Coagulation Conditions Research Articles

Preparation of patterned microfiltration membranes and their performance in crossflow yeast filtration

Patterned microfiltration membranes were fabricated via Phase Separation MicroFabrication (PSMF) using vapor-induced phase separation to avoid skin formation on the nonpatterned surface. A starting solution of 10% PES, 60% PEG400, 5% water and 25% NMP yielded symmetric membranes with similar pore size all throughout the cross section when 10 or 15min of vapor exposure was used before further coagulation in water. On the other hand, 5min of vapor exposure resulted in what may be called inverse asymmetric membranes, which had smaller pores on the patterned (mold) side and macrovoids throughout the cross-section. The fidelity in replicating the pattern was higher when the vapor exposure was shorter and surface area enhancements of 103% and 52% were obtained when vapor exposure times were 5 and 10min, respectively. The phase inversion rates of the polymer solutions in liquid water, humid air and humid air followed by liquid water were examined by measuring the light transmission through the solutions in time. It was observed that water in the starting solution increased the overall phase inversion rate and decreased the delay time before phase separation, in consistence with the membrane morphologies obtained with the solutions with and without water under different coagulation conditions. The patterned and nonpatterned membranes were tested in constant flux crossflow filtration of yeast suspensions at different fluxes and it was seen that the fouling rate of nonpatterned membranes was higher than patterned membranes. However, the major contribution to the improved fouling behavior appears to be the increased surface area since when the fluxes were normalized by the patterned (actual) surface area for foulant deposition, the difference between the fouling rate of patterned and nonpatterned membranes was not significant.

Coagulation performance and membrane fouling of polyferric chloride/epichlorohydrin–dimethylamine in coagulation/ultrafiltration combined process

Polyferric chloride (PFC) and epichlorohydrin–dimethylamine (DAM–ECH) with different PFC (as Fe3+)/DAM–ECH mass ratios (MR) and dose methods were used in the treatment of humic acid–kaolin (HA–kaolin) simulated water under different pH conditions. Coagulation performance, floc characteristics and membrane fouling of PFC/DAM–ECH in coagulation–ultrafiltration (C–UF) process were investigated in this study. Results showed that the optimum coagulation performance was achieved when PFC dose was 15mg/L with PFC/DAM–ECH MR of 2:1 under pH6.0. Opposite adding sequence (DAM–ECH/PFC) would reduce UV254 (ultraviolet adsorption at 254nm) and DOC (dissolved organic carbon) removal efficiency. Addition of DAM–ECH on the basis of PFC produced larger and stronger flocs with better regrowth ability. Proper dosage of DAM–ECH under certain coagulation condition could achieve the best coagulation performance and keep the UF membrane operating under a preferable status. Results of this study would be beneficial for application of composite coagulant PFC–DAM–ECH and DAM–ECH as coagulant aid in water treatment processes.

Coagulation performance and floc properties of Microcystis aeruginosa in the presence of humic acid

Coagulation removal of algae in raw water could be significantly affected by humic acid (HA). A series of jar-tests were conducted to investigate the coagulation performance with polyaluminum chloride and floc properties of Microcystis aeruginosa, a unicellular cyanobacteria, in the presence of HA. Meanwhile the coagulation mechanism was explored through the measurement of zeta potential of the supernatant. The results showed that an optimal removal efficiency of chlorophyll-a (Chl-a) was obtained at pH 8.0 with a low concentration of HA (2 mg/L) and at pH 6.0 with a high concentration of HA (8 mg/L). The floc structure was more compact and bigger-sized and the calculated fractal dimension (Df) was larger at maximum coagulation efficiency. The variation of Df was consistent with that of Chl-a removal efficiency under the same coagulation conditions. Charge neutralization was inferred to be the dominant mechanism to remove algal cells with low concentration of HA, while charge neutralization, gathering and the bridging process worked together to remove algal cells with a high concentration of HA. These results provide insight on how to achieve an optimal removal efficiency of algae in the presence of different concentrations of HA in water treatment.

