Polyelectrolyte Flocculation Research Articles

Ultra-High-Molecular-Weight, Narrow-Polydispersity Polyacrylamides Synthesized Using Photoiniferter Polymerization to Generate High-Performance Flocculants.

Ultra-high-molecular-weight, water-soluble polyelectrolytes are commonly employed as flocculants for solid-liquid separation via colloidal destabilization, enabling the rapid and efficient removal of particulate matter from wastewater streams. A drive toward more sustainable and less polluting industrial practices, coupled with the desire to reduce freshwater usage and improve closed-loop systems, demands the development of flocculants with ever-higher dewatering dose performance. Herein, the use of trithiocarbonate-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization under either blue LED (λmax = 470 nm) or UV (λmax = 365 nm) irradiation, known as photoiniferter polymerization, was successfully utilized to generate ultra-high-molecular-weight (Mn > 1,000,000 g mol-1) polyelectrolyte copolymer flocculants with narrow molecular weight distributions (Mw/Mn < 1.2). Cationic and anionic polyelectrolyte flocculants were synthesized containing various monomer compositions of acrylamide (AM), dimethylacrylamide (DMA), 3-(acryloyloxyethyll)trimethylammonium chloride (DMAEAq), 3-(acrylamidopropyl)trimethylammonium chloride (APTAC), sodium acrylate (NaAA), and sodium 2-(acrylamido)-2-methylpropylsulfonate (NaATBS) with high monomer conversion using simple experimental apparatus. The narrow molecular weight distribution cationic polyelectrolytes showed improved flocculation efficiency in the clarification of kaolin suspensions of up to 50% in comparison to a broad polydispersity (Mw/Mn > 5.0) commercial benchmark with an equivalent number average molecular weight. The improved performance of the narrow-polydispersity copolymers is attributed to the reduction in the content of the lower-molecular-weight polymer chains, which impart lower flocculation performance.

Shear Enhanced Flotation Separation Technology in Winery Wastewater Treatment

The process of wine making is well known to produce large amounts of wastewater with highly variable characteristics. The disposal of untreated winery wastewater is strictly prohibited since it adversely affects the recipient environment. Due to the variability in characteristics of winery wastewater, developing a treatment system which can handle high organic and inorganic loads, especially during the vintage season, is a complex challenge. This study investigated the theory, methodology and implementation of a wastewater treatment technology called shear enhanced flotation separation (SEFS) as a potential primary treatment stage towards the treatment of winery wastewater. Winery effluent was subjected to a coagulation process in a high shear environment, with and without the introduction of air, followed by flocculation. Upon successful optimization of operating parameters, a polymeric-based coagulant AB121 and polyelectrolyte flocculant AB796 yielded the highest reduction in turbidity (95%) with typical values of 630 NTU for the raw wastewater and 25 NTU for the SEFS-treated effluent. A substantial reduction in total suspended solids (97%) was achieved with average raw winery wastewater values of 2275 mg/L compared to the 50 mg/L obtained for the SEFS-treated effluent. Furthermore, a notable reduction (54%) in COD (from 11,250 mg/L to 5220 mg/L) using SEFS technology was achieved.

Evaluación de polisacáridos en floculación mediada por complejo polielectrolítico

Water is an increasingly valuable resource because its availability, primarily it is limited to precipitation and water storage; for that reason, increasing population density and climate change can interfere with water accessibility. Urban and industrial activities can produce wastewater and pollute waterbodies that could represent a significant water source; however, it needs to be treated prior to its use. Flocculation is an important pollutants removal method to reduce a variety of organic and inorganic molecules from wastewater, using the flocculant’s intrinsic charges to stabilize/precipitate them, by different methods, one of them being via polyelectrolyte complex. Flocculant versatility depends on its capacity to remove pollutants and there are commercial flocculants with remarkable efficiencies. However, their toxicity can limit their use in waterbodies or for former human use. Research shows that polysaccharides are great option as flocculants because of their easily charged conformation and high molecular weight to neutralize pollutants and precipitate flocs, they are biocompatible, biodegradable, and easy to modify to modulate the flocculant interaction due to the functional group’s high density. This review explores the latest research on polysaccharide polyelectrolyte flocculation and derivatives and their pollutant removal capacity, the polysaccharides evaluated were the most commonly researched such as chitosan, cellulose, chitin, alginate, gums, dextran, among others. Recent research tendencies on these polysaccharides flocculation capacity, showed promising results (up to 99% removal efficiencies) with a wide variety of contaminants, making them excellent candidates for their application in green flocculation.

