distinct influence on the coagulation mechanisms. Under neutral conditions, as the amount of coagulant increased, the coagulation mechanism for nanoparticles changed from charge neutralization to sweep flocculation and the nanoparticles became destabilized, re-stabilized and again destabilized. For microparticles, although the coagulation mechanism was the same as that of nanoparticles, the increased rate of aluminum hydroxide precipitation exceeded the adsorption of incipiently formed soluble alum species, resulting in the disappearance of the re-stabilization zone. Under acidic conditions, Brownian motion dominates for nanoparticles at low particle concentrations, while sweep flocculation is predominant at high particle concentrations. As for microparticles, charge neutralization and sweep flocculation are the mechanisms for low and high particle concentrations respectively. Under alkaline condition, although the mechanisms for both nano- and microparticles are the same, the morphology of flocs and the kinetics of floc formation are different. At low particle concentrations, nanoparticles have larger growth rate and final size of flocs, while at high particle concentrations, nanoparticles have higher fractal dimension and recovery factors.

Enhanced coagulation by high-frequency ultrasound in Microcystis aeruginosa-laden water: Strategies and mechanisms

Ultrasonic treatment has attracted much attention because of its physical and chemical effects that are distinct from those of chemical agents. In particularly, high-frequency ultrasound is known as an effective method because the theoretical resonance frequency of the gas vesicles in Microcystis aeruginosa is in the high frequency range (>100 kHz), which causes gas vesicles collapse and changes the settleability of the algal cells. In this work, the effects of the ultrasonic frequency, acoustic power density and duration on enhancing coagulation to remove turbidity in algae-laden water were studied. In order to explain the mechanism, the morphology of algae cells, the changes in extracellular organic substances, the zeta potential and the formation of hydroxyl radicals were analyzed systematically. Finally, Zeta potentials and flocs morphology after adding PAC were investigated to verify the mechanism. The results showed that the frequency exhibited fewer effects than power and duration on coagulation. SEM images showed that there were more severe cellular damages at 430 and 740 kHz than other frequencies. Sonication could cause the collapse of gas vesicle inside the cell, which was due to the instantaneous high pressure generated by the ultrasonic cavitation instead of the resonance. Furthermore, sonication would result in an increase in proteins in extracellular organic matter (EOM) with continuous ultrasonic irradiation, indicating that a small amount of proteins could promote coagulation and that the accumulation of proteins would inhibit coagulation. Free radical content testing showed that the production of excessive free radicals was often accompanied by a deterioration of the coagulation. The proper mechanical effects were the main mechanism of ultrasonic enhanced coagulation. Thus, it was recommended that the appropriate ultrasonic condition was the one that resulted in a small amount of protein leakage and little generation of free radicals, which occurred at 740 kHz and 0.02 W/mL in approximately 5 min, and would significantly enhance the turbidity removal rate in algae-containing water from approximately 80–90%.

Improvement of activated sludge dewatering properties using green conditioners: chitosan hydrochloride and lysozyme.

In this study, the effects of chitosan hydrochloride (CTSCL), lysozyme (LZM) and cationic polyacrylamide (CPAM) as conditioners on the dewatering performance of activated sludge were comparatively investigated in terms of the capillary suction time (CST), specific resistance to filtration (SRF) and water content after conditioning and subsequent dewatering. CTSCL showed nearly the same capacity to improve the sludge dewaterability as CPAM, with CTSCL and CPAM conditioning resulting in the SRF of sludge decreasing by 95.82% and 96.15%, CST decreasing by 78.22% and 84.88%, and water content of the dewatered sludge decreasing by 10.84% and 8.5%, respectively. However, LZM conditioning exhibited the best improvement in the dewatering extent, which could decrease the water content of dewatered sludge by 19.84%. In addition, the evolution of the physical properties, extracellular polymeric substance content and composition, and the sludge floc morphology were analyzed to explain the sludge conditioning mechanism. Both CTSCL and CPAM could extrude sludge surface bound water into free water, produce sludge flocs with a larger size and more surface pores and finally improve the sludge filterability. In comparison with chemical flocculants, the conditioning mechanism of LZM was distinctly different, which effectively decomposed cell walls, released the internal bound water beneficial for improving the sludge dewatering extent, while the released organic substances clogged the floc surface, and the high proportion of fine particles in the flocs resulted in poorer filtration.

