Coagulation Conditions Research Articles

Study on Kinetics of Coagulant Polysilicate Aluminium Ferric Magnesium in Coagulation Process

With poly aluminum ferric silicate (II) and magnesium (PSAFMS) coagulation treatment of four kinds of reactive dyes, through the determination of its absorbance with coagulation time changes, studied the coagulation reaction kinetics problems, as PSAFMS coagulant development would lay the theoretical foundation of application. Under coagulation condition that the water temperature was 8°C, pH=11, PSAFMS coagulant dosage was 10 ml/L, in 3 minutes the decolorization rate of reactive red RSB was 94.6%, reactive blue 3GF was 93.3%, reactive navy blue S-G was 80.8% and reactive yellow M-3RE was 75%. Different reactive dye decolorization rate is differences. It is related to dye molecular structure and particle size of the radius. From ln(0/t)-t, (1/0-1/t)-t relation curve of the linear correlation coefficient, the first-order reaction of the linear correlation coefficient than the secondary correlation coefficient was better, and more than 0.9668, so PSAFMS coagulant with reactive dye decolorization reaction is the first-order. The rate equations for the ln(0/t) = kt, just different reactive dye has different reaction rate constant. .

Comparison of coagulant type on natural organic matter removal using equimolar concentrations

Research has shown that in drinking water sources there is a portion of the natural organic matter (NOM) that is recalcitrant to coagulation, regardless of the treatment conditions applied. Advances in inorganic coagulants have resulted in the emergence of many pre-polymerized formulations which may demonstrate improved coagulation performance. The aim of this study was to determine the effects of several coagulant types on dissolved organic carbon (DOC) removal where the molar concentrations of the metal ions were comparable. In the second stage, this work also investigated selected coagulants to determine whether improvements in coagulation conditions or alternative coagulants will be sufficient to remove problematic components in the organic matter responsible for disinfection demand and disinfection by-product (DBP) formation in a high DOC water source. When compared at equimolar concentrations, advanced coagulants were found to perform equally for DOC removal as traditional inorganic coagulants. While they did not necessarily target or improve removal of recalcitrant NOM and DBP precursors, they successfully demonstrated broader conditions at which coagulation was effective, reducing the reliance on precise optimization strategies. Coagulation remains a well developed and cost effective means of water treatment, with continuing relevance into the foreseeable future.

Preparation and Characterization of Novel Hollow Fiber Membrane with Multicomponent Polymeric Materials

Poly(vinylidene fluoride)(PVDF), poly(vinyl chloride)(PVC), and poly(methyl methacrylate)(PMMA) were used as the main materials in the preparation of novel blend five-hole membrane. Dimethylacetamide (DMAC) and polyvinyl pyrrolidone (PVP) were used as solvent and additive, respectively. The effect of some external coagulation conditions on the property of five-hole membrane was studied. The external coagulation conditions investigated in the work were the coagulation temperature and the DMAC content in coagulation bath. The result showed that the flux increased along with the increase of coagulation bath temperature and could reach the max at 35°C, then decreased gradually. The effect of the DMAC content in coagulation bath on flux is very similar to that of the temperature. The cross-sectional structures were examined by scanning electron microscopy.

Optimization of Magnetic Coagulation Process for River Water Treatment Using the Response Surface Method

Response surface methodology (RSM) was applied to optimize the magnetic coagulation conditions for micro-polluted river water treatment. Based on single-factor experiment, Box-Behnken central composition experiment design was applied. The poly aluminum Chloride (PAC), magnetic particle, polyacrylamide (PAM), mixing stirring and flocculating stirring revolving speed were chosen as causal factors. RSM was employed to study the effects of these factors on the turbidity removal efficiency. Base on the target value (>95%), the results show that the optimum conditions were PAC 29.31mgL-1, magnetic particle 61.90mgL-1, PAM 0.48mgL-1, mixing stirring revolving speed 288rpm, flocculating stirring revolving speed 6 rpm. The average turbidity removal efficiency in three validation experiments was 95.36%, with the predicted value was 95.19%. The relative error between the measured data and the predicted value was 0.17%. It confirms that RSM was a useful tool to optimize the magnetic coagulation operating conditions for micro-polluted river water treatment.