Fabrication of salt-tolerant chitosan-based polyelectrolyte flocculant through enhancing H-bond hydration effect for treating and recycling of highly saline dyeing wastewater

The textile industry is required to execute water conservation and contamination management techniques owing to increasingly serious water scarcity and pollution. Herein, a novel salt-tolerant chitosan-based flocculant (CT-CTA-BGE3) with high charge density was synthesized through chitosan (CT) etherification with 2,3-epoxypropyl trimethylammonium chloride (CTA) and butyl glycidyl ether (BGE). The H-bond hydration effect between BGE segments and water molecules weakens the salt-induced polyelectrolyte effect, allowing CT-CTA-BGE3 to chains keep an extended conformation in high-salty aqueous solution and thus endowing excellent salt-tolerant properties. Meanwhile, the incorporation of CTA segments offers a high positive charge on the flocculant surface. Thus, the beneficial effect of satisfying color removal was obtained by CT-CTA-BGE3 in a highly saline system because it would render the more exposed active sites with strong positive charges along stretched polymer chains. The outstanding flocculability of CT-CTA-BGE3 (3054 mg/g) for the reactive brilliant red 2 (a widely commercial grade dye) could be obtained within 5 min (pH = 6). As expected, because the CT-CTA-BGE3 impurities can be reduced in reclaimed water via the pH-mediated hydrophilicity-hydrophobicity switch of polymer, the obtained clarified saline wastewater after flocculation can be recycled in a new dyeing bath without sacrificing fabric quality (ΔE*less than1), and over 88 % of NaCl can be regenerated for each cycle. This work develops an alternative strategy for the fabrication of salt-tolerant flocculants through enhancing H-bond hydration, revealing the promising application prospects in treating and recycling highly saline textile wastewater.

First cadmium coordination compound as an efficient flocculant for Congo red

• New Cd(II) coordination compound of 2-phenylimidazo[4,5- f ][1,10]phenanthroline was synthesized via hydrolysis of acetonitrile to acetate. • This compound proves to be the first coordination compound for rapid, specific and complete flocculation of Congo red. • The flocculation mechanism is rationally proposed based on various methods. A cadmium coordination compound, [Cd(pip) 2 (OAc) 2 ]·H 2 O (pip is 2-phenylimidazo[4,5- f ][1,10]phenanthroline), has been successfully synthesized hydrothermally through an in situ hydrolysis of acetonitrile to acetate, and structurally characterized. This compound was found to be able to flocculate Congo red (CR) rapidly and almost quantitatively at pH 7 with low dosage, representing the first coordination compound of such capability. Based on various criteria including infrared spectra, thin layer chromatography and zeta potential analysis, the flocculation mechanism has been proposed to involve displacement of acetate in the complex by CR anion and successive hydrogen bonding and bridging effect, different from the mechanism for traditional polyelectrolyte flocculants.

Separation of Halloysite Nano Tubes (HNTs) by Homogenization of Quartz Contaminated Kaolins

Natural halloysite kaolin contains a lot of impurities such as quartz phases and varies in morphology and size during their formation in the earth. So to utilize as a new type of natural nano material, removing quartz impurities from kaolin clays without scathe the tube morphologies are necessary. So to remove quartz impurities from kaolin by forming a well deflocculated aqueous slip without fracturing the morphology of tubes, the slip of homogenized halloysite clay was recovered by adding polyvalent metallic cations and anionic polyelectrolyte flocculants simultaneously to selectively flocculate the mixture of quartz and halloysite, whereby the halloysite particles form floes and the tubular halloysite remains in suspensions. Then, the uniform size and tubular shape of halloysite was obtained which could be suitably used as a container or a carrier to encapsulate nanomaterials.