Chemical coagulation process for the removal of heavy metals from water: a review

Heavy metal pollution has become one of the most urgent environmental issues, which also poses a potential threat to the human health. This article is suggested to review the advance on the performance of chemical coagulation process in removing heavy metal from water. Chemical coagulation process is considered to be a valid method which is determined by the hydrolyzed species of the inorganic coagulants under different raw water and coagulation conditions. And the main mechanisms of the removal of heavy metals are adsorption, complexation, and coprecipitation. Compared with the aluminum-based coagulants, the iron-based coagulants have better performance due to the use of wide pH range and large surface area of the resulting flocs. During the chemical coagulation process, the valence state of arsenic and antimony could affect the removal efficiency. Thus, the oxidants and reductants are often combined with inorganic coagulants used in this process. It is found that pH is an important factor greatly influencing the performance directly or indirectly. The complex resulting from the interaction between the inorganic/organic pollutant and inorganic coagulant may contribute to the removal of heavy metals. Overall, chemical coagulation is an effective way to control heavy metal pollution with/without other water treatment technologies.

곤약의 최적 응고 및 항미생물 활성을 위한 조건 확립

This study was conducted to establish optimum conditions for coagulation of konjac jelly as well as antimicrobial activity by concentration of . Hardness, gumminess, and chewiness of konjac jelly increased according to concentration of konjac powder, the key material of konjac jelly. The highest sensory evaluation score was acquired with konjac jelly made with 3% konjac powder. A concentration of 0.4-0.6% as a coagulation agent was optimum for coagulation of konjac jelly. Further, sensory score was highest at a concentration of 0.6%. All populations of bacteria, yeast, and mold in konjac jelly were restrained by in a concentration- dependent manner. Furthermore, all tested microorganisms were strictly restrained at N of .

Microfiltration of humic-rich water coagulated with cationic polymer: The effects of particle characteristics on the membrane performance

The main issue explored was the effects of different coagulation conditions on the particle characteristics that would also significantly affect the performance of membranes when filtering coagulated humic-rich water. The size distribution and morphological properties of flocs formed through the coagulation of natural organic matter (NOM) were characterized and the impact of Ca2+ on these characteristics and on the performance of the MF membrane was determined. The multi-cycle MF experiments with hydraulic wash between cycles were conducted for raw and coagulated humic-rich water, and the performance was evaluated by measuring the permeate water quality, resistance to filtration, and permeability recovery with cleaning. Coagulant (polydiallyldimethyl-ammonium chloride) additions from 50% to 100% of the charge neutralization dose substantially decreased fouling compared to when filtering raw humic-rich water. Short-term fouling was increased when 1mM Ca2+ was added, but the charge neutralization coagulation removed almost all of the fouling tendency that had occurred when filtering Ca-NOM and resulted in the highest permeability recovery. The median diameter and the two-dimensional fractal dimension of flocs produced were increased as the zeta potential reached close to zero, which resulted in the formation of a cake layer that was easily removed from the surface of the membrane.

Comparison of iron (III) and alum salt on ultrafiltration membrane fouling by alginate

Compared with humic acids or proteins, polysaccharides usually cause more severe flux decline. Here, the ultrafiltration (UF) membrane fouling caused by alginate coagulated with iron (III)/alum salt was investigated in the absence/presence of ionic strength (NaCl), calcium ions and their combinations in the system. The results showed that flux decline was significantly reduced only in the presence of high dose of iron/alum salt. With increasing ionic strength, the membrane flux caused by alginate coagulated with high dose of iron/alum salt was decreased, while that was dramatically increased in the presence of calcium ions. When ionic strength and calcium ions were presented with high dose of iron/alum salt, flux decline was determined by the ratio of sodium ions to calcium ions. Alum salt behaved much better than iron salt on reducing membrane fouling with/without ionic strength, calcium ions and their combinations in the solution. Membrane flux was high at coagulation conditions that resulted in low concentration of alginate after filtration, which was in the presence of high dose of alum salt, especially in combination of calcium ions.

RO Membrane to Remove Sulfate: an Inland Brackish Water Desalination Pilot Study

The City of Fargo completed a Facility Plan of their Water Treatment Plant (WTP) in 2011 to address two main issues: increasing water demands and high sulfate concentrations within a raw water source (Sheyenne River) primarily due to Devils Lake flooding. Reverse Osmosis (RO) was recognized as the most appropriate technology for sulfate reduction, and recommended for use in the WTP expansion. An RO pilot study was performed to evaluate its feasibility for two operational scenarios. RO membranes experienced rapid fouling in the Polishing Scenario, which used RO to further treat filtered water from the existing WTP (pretreatment, lime softening, ozone, and granular filtration). RO membranes exhibited superior performance in the Parallel Scenario, which was a separate treatment process (coagulation/flocculation/sedimentation + microfiltration/ultrafiltration +RO) parallel to the existing WTP. RO membrane autopsies indicated that membrane fouling was organic and biological for the Polishing Scenario while organic and scaling for the Parallel Scenario. Optimization studies were performed in the Parallel Scenario to determine optimal coagulation conditions for pretreatment as well as flux, recovery, and membrane cleaning regimes for both the MF/UF and the RO. Uniquely, an RO membrane selection pilot was conducted for both scenarios to evaluate RO membranes from four different manufacturers. The slight difference surface chemistry among various RO membrane can cause substantial different performance. It was found that one RO membrane could not be cleaned adequately, although it has many successful applications elsewhere. This one year pilot study proved that RO technology is feasible to reduce sulfate concentrations to acceptable levels in the City’s finished water.

