Coagulation Conditions Research Articles

Influence of floc size and structure on membrane fouling in coagulation–ultrafiltration hybrid process—The role of Al 13 species

Coagulation application prior to ultrafiltration process was carried out to increase humic acid (HA) removal and membrane permeability. The [Al 13O 4(OH) 24(H 2O) 12] 7+ polycation (Al 13 species) was used in the coagulant process and polyaluminum chloride (PACl) was also used for comparison. Characteristics of aggregates pre-coagulated by Al 13 species and PACl were investigated using a laser diffraction particle sizing device. Additionally, membrane fouling was investigated under different coagulation conditions. The various resistances caused by Al 13 and PACl treatment effluents were determined using the membrane fouling index equation. The results indicated that at dose of 1 and 3 mg/L, Al 13 produced larger flocs than PACl; while when dosage further increased, the PACl-HA flocs were much larger. The flocs formed by Al 13 were strong and compact, and those formed by PACl were weak and loosely structured with the exception of the flocs generated at 1 mg/L. The investigation of membrane fouling demonstrated that Al 13 contributed to the best effluent permeating at 5 mg/L and the corresponding dose for PACl was 7 mg/L. The adsorption resistance of effluent pre-treated by Al 13 accounted for a smaller percentage of the total resistances compared with that by PACl.

VALIDATION OF A SIMPLIFIED NUMERICAL MODEL FOR HOT‐AIR TREATMENT OF EGG SHELL SURFACE

ABSTRACTThe aim of the study was to simulate a hot‐air‐based treatment of the egg shell by a simplified finite element model.The calculated temperatures were compared with experimental data observed on an egg shell instrumented with thermocouples. A simple plant was used to make eggs roll while hot and cold air jets impinged the shell on opposite sides.The results have shown good agreement between calculated and observed temperatures on the inner part of the shell, despite the simplicity of the 2D numerical model. The observed temperature profiles, compatible both with albumen coagulation condition and shell pasteurization, support the hot air treatment as a possible and innovative surface decontamination technique for table eggs.PRACTICAL APPLICATIONSAs hot‐air decontamination is an innovative one, several tests will be necessary to assess the technique and to engineer the process. Unfortunately, each trial needs a number of microbial and quality tests requiring a remarkable amount of time and money. The numerical model made possible the testing of several thermal cycles, optimizing the value of the process parameters involved, reducing experimental effort. Moreover, the 2D model enhanced the advantages, with respect to the full 3D model, balancing an acceptable feasibility loss with much shorter calculus time.

Advanced Treatment of Municipal Wastewater Effluent by Coagulation/Sedimentation and Chlorine Dioxide Disinfection

Due to increasing water scarcity, reclamation and reuse of the secondary effluent of wastewater treatment plant are widely concerned in many countries. Before reuse, the residual contaminant in the secondary effluent should be further removed to guarantee safe reuse. Coagulation/sedimentation and subsequent chlorine dioxide(ClO2) disinfection was adopted for tertiary treatment of secondary effluent. Selection of coagulant and optimization of tertiary treatment parameters were performed in this study. The results showed that coagulation could remove turbidity and total phosphours(TP) effectively. Polyaluminium chloride(PAC) was the most suitable coagulant. The optimal coagulation condition was as follows: PAC dosage of 10mg/L(measured as Al3+), reaction time of 20 min, settling time of 40 min, in this case, the average removal rate of turbidity, color, UV254, TP and TOC could reach to 58.2%, 22.8%, 18.2%, 60.6% and 22.2%, respectively. ClO2could inactive bacteria andE. colieffectively. ClO2could further remove UV254, color and TOC. In case of ClO2dosage of 5mg/L, the sterilization efficiency could reach 100%, and the removal rate of UV254, color and TOC was higher than 25%, 70% and 25%, respectively. In the optimal condition, the removal efficiency of residual contaminant by the combination process was as follows: UV254of 45.9%, color of 76.5%, TOC of 66.7%, turbidity of 61.9% and TP of 96.3%.

하수처리수 재이용을 위한 막분리 공정시 응집조건에 따른 투과효율 변화에 관한 연구

The objectives of this research are to investigate the proper coagulation conditions which are a type and doses of coagulants, mixing conditions (velocity gradients and mixing times), pH and so on through Jar-test, to evaluate the flux variations, permeate, backwashing according to characteristics of pretreatment of the wastewater by means of MF membranes for river maintenance water reuse. The effluent water from B-city K-sewage treatment plant are used for this research. Turbidity and suspended solids(SS) are 14.2 NTU and 10.4 mg/L respectively. This condition causes fouling for membrane process. The flux decline could be reduced when coagulation pretreatment was carried out. Optimal coagulations PAC which are commonly used in the sewage treatment plant was observed in this research. The results indicate that an optimal coagulation dose and pH are 80 ppm and pH of 7 respectively, but coagulation efficiency was lower at strong acid or strong base. Results showed that continuous and steady operations in membrane separation process by means of the effective removal of organic matter and turbidity with coagulation pretreatment of sewage secondary effluent were achieved.