Effect of shear conditions on floc properties and membrane fouling in coagulation/ultrafiltration hybrid process—The significance of Alb species

Impacts of increased shear during coagulation on ultrafiltration permeate flux in coagulation–ultrafiltration (C–UF) hybrid process were investigated in this study. Three Al-based coagulants, alum, PACl and PACl–Alb, were applied to explore the role of Alb species in the C–UF process. Floc characteristics, including floc size, strength, re-formation ability and fractal structure under different coagulation conditions, were studied using a laser diffraction particle sizing device. Additionally, resistance analyses were conducted to investigate the membrane fouling mechanisms. The results indicated that alum generated the largest flocs with loosely bonded structures before breakage, which were, however, the weakest and with poor re-growth abilities. PACl–Alb contributed to the strongest flocs with the best re-growth abilities and the highest compact degree. The results of ultrafiltration experiments showed that for conventional coagulation without breakage, alum led to a flux reduction of 34%, while the reduction for PACl and PACl–Alb was 39% and 49% respectively. However, under the increasing breaking shears, the adsorption and cake layer resistances for alum coagulation increased and fluxes were markedly aggravated; PACl–Alb coagulation effluent displayed the least resistances and flux variations. An extension in breakage time led to much severer flux decline than short breakage period. PACl–Alb led to the smallest changes in flux declines.

The lysis of Microcystis aeruginosa in AlCl3 coagulation and sedimentation processes

The membrane integrity of cells is significant for the safe and effective removal of cyanobacterial cells from drinking water sources. In this paper, cell density counting, cell viability testing, chlorophyll-a determination, extracellular MC-LR monitoring and PCR–DGGE analysis were applied to assess the effects of coagulant dose, shear and floc storage time on the integrity of Microcystis aeruginosa FACHB-905. Results showed that all cells were removed without damage to membrane integrity under the optimum coagulation conditions: coagulant dose 15mg/L AlCl3, rapid mix speed 250r/min, rapid mix time 1min, slow mix speed 20r/min, slow mix time 20min. The coagulant dose and shear did not cause the lysis of cells and ensuing release of MC-LR. But when the flocs were stacked over 6days, the cells lysed and the MC-LR concentration increased above the background level. In addition, the degree of cell breakage without coagulation was higher than the coagulated cells in flocs. Therefore, keeping the flocs safely treated or disposed of on time as well as keeping the cyanobacterial cells integrally removed plays an important part in controlling the harm of blooms to drinking water production.

Physicochemical design of the morphology and ultrastructure of cellulose beads

Cellulose was dissolved in NaOH–urea–water and beads were prepared by coagulation into nitric acid as well as saline solution. Morphology and ultrastructure of the beads were modified by controlling the molarity of the acid (0–10M) and temperature (5–50°C) of the coagulation media and the cellulose concentration (3–7%). The beads were characterized by optical image analysis (shape, volume, and size distribution) and weight (total porosity). Cross-sections of CO2 critical point dried beads were studied by field emission scanning electron microscopy (FE-SEM) and specific surface areas of 336–470m2g−1 were determined from nitrogen adsorption isoterms. Pore size distribution was analyzed using solute exclusion technique. Our results demonstrate that the ultrastructure can be controlled by alteration of the coagulation conditions. Changes in size, shape and surface area were substential. Also generation of micro- (⩽2Å), meso-, or macropores (⩾50Å) can be favored.

