Coagulation-flocculation Mechanism Research Articles

Avocado seed as a natural coagulant for removing dyes and turbidity from wastewater: Behnken Box design, sustainable reuse, and economic evaluation

In wastewater treatment, conventional coagulants are becoming very complex with environmental concerns. For this purpose, using an alternative natural coagulant such as fruit waste becomes essential. This study explores the potential of avocado seed powder as a novel biocoagulant for treating wastewater contaminated with dyes and turbidity. It was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, Scanning Electron Microscopy coupling with Energy-dispersive X-ray spectroscopy, and X-ray fluorescence. The coagulation-flocculation process was optimized using a Box-Behnken design, evaluating the effects of coagulant dose (300–1000 mg. L−1), initial solution pH (3–9), and granulation (63–112 μm), on the removal of methylene blue, crystal violet, and turbidity. The response surface methodology revealed statistically significant quadratic models (R2 > 0.94) for maximizing pollutant removal. Under optimal conditions (1000 mg. L−1 dose, pH 9, 63 μm granulation for methylene blue; 950 mg. L−1, pH 7, 108 μm for crystal violet; 300 mg. L−1, pH 8, 63 μm for turbidity), avocado seed powder achieved maximum removal efficiencies of 94.34 % for methylene blue, 95.28 % for crystal violet, and 99.64 % for turbidity. Characterization techniques confirmed the involvement of avocado seed powder in the coagulation-flocculation mechanism. The biocoagulant has demonstrated significant reuse potential over five cycles. It also has a low estimated cost, of the order of 0.008–0.025 USD. m−3 as agricultural waste, compared with 1.5 USD. m−3 for aluminum sulfate. Overall, avocado seed is a sustainable and promising natural coagulant for wastewater treatment.

Ultra-high flux catalytic membrane reactors based on coagulation-flocculation mechanism for selective catalytic

Catalytic membrane reactors (CMRs), combination of catalytic industry and membrane technology, facilitates manufacture efficiency in massive practical and industrial applications. However, the balance of membrane flux and catalytic performance represents enormous challenges. Herin, we propose the coagulation-flocculation strategy for piloting the Zeta potential on CMR with the flow-reaction channel by modulating the filler within the mixed matrix membrane. Comprehensive characterizations demonstrate that the modulation of zeta potential in the CMR triggers the regulation of channel environment (interconnected macro-pore network structure) with the formation of more catalytic sites. Both the experimental outcomes and reaction mechanism explicitly validate the facilitating role of channel environment in boosting the enrichment of reactants and selectivity for reactants, thereby substantially stimulating the reactants activation for the subsequent catalytic procedure more feasibly. The CMR presents superior performance in the catalytic discoloration of contaminations (the flux record-value of 8664 L m−2 h−1, catalytic efficiency: 98.5 %, and robust stability: 15 cycles in Methylene Blue (MB) tests, and brilliant selectivity for various reactants with charge selectivity and size selectivity). This controllable adjustment of the membrane structure based on the coagulation-flocculation mechanism shines tactic for design high-flux, high-efficiency CMR for industrial preparation.

Coagulation–flocculation mechanism and characterisation of Hylocereus undatus foliage as a natural coagulant in industrial wastewater treatment

Coagulation–flocculation mechanism and characterisation of Hylocereus undatus foliage as a natural coagulant in industrial wastewater treatment

Aleppo pine seeds (Pinus halepensis Mill.) as a promising novel green coagulant for the removal of Congo red dye: Optimization via machine learning algorithm