Effects of acid-heat combined treatment on sludge dewatering performance at low temperature

The effects of different initial pH value, temperature and heating time on sludge dewatering performance were studied by treating sludge with acid-heat combination at low temperature and taking dewatering rate (amount of filtrate per unit time) and dewatering degree (moisture content of mud cake) as indexes to evaluate the sludge dewatering performance. And the mechanism of action was preliminarily discussed by analyzing the concentration of SCOD, protein and polysaccharide in sludge supernatant, Zeta potential and floc morphology of sludge. The results showed that the concentration of organic matter in sludge supernatant increased significantly when the sludge was treated by acid-heat combination, which indicated that the method promoted the fragmentation and dissolution of sludge flocs, and the internal bound water was released more, at the same time, the decrease of Zeta potential and the increase of temperature were beneficial to the flocculation of sludge, which effectively improved the degree and rate of sludge dewatering. The optimal conditioning conditions were determined as follows: pH 3, temperature 90°C and heating time 40 min. Under such condition, the sludge dewatering rate reached 21.30 ml/min and the moisture content of mud cake decreased to 63.20%.

Study on activated sludge flocs morphology and composition in a full-scale wastewater treatment plant in Poland

Study on activated sludge flocs morphology and composition in a full-scale wastewater treatment plant in Poland

Rapid and efficient activated sludge treatment by electro-Fenton oxidation

Advanced oxidation process is one of the important process to improve the efficiency of activated sludge dewatering and digestion. In this study, electro-Fenton (EF) was investigated as a pretreatment method for improving activated sludge dewatering and disintegration in terms of specific resistance to filtration, volatile suspended solids removal and release of soluble organics. The morphology of sludge flocs and properties of extracellular polymeric substance (EPS) were investigated to understand the involved mechanisms. The results showed that EF could increase the dewaterability of activated sludge effectively in 40–60 min. The size of sludge flocs decreased after EF treatment, but zeta potential was elevated to near zero and floc structure became coarser with bigger holes. EF could enhance the sludge floc disintegration, released protein and polysaccharide to soluble EPS fraction, and promote the humification process. The kinetic analysis further indicated that EF increased the pseudo first-order EPS solubilization rate. EF had high operational stability by retaining over 90% initial activity even after five repeated use of dewatering filtrate. This study provides a rapid and efficient solution for improving sludge dewaterability by electro-Fenton.

Effect of impeller clearance on floc growth behaviors in a baffled square stirred-tank reactor: Flocculation-test and CFD-aided studies

The impeller clearance (C) and shear rate (Gave) effects on aggregation and breakage behaviors in the whole process of floc growth were investigated by applying lab-scale flocculation tests with the aid of computational fluid dynamics (CFD) simulations. For a baffled square stirred-tank flocculating reactor, the recirculating times for water flow to the impeller region and intensity of turbulence occurring within this region, together with the non-uniform nature of turbulence for water flow above the rotating impeller, were found to be more or less different in all C-value cases at a constant Gave, thereby affecting the development of floc morphology. Besides, the importance of impeller clearance (C) to floc morphological evolution seemed to be largely determined by predominant growth behavior(s), likely as a result of distinct occurring degrees of either aggregation or breakage for each combination of C and Gave; and interestingly, a certain compaction for the above effect took place at a relatively high shear, possibly attributed to increasingly pronounced occurrence of floc breakage and irreversibility of this behavior. To produce fractal flocs with favorable morphological characteristics, the impeller should be placed at an appropriate distance from the reactor bottom within the flocculating system, under whether aggregation-dominated or breakage-dominated circumstances, for weakening the role of reactor bottom and water surface on floc growth behaviors during flocculation. This research would be beneficial for thoroughly understanding floc formation mechanisms and optimally designing impeller-based flocculating reactors.

A highly efficient conditioning process to improve sludge dewaterability by combining calcium hypochlorite oxidation, ferric coagulant re-flocculation, and walnut shell skeleton construction

High levels of extracellular polymeric substances (EPS) and bound water in sludge negatively impact sludge dewaterability. This study applied a novel sludge conditioning process involving calcium hypochlorite (Ca(ClO)2) oxidation, ferric coagulant re-flocculation, and walnut shell (WS) skeleton construction to remove EPS and bound water and improve sludge dewaterability. The study also described the underlying mechanisms for this activity, by investigating the changes in EPS distribution, morphological structure, flocs morphology, rheological behavior, and bound water. Using single factor experiments, the optimal dosages of the composite conditioner included 10 mg/g dry solid (DS) of Ca(ClO)2, 60 mg/g DS of ferric chloride (FeCl3) or 100 mg/g DS of polymeric ferric sulfate (PFS), and 600 mg/g DS of WS. Using a novel pressure filtration system, the moisture content of the dewatered sludge cake conditioned with Ca(ClO)2/ferric coagulant/WS was reduced to below 50 wt%. The study described a three-step mechanism for the composite conditioning of sludge. First, protein-like substances and polysaccharide-like materials in the EPS and bound water were degraded by Ca(ClO)2 oxidation. Second, the porous structure and compact flocs were re-flocculated using high charge neutralization and the bridging ability of ferric coagulant. The flowability increased and the viscosity decreased compared with raw sludge. Third, a rigid networked structure was formed by adding the WS skeleton. The combined Ca(ClO)2/ferric coagulant/WS treatment had a significant synergistic effect supporting dewatering. The filter liquor of the combined treatment has a lower impact on the environment. The combined treatment is an appropriate was to treat sludge prior to landfilling and incineration. Furthermore, the economic analysis showed that using the Ca(ClO)2/FeCl3/WS treatment had economic advantages over other treatments.