Detoxification of dilute ammonia pretreated energy cane bagasse enzymatic hydrolysate by soluble polyelectrolyte flocculants

This study investigated the detoxification of dilute ammonia pretreated energy cane bagasse enzymatic hydrolysate using polyelectrolyte flocculants. Non-sugar compounds such as formic acid, acetic acid, levulinic acid, furfural, 5-hydroxymethylfurfural (HMF), and phenolic compounds can be generated during pretreatment, which have negative effects on downstream processes. Flocculation was carried out to remove these non-sugar compounds while retaining the fermentable sugars. The flocculants polyethylenimine (PEI) and poly-diallyldimethylammonium chloride (pDADMAC) were used and parameters including flocculant dose and hydrolysate pH were evaluated. The recyclability of PEI and recovery of non-sugar compounds were also assessed. Optimum conditions for both PEI and pDADMAC were 15 g/L dose at unadjusted pH 4.5. At these conditions, PEI outperformed pDADMAC by having greater adsorption efficiencies towards non-sugar compounds with minimal sugar losses. PEI removed 43% organic acids, 73% total phenolic compounds and 100% furans with less than 10% total fermentable sugar losses. However, after two cycles, only 20% of the adsorbed organic acids and total phenolic compounds, and 80% of the furans were recovered. Sugar losses of less than 10% were observed throughout the recycling process. PEI can significantly remove the non-sugar compounds from dilute ammonia pretreated energy cane bagasse enzymatic hydrolysate with minimum sugar losses. However, recycling of PEI and recovery of adsorbed non-sugar compounds are not recommended for more than two cycles.

In situ polymer flocculation and growth in Taylor-Couette flows.

Flocculation of small particulates suspended in solution is a key process in many industries, including drinking water treatment. The particles are aggregated during mixing to form larger aggregates, known as flocs, through use of a polyelectrolyte flocculant. The flocculation of these particulates in water treatment, however, are subject to a wide spatial variation of hydrodynamic flow states, which has consequences for floc size, growth rate, and microstructure. Floc assembly dynamics are explored here using a commercially available cationic polyacrylamide, commonly used in water treatment, and anisotropic Na-bentonite clay particles under a variety of hydrodynamic mixing conditions. A Taylor-Couette cell with the unique ability to radially inject fluid into the rotating annulus was used to study how specific hydrodynamic flow fields affect assembly and structure of these materials during the flocculation process. Faster floc growth rates and decreased floc fractal dimensions were observed for higher order flow states, indicating improved mass transfer of the polymer flocculant and breakage at the edges of the flocs (shear rounding), respectively. This work sheds more light on the complexities of polymer-induced flocculation, towards improving dosing and efficiency of large-scale operations.

Separation of saccharides from prehydrolysis liquor of lignocellulose to upgrade dissolving pulp mill into biorefinery platform

In this work, a competitive process consisting of polyelectrolyte flocculation, active carbon absorption, and ion exchange was developed for hemicelluloses-derived saccharides (HDSs) purification from prehydrolysis liquor (PHL) of lignocellulose. Results showed that colloidal lignin counted for 20% of non-saccharide compounds (NSCs) and could be eliminated by flocculation at 500mg/L polyaluminium chloride and 50mg/L anionic polyacrylamide. Active carbon was very effective for decoloration of flocculation-treated PHL, but showed limited absorption selectivity toward NSCs. Lignin, the dominant component of NSCs, is characterized with phenolic hydrogen groups. Phenolic lignin could be easily captured by anion exchange resin with 80% removal. The proposed process showed great industrial potential because of the high value saccharides, but also low molecular phenolic lignin.

Polyamphoteric flocculants for the enhanced separation of cellular suspensions

The efficient concentration and separation of microorganisms from dilute culture suspensions is crucial to the success and productivity of many biotechnological processes. This article presents the design and characterization of polyamphoteric flocculants with a tunable, zwitterionic character for the enhanced separation of biocolloidal suspensions of yeast, wastewater, microalgae, and potentially other cellular systems. The polyamphoteric flocculants have overall molecular charges dependent upon the system pH, thereby providing a strong electrostatic attraction to the diverse but predominantly negatively-charged cellular surfaces of the biological suspensions. The polyamphoteric flocculants with tailored charge character are shown to have higher flocculation efficiencies than comparable cationic polyelectrolytes, and have an enhanced ability to 1) adsorb to the diverse range of charge character in cellular suspensions, 2) operate over an extended range of suspension pHs, and 3) operate at lower flocculant concentrations. These enhanced flocculation properties are shown to arise, perhaps counterintuitively, due to interactions between the negatively-charged functionality on the flocculant and the predominantly negatively-charged biocolloids. Statement of SignificanceThis article presents the design and characterization of polyamphoteric flocculants for the separations of biocolloidal suspensions of importance in the production of biopharmaceuticals, microalgal cultures for nutraceuticals and biofuels, and wastewater treatment. The polyamphoteric flocculants consist of tunable, mixed charges dependent upon system pH, thereby providing strong electrostatic attraction to the diversely-charged surfaces of cellular suspensions. Enhanced flocculation efficiencies are achieved, as compared to cationic polyelectrolyte flocculants, and result from the ability of polyampholytes to adsorb to a diverse range of charge character and operate over an extended range of pH conditions.