Consideration is now being given to the use of metal coagulants to remove turbidity from drinking water and wastewater. Concerns about the long-term impact of non-biodegradable sludge on human health and the potential contamination of aquatic systems are gaining popularity. Recently, alternative biocoagulants have been suggested to address these concerns. In this study, using a 1 M sodium chloride (NaCl) solution, the active coagulating agent was extracted from Pinus halepensis Mill. Seed, and used for the first time to remove Congo red dye, the influence of numerous factors on dye removal was evaluated in order to make comparisons with conventional coagulants. The application of biocoagulant was shown to be very successful, with coagulant dosages ranging from 3 to 12 mL L−1 achieving up to 80% dye removal and yielding 28 mL L−1 of sludge. It was also found that biocoagulant is extremely pH sensitive with an optimum operating pH of 3. Ferric chloride, on the other hand, achieved similar removal rate with higher sludge production (46 mL L−1) under the same conditions. A Fourier Transform Infrared Spectroscopy and proximate composition analysis were undertaken to determine qualitatively the potential active coagulant ingredient in the seeds and suggested the involvement of proteins in the coagulation-flocculation mechanism. The evaluation criteria of the Support vector machine_Gray wolf optimizer model in terms of statistical coefficients and errors reveals quite interesting results and demonstrates the performance of the model, with statistical coefficients close to 1 (R = 0.9998, R2 = 0.9995 and R2 adj = 0.9995) and minimal statistical errors (RMSE = 0.5813, MSE = 0.3379, EPM = 0 0.9808, ESP = 0.9677 and MAE = 0.2382).The study findings demonstrate that Pinus halepensis Mill. Seed extract might be a novel, environmentally friendly, and easily available coagulant for water and wastewater treatment.

Parametrical Study for the Effective Removal of Mordant Black 11 from Synthetic Solutions: Moringa oleifera Seeds’ Extracts Versus Alum

Prior studies have examined the ability of Moringa oleifera (MO) seed extract, among other natural coagulants, to remove several types of dyes. MO has been proven to have a high capacity to remove some anionic dyes. The aim of the present study is to explore the possible use of aqueous and saline extracts of MO as biocoagulants for the removal of Mordant Black (MB11) from aqueous solution. Their performances were compared to that of aluminum sulfate (alum). To do so, various operating parameters were investigated such as coagulant dose (100–600 mg/L), pH (3–11), initial dye concentration (100–350 mg/L), sodium chloride concentration (0.2–2 M), and sedimentation time (15–90 min). The maximum percentages of MB11 removal were found to be 98.65%, 80.12%, and 95.02% for alum, aqueous extract of MO (MOPW), and saline extract of MO (MOPS), respectively, at around pH 6.5 and for coagulant doses of 400 mg/L (alum) and 500 mg/L (MOPW and MOPS). The coagulation-flocculation mechanism of biocoagulants was hypothesized to be adsorption and charge neutralization. The two biocoagulants (MOPW and MOPS) showed an interesting versatility towards pH counter to alum which was very sensitive to this parameter. pH variations were measured for the three coagulants and proven to be negligible for the biocoagulants. Faster sedimentation time was recorded when MOPW and MOPS were used, suggesting the existence of larger quickly settleable flocs. Considering their high coagulative capacity, rapid and cost-effective preparation, and eco-friendly character, MO extracts can be considered as powerful alternatives to aluminum sulfate in the remediation of MB11 from wastewaters.

Elucidation the influence of design variables on coagulation–flocculation mechanisms in the lab-scale bio-coagulation on toxic industrial effluent treatment

Bio-coagulants are environmentally friendly substances that have shown potential in removing organic and inorganic contaminants from wastewater from the Imitation Paint Industry. Under the optimized conditions, the use of the three bio-coagulants (of plant origin), Strychnos potatorum, Cactus opuntia and Portunus sanguinolentus (crab) shell (of animal origin) were evaluated, and their removal mechanism was based on kinetic models and adsorption isotherms. The error analysis method was used to find the best isotherm fit. In addition, the kinetic model parameters showed the absence of chemisorption and confirmed the existence of pore diffusion. The interaction between coagulant and pollutant, the type, homogeneity and intensity of the coagulation process, the pollutant absorption capacity of the coagulant were evaluated with the aid of the adsorption isotherm models. From the Pseudo first-order kinetic model an equilibrium pollutant uptake (mg/g) was marked as 598, 554 and 597 for Strychnos potatorum, Cactus opuntia and Portunus sanguinolentus respectively. The better affinity between the pollutants and the bio coagulants were observed through the lower values of Langmuir isotherm constant kL. The adsorption intensity from Freundlich model (nF) were ranged between 1 and 10 for all the listed coagulants, which revealed the physisorption behavior and heterogeneous mechanism of removal. With these results, it would be possible to conduct scale-up studies to adopt the process for practical systems.