System Optimization Coagulant Study Leads to Improved Treatment

This article discusses a pilot plant study at the Birmingham (Alabama) Water Works Board's (BWWB's) Shades Mountain Filter Plant to evaluate various coagulant doses to improve total organic carbon (TOC) removal, provide consistent floc formation, and reduce settled turbidity. The project's goal was to identify a process that out‐performed the plant's established coagulation regime, which consisted of aluminum sulfate (alum) and a coagulant aid. More than 250 coagulation conditions were tested. BWWB personnel concluded that ferric sulfate significantly improved TOC removal, provided consistent floc formation, and reduced settled turbidity. In addition, ferric sulfate worked for a wider range of raw water conditions when compared with alum. Much of the success of using ferric sulfate for TOC removal hinged on feeding 80‐100 ppm, which was possible because of high levels of raw alkalinity.

Standardization of milk using cold ultrafiltration retentates for the manufacture of Swiss cheese: Effect of altering coagulation conditions on yield and cheese quality

Fortification of cheesemilk with membrane retentates is often practiced by cheesemakers to increase yield. However, the higher casein (CN) content can alter coagulation characteristics, which may affect cheese yield and quality. The objective of this study was to evaluate the effect of using ultrafiltration (UF) retentates that were processed at low temperatures on the properties of Swiss cheese. Because of the faster clotting observed with fortified milks, we also investigated the effects of altering the coagulation conditions by reducing the renneting temperature (from 32.2 to 28.3°C) and allowing a longer renneting time before cutting (i.e., giving an extra 5min). Milks with elevated total solids (TS; ∼13.4%) were made by blending whole milk retentates (26.5% TS, 7.7% CN, 11.5% fat) obtained by cold (<7°C) UF with part skim milk (11.4% TS, 2.5% CN, 2.6% fat) to obtain milk with CN:fat ratio of approximately 0.87. Control cheeses were made from part-skim milk (11.5% TS, 2.5% CN, 2.8% fat). Three types of UF fortified cheeses were manufactured by altering the renneting temperature and renneting time: high renneting temperature=32.2°C (UFHT), low renneting temperature=28.3°C (UFLT), and a low renneting temperature (28.3°C) plus longer cutting time (+5min compared to UFLT; UFLTL). Cutting times, as selected by a Wisconsin licensed cheesemaker, were approximately 21, 31, 35, and 32min for UFHT, UFLT, UFLTL, and control milks, respectively. Storage moduli of gels at cutting were lower for the UFHT and UFLT samples compared with UFLTL or control. Yield stress values of gels from the UF-fortified milks were higher than those of control milks, and decreasing the renneting temperature reduced the yield stress values. Increasing the cutting time for the gels made from the UF-fortified milks resulted in an increase in yield stress values. Yield strain values were significantly lower in gels made from control or UFLTL milks compared with gels made from UFHT or UFLT milks. Cheese composition did not differ except for fat content, which was lower in the control compared with the UF-fortified cheeses. No residual lactose or galactose remained in the cheeses after 2 mo of ripening. Fat recoveries were similar in control, UFHT, and UFLTL but lower in UFLT cheeses. Significantly higher N recoveries were obtained in the UF-fortified cheeses compared with control cheese. Because of higher fat and CN contents, cheese yield was significantly higher in UF-fortified cheeses (∼11.0 to 11.2%) compared with control cheese (∼8.5%). A significant reduction was observed in volume of whey produced from cheese made from UF-fortified milk and in these wheys, the protein was a higher proportion of the solids. During ripening, the pH values and 12% trichloroacetic acid-soluble N levels were similar for all cheeses. No differences were observed in the sensory properties of the cheeses. The use of UF retentates improved cheese yield with no significant effect on ripening or sensory quality. The faster coagulation and gel firming can be decreased by altering the renneting conditions.