Optimizing the coagulation process in a drinking water treatment plant – comparison between traditional and statistical experimental design jar tests

In this study of coagulation operation, a comparison was made between the optimum jar test values for pH, coagulant and coagulant aid obtained from traditional methods (an adjusted one-factor-at-a-time (OFAT) method) and with central composite design (the standard design of response surface methodology (RSM)). Alum (coagulant) and polymer (coagulant aid) were used to treat a water source with very low pH and high aluminium concentration at Sri-Gading water treatment plant (WTP) Malaysia. The optimum conditions for these factors were chosen when the final turbidity, pH after coagulation and residual aluminium were within 0-5 NTU, 6.5-7.5 and 0-0.20 mg/l respectively. Traditional and RSM jar tests were conducted to find their respective optimum coagulation conditions. It was observed that the optimum dose for alum obtained through the traditional method was 12 mg/l, while the value for polymer was set constant at 0.020 mg/l. Through RSM optimization, the optimum dose for alum was 7 mg/l and for polymer was 0.004 mg/l. Optimum pH for the coagulation operation obtained through traditional methods and RSM was 7.6. The final turbidity, pH after coagulation and residual aluminium recorded were all within acceptable limits. The RSM method was demonstrated to be an appropriate approach for the optimization and was validated by a further test.

Development of Coagulation Factor Probes for the Identification of Procoagulant Circulating Tumor Cells

Metastatic cancer is associated with a hypercoagulable state, and pathological venous thromboembolic disease is a significant source of morbidity and the second leading cause of death in patients with cancer. Here we aimed to develop a novel labeling strategy to detect and quantify procoagulant circulating tumor cells (CTCs) from patients with metastatic cancer. We hypothesize that the enumeration of procoagulant CTCs may be prognostic for the development of venous thrombosis in patients with cancer. Our approach is based on the observation that cancer cells are capable of initiating and facilitating cell-mediated coagulation in vitro, whereby activated coagulation factor complexes assemble upon cancer cell membrane surfaces. Binding of fluorescently labeled, active site-inhibited coagulation factors VIIa, Xa, and IIa to the metastatic breast cancer cell line, MDA-MB-231, non-metastatic colorectal cell line, SW480, or metastatic colorectal cell line, SW620, was characterized in a purified system, in anticoagulated blood and plasma, and in plasma under conditions of coagulation. We conclude that a CTC labeling strategy that utilizes coagulation factor-based fluorescent probes may provide a functional assessment of the procoagulant potential of CTCs, and that this strategy is amenable to current CTC detection platforms.

In-line coagulation prior to ceramic microfiltration for surface water treatment—minimisation of flocculation pre-treatment

Abstract In-line coagulation/flocculation with subsequent low pressure ceramic membrane filtration has emerged during the last years as a treatment alternative for surface waters with high natural organic matter (NOM) content and low turbidity. In such a hybrid process, the requirements on the flocculation step may significantly differ, if compared to treatment schemes where for example rapid filters are used instead of a membrane. Thus, process performance, expressed as DOC and colour removal, membrane fouling and residual metal concentration, was investigated in dependence on the coagulant dosage, flocculation time and shear, while all other coagulation conditions were kept constant. Minimum flocculation requirements were established. A synthetic surface water (DOC 6.8 mg C l−1, colour 55 mg Pt l−1) was treated by rapid inline coagulation with Polyaluminium chloride (PACl), at Al-dosages of 2.6 and 4.4 mg l−1 and a coagulation pH of 6, followed by inline flocculation at varying conditions (G-values: 4–3...