Chemically enhanced primary treatment of dairy wastewater using chitosan obtained from shrimp wastes: optimization using a Doehlert matrix design

ABSTRACT Dairy operations generate large volumes of polluted wastewater that require treatment prior to discharge. Chemically enhanced primary treatment (CEPT) is a widely utilized wastewater treatment strategy; but it requires the use of non-biodegradable coagulants that can lead to toxic-byproducts. In this study, chitin from shrimp shell waste is extracted and converted into chitosan. Chitosan was demonstrated to be a natural, low-cost alternative coagulant compatible with the CEPT. Following treatment, dissolved air flotation allowed for the removal of turbidity, COD, and UV254 from the synthetic dairy effluent (SDE). Doehlert matrix was used to optimize the chitosan dosage and pH of the CEPT; as well as to model the process. The mechanisms behind the coagulation-flocculation were revealed using zeta potential analysis. FTIR spectroscopy was utilized to confirm the functional groups present on the chitosan. Chitosan with a degree of deacetylation equal to 81% was obtained. A chitosan dose of 73.34 mg/L at pH 5.00 was found to be optimal for the removal of pollutants. Removals of COD, turbidity and UV254 were 77.5%, 97.6%, and 88.8%, respectively. The amount of dry sludge generated to treat 1 m³ of SDE was 0.041 kg. Coagulation-flocculation mechanisms involved in chitosan-mediated treatment of SDE involve the neutralization of electrostatic charges carried on the amine groups present in cationic chitosan at pH 5.00. Doehlert matrix proved to be a useful tool in optimizing parameters throughout the coagulation-flocculation process. Chitosan from shrimp waste is a low-cost, eco-friendly coagulant alternative for the removal pollutants from dairy effluent using the CEPT.

Interaction between ballasting agent and flocs in ballasted flocculation for the removal of suspended solids in water

The interaction between ballasted agent and flocs formed from coagulation/flocculation process is not well understood. This study sought to understand the interaction between ballasted agent and flocs by investigating the impact of ballasted agent on the flocs formation and subsequently the removal of suspended solids in water. Ballasted flocculation was conducted using jar tests where the dosage of flocculant and sand was varied at 1–4 mg/L and 2–8 g/L, respectively. The turbidity removal peaked (90%) at 2 mg/L of flocculant and 1 g/L of sand. It was observed that excessive dosing of sand resulted in the formation of premature flocs that settled quickly before having the chance to remove more suspended solids via sweep coagulation. This revealed that the ballasted agent would affect the coagulation-flocculation process and subsequently the removal of suspended solids. This study indicates that future research on the impact of the ballasted agent on different coagulation-flocculation mechanism should be explored to ensure the suspended solids could be removed with short settling time and without compromising the quality of treated water.

Anionic reverse microemulsion grafting of acrylamide (AM) on HydroxyEthylCellulose (HEC): Synthesis, characterization and application as new ecofriendly low-cost flocculant

New water-soluble cellulosic derivative based on HEC was successfully elaborated (HECc), and used as anionic coagulant-flocculant of colloidal systems Fe(OH)3 and to remove of heavy metal ions (Cu(II)) from aqueous media. HECc was synthesized in unconventional reverse microemulsion process using water as ecofriendly solvent and as hydrogen transfer agent, where cyclohexane was employed as continuous phase to reduce the hydrophobicity of the medium. The amide groups grafted on HEC main chain were saponified to increase the negative charge density, and then the zeta potential value of HECc derivative reached -45 mV. The proposed structure of HECc was confirmed by FTIR, 1H, 13C NMR and deept-135. The XRD technique was used to study the effect of grafting process on the crystalline order. Moreover, the morphological changes and the elementary composition of the surfaces were studied using scanning electron microscope equipped with EDX. The new HECc coagulant-flocculant showed a high coagulation-flocculation capacity toward Fe(OH)3 colloidal system at 35 μL as added volume of 0.5% flocculant solution. Moreover, the pH values showed an important effect (species distribution) on the coagulation-flocculation mechanism and on the flocculating capacity to remove (Cu (II).