Optimization of coagulation and dissolved air flotation (DAF) treatment of semi-aerobic landfill leachate using response surface methodology (RSM)

FeCl 3 coagulation and dissolved air flotation (DAF) were combined to assess the success of these techniques for the treatment of semiaerobic landfill leachate. Treatment parameters (i.e.; flow rate, coagulant dosage, pH and injection time) were optimized via response surface methodology (RSM) using central composite design (CCD) to yield the maximum removal of turbidity, chemical oxygen demand (COD), color and ammonia nitrogen (NH 3-N). Model-determined optimum conditions were tested to confirm the predicted results. Initial concentrations of turbidity (259 FAU), COD (2010 mg/L), color (4000 PtCo) and NH 3-N (1975 mg/L) were reduced by 50%, 75%, 93% and 41%, respectively. These experimental results were consistent with those predicted by the model. The optimum operating conditions for coagulation and DAF were 599.22 mg/L of FeCl 3 at pH 4.76 followed with saturator pressure of 600 kPa, flow rate 6 L/min and injection time of 101 s.

Enhanced Coagulation for Removal of Dissolved Organic Matter and Trihalomethane Formation Potential from Raw Water Supply in Sri-Trang Reservoir, Thailand

The present research aims to examine the coagulation process enhancement for dissolved organic matter (DOM) and The present research aims to examine the coagulation process enhancement for dissolved organic matter (DOM) and trihalomethane formatation potential (THMFP) removal from a raw water supply with low turbidity and specific ultraviolet absorption (SUVA). Coagulation conditions were optimized using polyaluminum chloride (PACl), PACl with dry cationic polymer (polymer), and PACl with polymer and powder activated carbon (PAC). DOM was measured in terms of dissolved organic carbon (DOC) and ultraviolet absorption at a wavelength of 254 nm (UV-254). Results show that the optimal condition for PACl, PACl and polymer, and PACl with polymer and PAC coagulation were PACl 20 mg/L at pH 7, PACl 20 mg/L and polymer 0·1 mg/L, and PACl 20 mg/L with polymer 0·1 mg/L and PAC 10 mg/L, respectively. When the DOM contents in coagulated water were fractioned to be hydrophilic (HPI) and hydrophobic (HPO) groups, it was found that the coagulation process could effectively remove more DOC of HPO than DOC of HPI. The coagulation using PACl combined with polymer and PAC provided the highest level of DOC of HPI, DOC of HPO, Trihalomethane formation potential (THMFP) of HPI, and THMFP of HPO removal efficiencies and were shown to be 65%, 75%, 77%, and 79%, respectively.

Use Zeta Potential to Improve Direct Filtration Operation

This article discusses an optimization program that used zeta‐potential analyses to improve plant performance at the 10 ML/d (2.6 mgd) Beach Road Water Treatment Plant in Gravenhurst, Ontario, Canada. The use of zeta‐potential analyses optimized coagulant conditions to increase plant production by 50 percent.

Coagulation assessment and optimisation with a photometric dispersion analyser and organic characterisation for natural organic matter removal performance

Three South Australian source waters of low, mid and high dissolved organic carbon (DOC) levels were evaluated for coagulation efficiency in terms of natural organic matter (NOM) interaction and floc behaviour. Experiments were conducted using aluminium chlorohydrate (ACH) and aluminium sulphate (alum) at different mixing conditions with continuous monitoring of formation and breakage of flocs using a flow-through optical measurement device known as photometric dispersion analyser (PDA). A positive correlation of floc growth against coagulant dosage was found for ACH based on a limiting growth function. Floc structure was assessed by analysis of PDA derived parameters showing promise for more rapid coagulation condition optimisation than subjective visual criteria. Removal of NOM and growth of flocs are influenced more by the hydrophobicity of the NOM than the choice of coagulant. A higher hydrophobic fraction resulted in slower aggregation of flocs with both coagulants and better removal when using alum at controlled pH.

The role of endoscopy in patients with anorectal disorders

The role of endoscopy in patients with anorectal disorders

Examining Coagulation and Precoating for Seawater UF/RO System Pretreatment

Ultrafiltration (UF) is gradually becoming the technology of choice for seawater reverse osmosis (RO) pretreatment because of its ability to provide consistent, high-quality RO feed and its small footprint, among other advantages. However, because of the complexity and cost of coagulation sludge handling and disposal, coagulation as a UF pretreatment is a concern for most plant operators. Although efforts are being made to reduce or eliminate coagulation prior to UF, potential benefits may be overlooked. This study focused on the effect of coagulation conditions and modes of application on UF performance as it relates to hydraulic operation and product water quality. Coagulation was performed in two modes—inline coagulation and precoating. Filtration was performed in unstirred cells through membranes in dead-end constant pressure. UF hydraulic performance was evaluated, and UF permeate quality was characterized in terms of residual phosphate. Although precoating improved hydraulic performance, results showed that permeate quality was better when inline coagulation was applied. Furthermore, hydraulic performance for inline coagulation improved considerably when flocculation time was increased. Maximum phosphate removal was achieved in inline coagulation when pH was 6 and flocculation time was 45 min.