Overcoming floc formation limitations in high-rate activated sludge systems

High-rate activated sludge (HRAS) is an essential cornerstone of the pursuit towards energy positive sewage treatment through maximizing capture of organics. The capture efficiency heavily relies on the degree of solid separation achieved in the clarifiers. Limitations in the floc formation process commonly emerge in HRAS systems, with detrimental consequences for the capture of organics. This study pinpointed and overcame floc formation limitations present in full-scale HRAS reactors. Orthokinetic flocculation tests were performed with varying shear, sludge concentration, and coagulant or flocculant addition. These were analyzed with traditional and novel settling parameters and extracellular polymeric substances (EPS) measurements. HRAS was limited by insufficient collision efficiency and occurred because the solids retention time (SRT) was short and colloid loading was high. The limitation was predominantly caused by impaired flocculation rather than coagulation. In addition, the collision efficiency limitation was driven by EPS composition (low protein over polysaccharide ratio) instead of total EPS amount. Collision efficiency limitation was successfully overcome by bio-augmenting sludge from a biological nutrient removal reactor operating at long SRT which did not show any floc formation limitations. However, this action brought up a floc strength limitation. The latter was not correlated with EPS composition, but rather EPS amount and hindered settling parameters, which determined floc morphology. With this, an analysis toolkit was proposed that will enable design engineers and operators to tackle activated solid separation challenges found in HRAS systems and maximize the recovery potential of the process.

Garden cress mucilage as a potential emerging biopolymer for improving turbidity removal in water treatment

Abstract Agricultural anthropogenic processes have resulted in high turbidity to nearby river water. This study aims to study the possibility and mechanism of biopolymer extracted from garden cress (Lepidium Sativum sp.) seed as natural coagulant aid in a point source agriculture wastewater discharge. Various physico-chemical characterisation studies were conducted i.e. functional group, zeta potential and surface floc morphology. FTIR spectra results indicated the biopolymer was assigned to band peaks at for hydroxyl, carboxyl groups. Whilst, zeta potential was around −16 mV, describing its anionic nature. The morphologies study depicted that the addition of biopolymer produced a more compact and larger structure of the settled sludge. Influence of pH, dosage of Fe3+ and biopolymer were studied in synthetic kaolin and agricultural wastewater using factorial design. pH, dosage of Fe3+ and biopolymer significantly affect the turbidity removal in coagulation process with p-value

Determining the effects of polyaluminum chloride alkalinities and dosage treatments on various microalgal growth phases for the treatment of microalgae-laden water

Harmful algal blooms have become critical threats to human health as they have occurred with increasing frequency and intensity in various water bodies. In the People’s Republic of China, thousands of people are exposed to water bodies heavily contaminated with microalga Microcystis aeruginosa and thus at grave risk of microcystin poisoning. This study investigated the characteristics of extracellular organic matters (EOMs), floc morphology, and microcystin in each microalgal growth phase for the treatment of microalgae-laden water. The characterization was performed under different alkalinities and dosage treatments of polyaluminum chloride (PAC). Results suggested fulvic-like and humic-like acids, CC, and unsaturated aldehyde ketones were present in the supernatant liquor and dissolved EOM (dEOM) solution under logarithmic and stationary phase treatments for EOM. However, the same components along with aromatic protein and amidogen were detected in the supernatant liquor and dEOM solution under the decline phase treatments. The EOM of the supernatant liquor and dEOM solution nearly resembled willmigerl, which was different from bound extracellular organic matter (bEOM) in the three growth phases. Nonetheless, the highest particle size and most compact and roughest flocs were observed in the stationary phase. Meanwhile, no significant difference (P > 0.05) was observed among the microcystin concentrations of microalgal cells before and after coagulation, although the concentrations increased after the coagulating treatment. Therefore, coagulation pH of 2.0 and 50 mg L−1 dose of PAC was a good practical application to treat microalgae laden water at the stationary growth phase.