Design of experiments for Malachite Green dye removal from wastewater using thermolysis – coagulation–flocculation

Abstract Thermolysis – coagulation–flocculation was used for reduction of colour and chemical oxygen demand (COD) of aqueous basic dye Malachite Green. Statistical design of experiment was used for thermolysis experiments which resulted of 69.57% and 70.59% maximum reduction of COD and color, respectively at the optimum conditions of 95 min treatment time, 82°C treatment temperature, and pH 11.02. MgCl2 was used as coagulant for coagulation–flocculation. About 98% of color and 90% of COD were reduced at a final pH of 10.89 and a coagulant dose of 3 g MgCl2 l−1 of dye solution. The optimum conditions for coagulation–flocculation process were determined by varying a single factor while keeping other factors fixed at a specific set of conditions. Coagulation–flocculation after thermolysis at the optimal operating conditions resulted in a reduction of 91.26% COD and 98.78% color at final pH 10.89 but at a much lesser coagulant dosage of 500 mg l−1. Compared to only coagulation–flocculation, combined process of thermolysis followed by coagulation–flocculation produced relatively less floc, since lesser amount of coagulant was required to remove higher color and COD.

Advanced treatment of the output-stream of biological leachate treatment by appropriate combination of coagulation/flocculation and oxidation

An integrated technique consisting of oxidation and coagulation-flocculation processes was investigated in order to provide an effective method for the treatment of biologically pre-treated leachate and to reduce pollutants to values under the limit required for discharging to the receiving waters. Leachate containing 985 mg L(-1) chemical oxygen demand (COD) was treated by using oxidation with NaClO, coagulation/flocculation with aluminium sulfate (alum) or poly-ferric sulfate (PFS) as well as combined pre-oxidation followed by coagulation/flocculation. Oxidation resulted in the removal of COD and colour up to 78.9 and 88.4%, respectively, however residual COD values were over 200 mg L(-1) even under intensive experimental conditions (high dosage of NaClO and prolonged oxidation time). Coagulation with PFS was found to be more efficient in comparison with alum, and it yielded a residual COD of 184 mg L(-1) the optimum coagulation conditions (polyacrylamide (PAM) 5 mg L(-1), PFS 30 mg L(-1), pH 6, reaction time 20 min). The combined process involving oxidation followed by coagulation/flocculation with PFS resulted in residual COD values lower than 100 mg L(-1) the following conditions: 40-60 min pre-oxidation with 30 mg L(-1) NaClO followed by coagulation with 200-250 mg L(-1). Hence, pre-oxidation with NaClO followed by coagulation with PFS was recommended for removal of biologically-treated substances from the biologically-treated or stabilized leachate.

Membrane flux dynamics in the submerged ultrafiltration hybrid treatment process during particle and natural organic matter removal

Particles and natural organic matter (NOM) are two major concerns in surface water, which greatly influence the membrane filtration process. The objective of this article is to investigate the effect of particles, NOM and their interaction on the submerged ultrafiltration (UF) membrane flux under conditions of solo UF and coagulation and PAC adsorption as the pretreatment of UF. Particles, NOM and their mixture were spiked in tap water to simulate raw water. Exponential relationship, ( J P/ J P0 = a×exp{–k[t–( n–1) T]}), was developed to quantify the normalized membrane flux dynamics during the filtration period and fitted the results well. In this equation, coefficient a was determined by the value of J P/ J P0 at the beginning of a filtration cycle, reflecting the flux recovery after backwashing, that is, the irreversible fouling. The coefficient k reflected the trend of flux dynamics. Integrated total permeability (Σ J P) in one filtration period could be used as a quantified indicator for comparison of different hybrid membrane processes or under different scenarios. According to the results, there was an additive effect on membrane flux by NOM and particles during solo UF process. This additive fouling could be alleviated by coagulation pretreatment since particles helped the formation of flocs with coagulant, which further delayed the decrease of membrane flux and benefited flux recovery by backwashing. The addition of PAC also increased membrane flux by adsorbing NOM and improved flux recovery through backwashing.

The Depth of Phosphorus Removal by Three Coagulations

Using the secondary settling tank effluent, this paper is going to research the potentials of three coagulations (polyaluminium chloride, ferric sulfate, and self-polymeric aluminum ferric) in deep chemical phosphorus removal by the beaker experiment. The experiment focuses on the dosages, the hydraulic conditions of coagulation and effect of pH on the removal. The results show that three coagulants have good efficiencies in phosphorus removal. After coagulant treatments, phosphorus can be decreased below 0.5mg/L and achieve Grade A standards of urban sewage treatment plants (GB18918-2002). The removal efficiencies of polymer silicate are superior to those of poly aluminum chloride and polymeric ferric sulfate.