The combination of KMnO4 oxidation and polymeric flocculation for the mitigation of membrane fouling in a membrane bioreactor

KMnO4 oxidation combined with polyelectrolyte (K530CF) flocculation was investigated to mitigate membrane fouling in a membrane bioreactor. The optimum dosages of chemical additives in order to enhance the removal of soluble microbial products (SMPs) were determined. This method was able to reduce the concentration of COD in the effluent to 57.1% and 51.1% lower than those in the experiments in the absence of chemical flocculants and in the presence of polyelectrolyte, respectively. NH3-N removal was improved by combining KMnO4 and K530CF. When KMnO4 was used along with polyelectrolyte, the zeta potential was neutralized to a greater extent which resulted in an improvement in the flocculation process which subsequently increased the size of the flocs. It was also observed that the SMP of the mixed liquor decreased through entrapment into formed flocs and adsorption by manganese dioxide particles. Increase of the particle size and reduction of the SMP compounds together lead to the reduction of the cake layer resistance. When compared to the experiments in the absence of chemical additives and with polyelectrolyte, KMnO4 in conjunction with polyelectrolyte increased the membrane operating time by about 4 and 2.7 times, respectively. These findings confirmed that KMnO4 along with polyelectrolyte significantly reduced membrane fouling.

A low-cost solid–liquid separation process for enzymatically hydrolyzed corn stover slurries

Solid–liquid separation of intermediate process slurries is required in some process configurations for the conversion of lignocellulosic biomass to transportation fuels. Thermochemically pretreated and enzymatically hydrolyzed corn stover slurries have proven difficult to filter due to formation of very low permeability cakes that are rich in lignin. Treatment of two different slurries with polyelectrolyte flocculant was demonstrated to increase mean particle size and filterability. Filtration flux was greatly improved, and thus scaled filter unit capacity was increased approximately 40-fold compared with unflocculated slurry. Although additional costs were accrued using polyelectrolyte, techno-economic analysis revealed that the increase in filter capacity significantly reduced overall production costs. Fuel production cost at 95% sugar recovery was reduced by $1.35 US per gallon gasoline equivalent for dilute-acid pretreated and enzymatically hydrolyzed slurries and $3.40 for slurries produced using an additional alkaline de-acetylation preprocessing step that is even more difficult to natively filter.

Flocculation of natural turbid water by amide-, carboxyl-or amine-containing polyelectrolytes

The flocculation of natural turbid water with various concentrations of suspended solids in the presence of high-molecular polyelectrolyte flocculants different in location, density, quantity and charge of functional group in the macromolecule chain as well as in the presence of aluminum sulfate coagulant was studied. The interaction processes between flocculants and suspended solids in natural turbid water were shown to be identical but different from its interaction with low-molecular aluminum sulfate coagulant.

Evaluation of Natural Flocculants for Conventional Water Treatment

Drinking water is contaminated from the chemicals and biological impurities around the world mostly in rural area. These contaminations may come from natural sources and leaching of waste deposits which cause a major human health hazard in many parts of the world. There has been very little scientific research work into the use of natural flocculants to purify raw water. Most of the research studies that have been done on conventional water purification in developing countries have focussed on conventional water purification systems using inorganic and poly-electrolyte flocculants. Such systems are very expensive for rural communities in these developing countries as our objective is to provide water that is safe for human consumption by using facilities which can be constructed and operated at a reasonable cost. There is a need to evaluate natural flocculants for conventional water treatment in order to develop inexpensive ways for developing countries to purify their water. In this study, the natural flocculants such as Moringa seeds powder, Guar Gum seeds powder, aluminium sulphate and polyelectrolyte were tested in a jar test apparatus to determine the optimum operating conditions for water or wastewater treatment plants. The results showed that the addition of Moringa Oleifera seeds powder, Guar Gum seeds powder, aluminium sulphate and polyelectrolyte flocculants improved the quality of raw water. The raw water samples from all treatment plants showed a reduction in turbidity that was more than 70% when all the four flocculants applied synergistically.