Zeta Potential as a Tool to Evaluate the Optimum Performance of a Coagulation-flocculation Process for Wastewater Internal Treatment for Recirculation in the Pulp and Paper Process

The pulp and paper mill process requires large amounts of water. Therefore, the need to reuse water through the application of coagulation-flocculation processes, which is effective in the removal of solids and colloidal particles, has risen. In such processes, zeta potential (ZP) provides important information about the efficiency of the reagents used. The purpose of this study was to develop individual and combined tests of reagents to study turbidity and COD reduction based on ZP in the process of wastewater internal treatment for recirculation in the pulp and paper process. Factorial models were developed to explain the behavior of ZP depending on the different coagulants/flocculants. The statistical analyses showed that ZP had a positive correlation with parameters related to removal (COD and turbidity). It was demonstrated that innovate use of lentil extract (Lens esculenta) applied with aluminum sulfate favored the treatment, consistent with a coagulation-flocculation mechanism. The optimum doses of lentil extract were able to reduce the requirements of aluminum sulfate by almost 29%, providing an alternative strategy for water reuse processes in the pulp and paper industry.

Preparation and reuse of iron and aluminum oxides activated sewage sludge based coagulants for the post-treatment of up-flow anaerobic sludge blanket reactor effluent

Present study proposed the iron and aluminum oxides activation approach to produce the sewage sludge derived coagulants (SSCs) through the pyrolysis of sewage sludge (SS). Characterization techniques including X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and elemental dispersion X-ray spectroscopy (EDX) were used to investigate the structural change in SSCs. As prepared SSCs were used for the comparative treatment study of up-flow anaerobic sludge blanket (UASB) reactor effluent via coagulation/flocculation process. Response surface methodology was used to optimize the responses namely, chemical oxygen demand (COD) and turbidity removal efficiency influenced by the variables including dose of iron oxide activated SSC, aluminum oxide activated SSC, polymeric composite coagulant ferric aluminum silicate sulfate (PFASS) from the range of 100–500 mg/L and the range of initial pH 7.0–11. Preliminary tests analysis, results of modeling and confirmation tests proved that SSCs exhibited the excellent performance for post-treatment of UASB effluent compared to polymeric coagulant PFASS because activation with pyrolysis enhanced the structures features and metal contents of sludge which favored in coagulation, precipitation, and adsorption. Additionally, sludge itself contains a higher amount of Mg, Ca and Si oxides and/or hydroxides which fairly contributes in the removal process compared to freshly prepared PAFSS. Furthermore, zeta potential study also helpful to understand the bridging of adsorption and charge neutralization during coagulation–flocculation mechanisms and played a crucial role in process optimization via decreased the colloids surface charge. The results of the present study illustrate that iron and aluminum oxides activation is an effective approach for reuse the sewage sludge as coagulants and their reuse for post-UASB reactor effluent treatment as an attractive possibility from waste to resource recovery.

Optimization of the coagulation–flocculation process for the removal of natural organic matter fractions present in drinking water sources

We used an experimental design to determine the best coagulation–flocculation mechanism and the optimal operating conditions for the maximum removal of the natural organic matter fractions (hydrophobic acid (HPOA) and hydrophilic neutral (HPIN)), which are the main factors responsible for irreversible membrane fouling and the generation of disinfection by-products (DBPs). Charge neutralization and sweep mechanisms (SM) were studied using the jar test experiment, and synthetic waters prepared with different hydrophobic/hydrophilic (HPO/HPI) weight ratios by adding model compounds to represent the dissolved organic matter (DOM) fractions. Significant influence factors were identified for both coagulation mechanisms. The SM was the best one for DOM removal independent of the HPO/HPI weight ratio. The SM removed HPOA and HPIN fractions with efficiencies of 87.5–90.5% and 73.6–89.8%, respectively. The dissolved organic carbon (DOC) values of all met the recommendation proposed by the United States Environmental Protection Agency (2 mg total organic carbon (TOC)/L or 1.8 mg DOC/L) for DBPs (<100 μg/L). Furthermore, all effluents met the DOC and silt density index recommended values by membrane suppliers (<3 mg DOC/L and <5%/min, respectively) to minimize fouling potential and to extend the membrane life.