Treatment of biologically treated leachate by oxidation and coagulation

This work aims to investigate removal efficiency of oxidation and coagulation/flocculation processes, to provide an effective method for the treatment of biologically pre-treated leachate. Leachate containing 985 mg L(-1) COD was treated by using three treatment schemes, i.e. oxidation, coagulation/flocculation and the combined process of coagulation/flocculation followed by oxidation. The application of single oxidation resulted in the effective removal of COD and color up to 80.4 and 83.2%, respectively. However, residual COD values lower than 200 mg L(-1) could only be achieved under intensive experimental conditions (high dosage of Ca(ClO)(2) and prolonged oxidation time). Coagulation/flocculation yielded residual COD values higher than 200 mg L(-1) even at the optimum coagulation conditions. The combined treatment by coagulation/flocculation followed by oxidation yielded final COD lower than 100 mg L(-1) at the following conditions: pre-coagulation with 250 mg L(-1) PFS (poly-ferric sulfate) and over 30-min post-oxidation, or pre-coagulation with 300 mg L(-1) PFS and over 20-min post-oxidation. Hence, pre-coagulation with PFS followed by oxidation with Ca(ClO)(2) was recommended for advanced treatment of biologically treated leachate.

Using magnetic seeds to improve the aggregation and precipitation of nanoparticles from backside grinding wastewater

Backside grinding (BG) wastewater treatment typically requires large quantities of chemicals, i.e. polyaluminum chloride (PAC) coagulant and produces considerable amounts of sludge, increasing the loading and cost of subsequent sludge treatment and disposal processes. This study investigated the effects of the addition of magnetic seeds (FeO*Fe 2O 3) of selected particle sizes and of optimized combinations of magnetic seeds and PAC on the aggregation of silica nanoparticles from BG wastewater and on the sedimentation time at various pH values (5–9). The results show that the turbidity of BG wastewater was significantly reduced by the magnetic aggregation treatment. The dosage of PAC combined with 2.49 g L −1 or 1.24 g L −1 of magnetic seeds was reduced by 83% (from 60 to 10 mg L −1) compared to the conventional process of using only PAC as a coagulant. The turbidity of the BG wastewater, initially 1900–2500 NTU, could also be successfully decreased about to 23 NTU by the addition of 3.74 g L −1 magnetite (FeO*Fe 2O 3) only at pH 5 with an applied magnetic field of 1000 G. Different coagulation conditions using magnetic seeds combined with coagulant resulted in different aggregation performances. The treatment performance was more effective by using two-stage dosing, in which magnetic seeds and PAC were added separately, than that with one-stage dosing, where the magnetic seeds and PAC were added simultaneously during rapid mixing. The two-stage dosing allowed for a reduction in the optimum dosage of magnetic seeds from 3.74 g L −1 to 2.49 g L −1 or 1.24 g L −1 without affecting performance when coupled with 0.01 g L −1 of PAC coagulant. The developed method effectively reduced the production of waste sludge.

The effect of different types of micro‐bubbles on the performance of the coagulation flotation process for coke waste‐water