Adição de polieletrólito ao processo de floculação no pós-tratamento de lixiviado por coagulação-floculação-sedimentação

A adição de polieletrólito ao processo de floculação no tratamento físico-químico por coagulação-floculação-sedimentação de efluentes tem sido uma alternativa para a obtenção de clarificados de boa qualidade em menor tempo devido ao aumento da velocidade de sedimentação. Deste modo, este artigo, objetivou determinar as inter-relações entre as variáveis pH, gradiente de floculação, dosagem de ferro e tipo de polieletrólito e avaliar o efeito desta adição na remoção de cor, DQO e turbidez no pós-tratamento do lixiviado submetido a tratamento biolõgico. Através do uso da técnica de planejamento e analisando-se os resultados obtidos, pôde-se verificar que o polímero de carga catiônica apresentou-se como o mais eficiente, obtendo remoções de até 97,70% para cor verdadeira, 81,52% para DQO e 92,18% para turbidez.

Pigment removal in anaerobically digested effluent through polyelectrolyte flocculation and liquid-liquid extraction

BACKGROUND: Use of flocculation in wastewater treatment involves interactions of polymer with suspended solids and some dissolved organic compounds that can have a significant impact on aggregation process. RESULTS: It was found that a strong interaction between cationic compounds and dissolved pigments in anaerobically digested (AD) wastewater occurred. The interactions were investigated by light adsorption of the pigments using a commercial flocculant added in the solutions and through a liquid–liquid extraction method using a model cationic surfactant (CTAB) dissolved in organic solvents. The absorbance of pigments decreased significantly with added cationic flocculant as the pigments and flocculants formed insoluble complexes that were removed by centrifugation. CONCLUSION: The absorbance results indicate that the pigments can form complexes even at high concentrations (e.g. 2000 mg L−1) of the flocculants. In addition, the extraction results demonstrated that pigments in the aqueous phase were transferred into the CTAB organic phase due to a strong interaction between the pigments and CTAB. These results suggest that the pigments present in AD effluent could be a negative factor for the flocculation process, probably resulting in the need for a high dosage of flocculants. Copyright © 2012 Society of Chemical Industry

Polyelectrolyte Flocculation of Waste Activated Sludge in Decanter Centrifuge Applications: Lab Evaluation by a Centrifugal Compaction Test

This article introduces a centrifugal compaction (spin tube) test to thoroughly evaluate polyelectrolyte conditioning on lab scale. In contrast to the well-known and widely applied existing tests (e.g., the beaker, the Jar settling, the free drainage, and the [sheared] capillary suction time test), the proposed spin tube test has a clear relation with the dewatering process taking place in a decanter centrifuge. First, based on the theory of centrifugal compaction, the solids stress of separate layers of sludge cake (obtained after spinning sludge in a lab centrifuge) is calculated. Next, the test was applied to assess in the lab the performance of three different polymers by evaluating the obtained sludge dryness. To verify and/or compare the results obtained with the spin tube tests, sheared capillary suction time tests were conducted and floc size distributions were analyzed. Finally, two of the three polymers evaluated in the lab were applied in the industrial sludge dewatering and drying system used at the wastewater treatment plant of Monsanto Antwerp in Belgium. Observed field performance was in perfect accordance with the spin tube tests.