The influences of coagulation conditions and storage proteins on the textural properties of soy-curd (tofu)

The contribution of storage proteins (e.g., 7S, 11S) in soybean (variety Raja Basa) on the textural properties of tofu was investigated. Applying glucono-δ-lactone (GDL) as coagulant, the protein recovery was varied, dependent on coagulant concentration (p ≤ 0.05). Different coagulants yielded different proportions of 11S/7S storage protein ratios (p ≤ 0.05). Curd coagulated with CaSO4·2H2O lacked 7S subunits. The amount of 7S was up to 8.35% of the total storage proteins. This led to increased 11S/7S storage protein ratio and consequently increased curd hardness and gumminess (23.34 and 9.10 N, respectively). An upsurge of 11S/7S storage protein ratio resulted in a higher number of covalent bonds from disulfide bonding as 11S protein contains more total cysteine groups than 7S. Conclusively, this study shows 11S/7S storage protein ratio apparently has a contribution on the textural properties of curd especially on the characteristics of hardness and gumminess.

Optimization of coagulation-flocculation parameters using a photometric dispersion analyser

Abstract. The size and structural characteristics of floc particles are important design and control parameters in water treatment and should be rapidly monitored with a reasonable amount of accuracy. In this study, a photometric dispersion analyser (PDA) coupled to standard jar test experiments was used to optimize coagulation-flocculation parameters while monitoring floc size and structure as well as the rate of floc formation during coagulation using alum. The optimal coagulation conditions were as follows: sample pH 8; alum dosage, 3 mg L−1 as Al3+; G value, 172 s−1; rapid mixing time, 20 s. These conditions resulted in unstable treated water having a calcium carbonate precipitation potential (CCPP) of −15 mg L−1 as CaCO3 and required a slaked lime dosage of 17 mg L−1 as CaCO3 to equilibrate CCPP to acceptable levels. PDA data revealed that aggregation rate and steady-state variance are primary parameters as both have substantial influence on coagulation-flocculation efficiency. However, the average steady state ratio, although an important parameter, had a lessened impact on coagulation-flocculation efficiency. The results of this study showed that the PDA instrument is an important tool in coagulation kinetic studies and can be employed as an additional tool in the optimization of coagulation conditions.

Effect of coagulant in greywater treatment for reuse: selection of optimal coagulation condition using Analytic Hierarchy Process

The objective of the present study was to (i) examine the effect of the coagulants on greywater (GW) characteristics under variable pH conditions, (ii) assess the potential of treated GW for reuse, and (iii) select optimal coagulation condition (pH and optimum dose) using Analytic Hierarchy Process (AHP). The effect of coagulants (alum and lime) was studied under four different pH conditions (8.5, 7.5, 6.5 and 5.5). Multiple linear regression models were built with optimum coagulant dose (OD) vs. pH, turbidity removal and alkalinity consumed. R2 values ranged from 0.771 to 0.852 in case of alum and from 0.778 to 0.949 in lime treatment. In alum treatment, turbidity removal was above 88%, biochemical oxygen demand removal was in the range 53–77%, and Escherichia coli removal was 95–99% under the pH conditions examined. It was observed that alum-treated GW satisfied most of the reuse standards for the discharge of effluents into land for irrigation and industrial cooling in India. Total eight alternatives were ranked using AHP, considering nine criteria/sub-criteria. Using AHP, the optimal alternative selected was alum treatment at pH 5.5 with OD 204 mg/L and the worst was lime treatment at pH 8.5.

A small point regarding DLVO coagulation conditions

Criteria for colloidal destabilization that we had imposed in earlier studies (Yeung et al., 2003 [1] and Esmaeili et al., 2012 [2]) are re-examined. Those conditions are shown here to be incorrect, but with only negligible error. We also note a minor issue with the widely-accepted condition of coagulation that is seen in almost all colloids literature.