AbstractBACKGROUND: Comparison experiments were carried out with three kinds of micro‐bubbles on the coagulation flotation process treatment of coke waste‐water under optimum coagulation conditions obtained from zeta potential measurement.RESULTS: Micro‐bubble flotation with ozone showed the best performance. The ozone micro‐bubbles exhibited high absolute zeta potential values, creating repulsion forces thus avoiding the coalescence of bubbles as well as creating attractive interaction between bubbles and particles in the waste‐water. Moreover, the fluorescence intensity of three micro‐bubble samples showed that the ozone micro‐bubble system produced the most hydroxyl radicals, which contributed to the degradation of organic material in the coke waste‐water. Compared with either air micro‐bubble flotation and oxygen micro‐bubble flotation processes, pyridine removal efficiency of the ozone micro‐bubble flotation process was, respectively, 4.5 and 1.7 times higher, and benzene removal efficiency 3.6 and 1.5 times higher. Finally, drainage models and oxygen diffusion models of the three kinds of micro‐bubble water samples verified the long persistence of the three kinds of micro‐bubbles in the water.CONCLUSION: The application of ozone micro‐bubble technology in coagulation processes may provide an efficient and cost‐effective approach to the treatment of waste‐water containing refractory organic compounds. Copyright © 2011 Society of Chemical Industry

Morphological architecture of dual-layer hollow fiber for membrane distillation with higher desalination performance

A new strategy to enhance the desalination performance of polyvinylidene fluoride (PVDF) hollow fiber membrane for membrane distillation (MD) via architecture of morphological characteristics is explored in this study. It is proposed that a dual-layer hollow fiber consisting of a fully finger-like macrovoid inner-layer and a sponge-like outer-layer may effectively enhance the permeation flux while maintaining the wetting resistance. Dual-layer fibers with the proposed morphology have been fabricated by the dry-jet wet spinning process via careful choice of dopes composition and coagulation conditions. In addition to high energy efficiency ( EE) of 94%, a superior flux of 98.6 L m −2 h −1 is obtained during the direct contact membrane distillation (DCMD) desalination experiments. Moreover, the liquid entry pressure ( LEP) and long-term DCMD performance test show high wetting resistance and long-term stability. Mathematical modeling has been conducted to investigate the membrane mass transfer properties in terms of temperature profile and apparent diffusivity of the membranes. It is concluded that the enhancement in permeation flux arises from the coupling effect of two mechanisms; namely, a higher driving force and a lower mass transfer resistance, while the later is the major contribution. This work provides an insight on MD fundamentals and strategy to tailor making ideal membranes for DCMD application in desalination industry.

Removal of natural organic matter (NOM) by the coagulation–ultrafiltration system using an inorganic–organic composite coagulant

A coagulation–ultrafiltration system to treat drinking water has been widely studied. This study investigated the feasibility and potential of using inorganic-organic composite coagulant in the coagulation-ultrafiltration system for natural organic matter (NOM) removal. The removal efficiency and membrane fouling were studied at different coagulation conditions. And in order to observe how inorganic-organic composite coagulant affects the permeate flux, a resistance analysis was conducted. The results suggest that although the treated water quality in a composite coagulant system was not improved significantly, composite coagulant was more advantageous in terms of improving the permeate flux of the coagulation–ultrafiltration system than inorganic coagulant by reducing the resistance due to cake formation and adsorption. The coagulation conditions of composite coagulant are important for the performance of the coagulation–ultrafiltration system. When dosage is 3 mg L–1 and pH is 6, the removal efficiency and the permeate flux are the highest in our study.

Micellar synthesis and characterization of ultrafine silver powders

We have developed methods for the synthesis and coagulation of ultrafine silver powders in the water-Triton N-42-decane inverted-micellar system. Varying AgNO3 concentration (1–5 mol/L), the type of reducing agent (hydrazine or potassium borohydride), and the coagulation method (spontaneous or induced by acetone or water addition) allowed us to select the parameters that provide powders containing about 98% silver and having particle sizes of 15–80 nm. We propose methodology for characterizing ultrafine silver powders comprising the determination of the total and surface composition and the charge state of impurities using atomic absorption spectroscopy (AAS), atomic emission spectroscopy (AES), microanalysis, FTIR spectroscopy, and X-ray photoelectron spectroscopy. The impurity composition of the nanomaterial is found to depend on the type of reducing agent, the synthesis parameters, and coagulation conditions.