Treatment of radioactive waste seawater by coagulation–flocculation method using ferric hydroxide and poly acrylamide

This work studied a coagulation–flocculation system using ferric hydroxide and poly acrylamide flocculant to find the effective condition to remove the radionuclides of Co, Mn, Sb, Ru, and Sr remaining in solution after Cs removal by adsorption for the treatment of radioactive waste seawater generated in a disastrous nuclear power plant accident like Fukushima Daiichi. The coagulation–flocculation mechanism was studied, and the performance characteristics of the coagulation–flocculation system was evaluated in views of decontamination yield of the elements, residual turbidity of treated solution, settling speed of flocs, and generated total floc volume, etc. The total removal yield of target radio nuclides of Co, Mn, Sb, and Ru was more than 99% in seawater at pH 8.

Perspectives on the use of equilibrium isotherm equations to elucidate coagulation–flocculation mechanisms in plant-based coagulants

Viewpoints on the applicability of the equilibrium isotherm equations in coagulation–flocculation (CF) process are presented herein to stem the tide of the misuse. The two widely used equilibrium isotherm equations (Langmuir and Freundlich equilibrium isotherm equations) have been erroneously used to elucidate the CF mechanism, using plant-based coagulants, without a tenable theoretical basis. This erroneous use of equilibrium isotherm equations in CF process was based on the assumption that adsorption process is the rate determining step in the mechanism of CF process, using plant-based coagulants. This is in contrary to the fact that the rate determining step is a kinetic process, which is different from the equilibrium state.

Coagulation–flocculation mechanisms in wastewater treatment plants through zeta potential measurements

Based on the polyelectrolyte-contaminant physical and chemical interactions at the molecular level, this article analyzed and discussed the coagulation–flocculation and chemical precipitation processes in order to improve their efficiency. Bench experiments indicate that water pH, polyelectrolyte (PE) dosing strategy and cationic polyelectrolyte addition are key parameters for the stability of metal–PE complexes. The coagulation–flocculation mechanism is proposed based on zeta potential (ζ) measurement as the criteria to define the electrostatic interaction between pollutants and coagulant–flocculant agents. Polyelectrolyte and wastewater dispersions are exposed to an electrophoretic effect to determine ζ. Finally, zeta potential values are compared at pH 9, suggesting the optimum coagulant dose at 162mg/L polydadmac and 67mg/L of flocculant, since a complete removal of TSS and turbidity is achieved. Based on the concentration of heavy metals (0.931mg/L Sn, 0.7mg/L Fe and 0.63mg/L Pb), treated water met the Mexican maximum permissible limits. In addition, the treated water has 45mg O2/L chemical oxygen demand (COD) and 45mg C/L total organic carbon (TOC). The coagulation–flocculation mechanism is proposed taking into account both: zeta potential (ζ)–pH measurement and chemical affinity, as the criteria to define the electrostatic and chemical interaction between pollutants and polyelectrolytes.

Synthesis and characterization of a dewatering reagent: cationic polyacrylamide (P(AM–DMC–DAC)) for activated sludge dewatering treatment

ABSTRACT P(AM–DMC–DAC), one kind of ternary copolymerized cationic polyacrylamide, was synthesized using acrylamide (AM), methacryloxyethyltrimethyl ammonium chloride (DMC), and acryloxyethyltrimethyl ammonium chloride (DAC) by photopolymerization technique. The copolymer was characterized by means of Fourier transform infrared spectroscopy, thermal gravimetric analysis, and scanning electron microscopy. The optimum synthesis conditions were as follows: mass percentage of photoinitiator being 0.40%, mass percentage of solubilizer being 0.10%, inducing time being 1 h, pH value being 9.0, and mass ratio of AM/DMC/DAC being 4:3:3. At optimum conditions, the performance parameters of copolymer are as follows: thermal stability was 126.0 J g−1, molecular weight was 1.28 × 107, cationic degree was 30.7%, coagulant dosage being 0.5 g kg−1, and the filter cake moisture content (CMC) and filtrate residual turbidity were 65.7% and 3.73 NTU, respectively. Based on the evaluation of the sludge dewatering process, it was found that when the coagulant dosage was 1 g kg−1, activated sludge initial pH value was 7.0, and rapid agitation speed was 120 rpm, CMC and turbidity were 63.5% and 2.95 NTU, respectively. In addition, charge neutralization and adsorption/bridging coagulation–flocculation mechanisms played an important role in sludge dewatering performance.