Coagulation pretreatment of highly concentrated acrylonitrile wastewater from petrochemical plants.

Acrylonitrile (AN) wastewater is a heavily polluted and a likely hazardous liquid that is generated during the production of AN. Several chemical methods for the pretreatment of AN wastewater are available in laboratory scale. However, the harsh reaction conditions and high operational cost make these methods undesirable. Until now, four-effect evaporation is the only pretreatment method used for AN wastewater in industry despite its huge energy consumption and high cost. It is difficult to find an energy-saving pretreatment technique from the perspective of industrial application. In this study, a safe and low-cost coagulation technique was developed for the pretreatment of AN wastewater. Three types of inorganic coagulant and three types of polymer coagulant were investigated for the coagulation treatment of highly concentrated AN wastewater from petrochemical plants. The effects of coagulant type, dosage, and coagulation conditions on the pretreatment efficiency of AN wastewater were investigated. The results show that a combination of inorganic and polymer coagulants is effective for the pretreatment of AN wastewater.

Examination of the physical properties of Microcystis aeruginosa flocs produced on coagulation with metal salts

Coagulation–flocculation (C–F) is a key barrier to cyanobacterial and algal cell infiltration in water treatment plants during seasonal blooms. However, the resultant cell floc properties, in terms of size, strength and density, which dominate under different coagulation conditions and govern cell removal, are not well understood. This paper investigated the floc properties produced during C–F of the cyanobacterium, Microcystis aeruginosa, under low and high doses of aluminium sulphate and ferric chloride coagulants and at different pH values, so as to promote charge neutralisation (CN) and sweep flocculation (SF) dominant conditions (or a combination of these). It was demonstrated that application of ferric chloride produced larger flocs that resulted in higher cell removal during jar testing. These flocs were also larger than those observed for natural organic matter (NOM) and kaolin, suggesting a role of algogenic organic matter (AOM) as an inherent bioflocculant. Under SF conditions, stronger flocs were produced; however, these had lower capacity for size recovery after exposure to high shear. Analysis of particle size distribution demonstrated that large scale fragmentation followed by erosion dominated for CN while erosion dominated under SF conditions. Overall, marked differences were observed dependent on the coagulation regime imposed that have implications for improving robustness of cell removal by downstream separation processes. While the cyanobacterium, M. aeruginosa, appeared to share general floc characteristics commonly observed for NOM and kaolin flocs, there were distinct differences in terms of size and strength, which may be attributed to AOM.

Dynamic parameters of homeostasis under the influence of antiaggregant treatment in patients with atrial fibrillation and metabolic syndrome

The condition of coagulation and platelet hemostasis in 125 patients with atrial fibrillation (AF) and with metabolic syndrome (MS) has been analysed. Сoagulation and platelet hemostasis in 125 patients with AF and MS under treatment with acetylsalicylic acid (ASA) (group 1), omega-3 polyunsaturated fatty acids (omega-3 PUFAs) (group 2) and ASA with L-arginine (3 group) during 2 months were measured. It was established that omega-3 PUFAs are more effective compared with ASA/aspirin with L-arginine and it promotes normalization of fibrinogen, soluble fibrin-monomer complexes (SFMK), D-dimer and improves the platelet aggregative activity (PAA).

The characteristics of flocs and zeta potential in nano-TiO2 system under different coagulation conditions

Three coagulants were used to investigate the characteristics of flocs formed in TiO2 system, and the effects of humic acid (HA) on the coagulation process were also investigated. The results indicated that flocs could not regrow to former size in all coagulation conditions. The floc sizes after re-growth decreased with increasing the breakage period. Polyacrylamide (PAM) could significantly increase the floc size, and the fractal dimension decreased with increasing the concentration of N-PAM. Zeta potentials of flocs formed without N-PAM as coagulant decreased when the flocs were broken at 400rpm. Zeta potential using N-PAM as flocculant did not significantly change during breakage period, and this maybe caused by the adsorption of N-PAM molecules on new exposed TiO2 surfaces. The results of coagulation process using nano-Al2O3+AS as coagulant showed that nano-Al2O3 particles could increase the floc size and fractal dimension in TiO2 system, and the recovery factor was larger than only using AS. The further addition of Ca2+ and Al2O3 particles could enhance the floc size after regrowth. In the enhanced coagulation process (Al 1.0mmol/L), PACl could produce larger flocs due to electrostatic patch effects.