Ecotoxicological assessment of a polyelectrolyte flocculant

Flocculant blocks are commonly used as a component of (passive) water treatment systems to reduce suspended sediment loads in the water column. This study investigated the potential for aquatic biological impacts of a flocculant block formulation that contained an anionic polyacrylamide (PAM) active ingredient and a polyethylene glycol (PEG) based carrier. The toxicity of the whole flocculant block was assessed and the individual components of the block were also tested separately. Five Northern Australian tropical freshwater species (i.e. Chlorella sp. Lemna aequinoctialis, Hydra viridissima, Moinodaphnia macleayi and Mogurnda mogurnda) were exposed to a range of concentrations of the whole flocculant block, and of the individual PAM and PEG components. The concentration of Total Organic Carbon (TOC) in solution was used to provide a measure of the total amount of PAM and PEG present. An extremely wide range of toxic responses were found, with the flocculant blocks being essentially non-toxic to the duckweed, fish and algae (IC 50 > 1880 mg l −1 C TOC, IC 10 > 460 mg l −1 C TOC), slightly toxic to the hydra (IC 50 = 610–2180 mg l −1 C TOC, IC 10 = 80–60 mg l −1 C TOC) and significantly more toxic to the cladoceran (IC 50 = 10 mg l −1 C TOC, IC 10 = 4 mg l −1 C TOC). More detailed investigation of the two components indicated that the PAM was the primary “toxicant” in the flocculant blocks. Derived Protective Concentrations (PCs) for the flocculant blocks, expressed as equivalent TOC concentrations, were found to be lower than typically measured natural environmental concentrations of TOC. It will thus be possible to use TOC as measure of the concentration of PAM only in those situations where lower levels of ecosystem protection (i.e. higher PCs) are applicable.

Temperature responsive flocculation and solid–liquid separations with charged random copolymers of poly(N-isopropyl acrylamide)

Temperature-responsive random copolymers based on poly(N-isopropyl acrylamide) (PNIPAM) with 15mol% of either acrylic acid or dimethylaminoethyl acrylate quaternary chloride were prepared. The effect of the charge and its sign were investigated in the solid–liquid separation of silica and alumina mineral suspensions. The results were compared to PNIPAM homopolymer of similar molecular weight. PNIPAM copolymers of the same charge as the particles (co-ionic PNIPAM) act as dispersants at both 25°C and 50°C. Flocculation occurs when counter-ionic PNIPAM facilitates selective aggregation and rapid sedimentation of minerals at both 25°C and 50°C. Adsorption and desorption studies showed that, unlike non-ionic PNIPAM, little desorption of the counter-ionic copolymers from the oxides occurred after cooling a suspension from 50°C to below the lower critical solution temperature. Thus, incorporation of counter-ionic charge into the temperature sensitive polymer PNIPAM was found to reduce the sediment bed consolidation upon cooling when compared to PNIPAM homopolymers. The lack of secondary consolidation upon cooling is attributed to attractive inter-particle forces, such as conventional polyelectrolyte flocculation mechanisms (bridging, charge neutralization or charge patch) which persist at both 25°C and 50°C when counter-ionic PNIPAM is used. On the other hand, it was possible to obtain rapid sedimentation with the counter-ionic PNIAPMs even when they were added to the suspension already at 50°C, a process which has not been possible with neutral PNIPAM homopolymers.

Marine microalgae flocculation and focused beam reflectance measurement

The production of biodiesel from fast growing and lipid containing marine microalgal species is sustainably and economically more promising than fresh water microalgae. However, like fresh water microalgae, the process is limited by numerous factors such as the generally dilute nature of microalgal cultures, and the small size of microalgae cells, except for multi-cellular species such as Spirulina. Current dewatering technologies are sufficiently able to separate microalgae from the culture media; however the economics of the process makes these technologies ineffective as they are all too expensive when compared with the low cost of biodiesel from other sources. Centrifugation, which is one of the current technologies, is highly energy intensive especially in a large-scale setting. Filtration techniques such as tangential flow filtration has the potential to be a low cost dewatering technique, however there is a cost issue associated with the replacement of clogged membranes. Flocculation is another commonly used dewatering technique that has the advantage of using less energy under optimum conditions. Thus process development for marine microalgae flocculation could be an essential step to revolutionize biodiesel production from microalgae. In this work, mixed cultures of marine microalgal species were obtained from semi-continuous laboratory reactors and flocculation was investigated using polyelectrolyte (polymer) flocculants. Cationic, anionic and non-ionic polyelectrolyte flocculants were tested using the standard jar stirrer test at varying pH and temperature. All three flocculant types displayed suitability for microalgae flocculation with the cationic polymer obtaining the highest flocculation efficiency of 89.9% at an optimum concentration of 4 mg/L. Focused beam reflectance measurements (FBRM) showed real time changes in microalgal flocs size during the flocculation process. This data is essential to understand the kinetics of microalgal flocs formation, to ensure the stability of the floc formation process, and to monitor and evaluate the performance of the flocculation process.