Preparation of a composite coagulant: Polymeric aluminum ferric sulfate (PAFS) for wastewater treatment

A new composite coagulant polymeric aluminum ferric was synthesized and parameters affecting the coagulant performance such as reaction temperature and time, and OH/Fe, P/Fe and Al/Fe molar ratios in this study, were examined. In addition, to obtain the optimum synthetic conditions resulting in the maximum turbidity removal efficiency, response surface methodology (RSM) was used to assess their interactive effects on coagulation–flocculation performance. The results showed that reaction temperature (60–80 °C) and time (30–50 min), and OH/Fe (0.1–0.3), P/Fe (0.2–0.3) and Al/Fe (1:9–1:10) molar ratios were favorable to the preparation process. The optimum synthesis conditions were reaction temperature and time, and OH/Fe, P/Fe and Al/Fe molar ratios of 80 °C, 40 min, 0.1, 0.25 and 1:10, respectively. Evaluation of the coagulation–flocculation process showed that COD (chemical oxygen demand) and turbidity removal efficiency of 82.8% and 98.2%, respectively, were achieved at coagulant dosage of 45 mg/L, wastewater initial pH of 8.5, and rapid agitation speed of 250 rpm. In addition, charge neutralization and adsorption/bridging coagulation–flocculation mechanisms played an important role in reducing the surface charge of colloids.

Effect of dosing method on color removal performance and flocculation dynamics of polyferric-organic polymer dual-coagulant in synthetic dyeing solution

Three inorganic–organic dual-coagulants were comparatively evaluated in terms of color removal, zeta potential and flocculation dynamics in treating simulative reactive and disperse dyeing wastewater. The flocculation kinetics, including floc growth rate, floc size and floc size difference in the steady-state phase, was investigated using photometric dispersion analyzer (PDA). The first dual-coagulant PFC–PDADMAC was prepared by premixing polyferric chloride (PFC) and polydimethyldiallylammonium chloride (PDADMAC) before dosing. The other two were achieved by dosing PFC and PDADMAC in different order. Results indicated that PFC–PDADMAC gave higher color removal efficiency, stronger entrapment and bridging ability, higher floc growth rate, larger floc size and wider range of floc size distribution in treating Reactive Yellow K-4G. 60.2% color removal was obtained by PFC–PDADMAC at a dosage of 30 mg/L. For the removal of Disperse Yellow RGFL, three dual-coagulants gave similar color removal rate, coagulation–flocculation mechanism, floc growth rate, floc size and floc size distribution. The maximal color removal (95.5%) was obtained by PFC–PDADMAC at a dosage of 30 mg/L.

Traitement des eaux usées par coagulation-floculation avec recirculation des boues chimiques : Performance générale et stabilité du procédé

Six series of tests were carried out to have a better understanding of the stability and efficiency of a coagulation-flocculation process with chemical sludge recycling. The tests consisted in sequential sludge recycling in 100-L pilot reactors. Other tests were performed to examine the stability following wastewater loading variations. Results showed that stability was reached immediately during the first recycling sequences. Furthermore, to obtain improved results compared with those of a classical coagulation-flocculation process, the flocculant concentration must be increased according to the sludge recycling load. Results also revealed that recycling sludge does not absorb wastewater load variations. Consequently, the implementation of sludge recycling in a wastewater treatment plant would not cause effluent degradation or entail major changes in a normal plant operation routine. The predominant coagulation-flocculation mechanisms that explained the increase in efficiency, in comparison with the classical process, were identified as enmeshment and sweep flocculation. Finally, the recycled sludge produced were conditioned and dewatered in a fashion similar to that of a classical process.Key words: recycling, sludge, preformed flocs, coagulation-flocculation, treatment, wastewater, stability.