Use of shear wave elastography for monitoring enzymatic milk coagulation

In the manufacturing of cheese, the cutting of the curd is an essential step which depends on the firmness of the curds and significantly affects the yield of the cheese and its quality. In this work, we present a technique to measure elastic properties of the curd during coagulation that could be used to quantitatively determine the cutting time. The technique uses ultrasound to generate and measure shear waves. These waves do not propagate in liquids and their velocity of propagation depends on the viscoelastic characteristics of the medium. Hence, they can be used to identify the beginning of coagulation and subsequently to monitor the evolution of the coagulum firmness. Our results showed this technique is sensitive to changes of the medium structure during coagulation. It also proved reproducible and sensitive to different coagulation conditions. Therefore this technique can be used to develop a system suitable for the dairy industry.

Effects of different coagulants in treatment of TiO2–humic acid (HA) water and the aggregate characterization in different coagulation conditions

Effects of coagulant dosage and solution pH on the coagulation behavior of nano-Al13 were studied with respect to the treatment of TiO2–humic acid water. Polyaluminum chloride (PACl) or AS (Al2(SO4)3) and Al2O3 (100mg/L)+AS were used to compare with nano-Al13. The floc size, strength factor and fractal dimension under different coagulation conditions were investigated. The results indicated that hydrophobic NOM with larger molecular weight could be easily removed by the four coagulants. The strength factor increased with increasing the coagulant dosage for AS under all coagulation pH values. The results using PACl and nano-Al13 as coagulants indicated that the coagulant dosage had no significant effects on the strength factors. The addition of Al2O3 could significantly increase the floc size, and the fractal dimension after breakage was larger than using AS. Nano-Al13 had highest charge neutralization ability, so when the dosage was high, the removal efficiency decreased due to charge reversal. The results of the coagulation performances under three coagulation pH values indicated that nano-Al13 could re-stabilize the particles under pH 6.0 at 0.2mmol/L calculated as Al. The recovery factors using Al2O3+AS as coagulant were smaller than using AS, and this may be caused by the adsorption of HA molecules on nano-Al2O3 particles. The HA molecules in the solution could bridge the nano-particles together through bridging effects. The Al2O3 particles had positive charges on the surface under pH 6.0, and it could bridge the particles together.

Coagulation by titanium tetrachloride for fulvic acid removal: Factors influencing coagulation efficiency and floc characteristics

Coagulation efficiency of titanium tetrachloride (TiCl4) was investigated for fulvic acid (FA) (as model organic matter) removal compared to traditional coagulants — iron chloride (FeCl3) and aluminum sulfate (Al2(SO4)3). The growth, breakage and regrowth nature of flocs formed by the three coagulants were also comparatively evaluated under different coagulation conditions. Results indicated that TiCl4 achieved higher removal of UV278 (absorbance at 278nm) and DOC (dissolved organic carbon) than FeCl3 and Al2(SO4)3, and TiCl4 produced the largest flocs with the highest floc growth rate. The responses of floc to different operating parameters depend on the coagulant used, while the floc breakage and re-aggregation were also significantly influenced by shear force and break-up period. Floc strength decayed with the increasing shear force, while the inverse trend was observed for floc recoverability. An extension in break-up period resulted in the deterioration of both floc strength and recoverability regardless of the coagulants used. Flocs formed by TiCl4 displayed the weakest recoverability after breakage by contrast to conventional coagulants. Since TiCl4 is only studied recently as a novel coagulant, the comparative study of coagulation performance and floc characteristics of TiCl4 against the traditional coagulants provided valuable information for its wide application in the future.

Methotrexate Therapy in Deep Venous Thrombosis in Behcet Disease in Children

Behcet disease is a chronic condition, systemic disease, with etiopathology still incomplete known but in witch are involved immune and genetic factors who may lead to inflammation and coagulation conditions. Authors present the case of a patient, masculine sex, 14 years old, diagnosed with Behcet disease, who had the vascular manifestation, with deep and superficial lower extremity vein thrombosis, that appeared at more than five years after first signs of disease (recurrent oral ulcerations). The patient had not presented positive markers for primary thrombophilia. Methotrexate therapy led to complete disappearance of lower extremity vein thrombosis, after about one year of treatment (as shown in Doppler vascular ultrasound). No side effect was observed related to Methotrexate therapy. Conclusions: Methotrexate therapy may be a very efficient alternative treatment in deep lower extremity vein thrombosis in Behcet disease, without anticoagulants association.