Generalized Minimum Variance (gmv) Control in Waterborne Wastewater Treatment

The performance of generalized minimum variance (GMV) is examined when applied to the wastewater pH control of waterborne paint production process. The control strategy is tested under batch coagulation condition on the wastewater. Al2(SO4)3 is chosen as coagulant. Ca(OH)2 is used as manipulating variable while H2SO4 is fed continuously at constant rate. The evaluated parameters of the GMV algorithm are employed precisely in the control law computation. The success of the control action is estimated using negative maximum error, the first set point reaching time, and offset. The constant offset problem is experienced with the GMV control. This offset is reduced by employing a reduction of coagulant amount.

Roles of Platelet STIM1 and Orai1 in Glycoprotein VI- and Thrombin-dependent Procoagulant Activity and Thrombus Formation

In platelets, STIM1 has been recognized as the key regulatory protein in store-operated Ca(2+) entry (SOCE) with Orai1 as principal Ca(2+) entry channel. Both proteins contribute to collagen-dependent arterial thrombosis in mice in vivo. It is unclear whether STIM2 is involved. A key platelet response relying on Ca(2+) entry is the surface exposure of phosphatidylserine (PS), which accomplishes platelet procoagulant activity. We studied this response in mouse platelets deficient in STIM1, STIM2, or Orai1. Upon high shear flow of blood over collagen, Stim1(-/-) and Orai1(-/-) platelets had greatly impaired glycoprotein (GP) VI-dependent Ca(2+) signals, and they were deficient in PS exposure and thrombus formation. In contrast, Stim2(-/-) platelets reacted normally. Upon blood flow in the presence of thrombin generation and coagulation, Ca(2+) signals of Stim1(-/-) and Orai1(-/-) platelets were partly reduced, whereas the PS exposure and formation of fibrin-rich thrombi were normalized. Washed Stim1(-/-) and Orai1(-/-) platelets were deficient in GPVI-induced PS exposure and prothrombinase activity, but not when thrombin was present as co-agonist. Markedly, SKF96365, a blocker of (receptor-operated) Ca(2+) entry, inhibited Ca(2+) and procoagulant responses even in Stim1(-/-) and Orai1(-/-) platelets. These data show for the first time that: (i) STIM1 and Orai1 jointly contribute to GPVI-induced SOCE, procoagulant activity, and thrombus formation; (ii) a compensating Ca(2+) entry pathway is effective in the additional presence of thrombin; (iii) platelets contain two mechanisms of Ca(2+) entry and PS exposure, only one relying on STIM1-Orai1 interaction.

In Vitro and Computational Thrombosis on Artificial Surfaces With Shear Stress

Implantable devices in direct contact with flowing blood are associated with the risk of thromboembolic events. This study addresses the need to improve our understanding of the thrombosis mechanism and to identify areas on artificial surfaces susceptible to thrombus deposition. Thrombus deposits on artificial blood step transitions are quantified experimentally and compared with shear stress and shear rate distributions using computational fluid dynamics (CFD) models. Larger steps, and negative (expanding) steps result in larger thrombus deposits. Fitting CFD results to experimental deposit locations reveals a specific shear stress threshold of 0.41 Pa or a shear rate threshold of 54 s(-1) using a shear thinning blood viscosity model. Thrombosis will occur below this threshold, which is specific to solvent-polished polycarbonate surfaces under in vitro coagulation conditions with activated clotting time levels of 200-220 s. The experimental and computational models are valuable tools for thrombosis prediction and assessment that may be used before proceeding to clinical trials and to better understand existing clinical problems with thrombosis.

Combining Coagulation Process with Biological Pretreatment for APMP Effluents Treatment

The moderate pollution load of APMP effluents provides a chance for a new treatment process--combination of biological pre-treatment and coagulation treatment. Biological pre-treatment can reduce the pollution load and produce biomass at the same time. The removal of COD was 60.22% and the yield of biomass was 7.12g/L at the optimized conditions treated by Aspergillus niger. And the removal of acid-soluble lignin and color were up to 60% and 42.57%. The coagulation treatment was applied after bio-treatment by using alum and PAM as coagulation agent. The conditions of coagulation were optimized in this article. The optimized conditions were: Dosages of alum and PAM were 1000-1200mg/L and 2mg/L, pH is 5, stirring time is 30S at 300rpm, the temperature is 50°C. The coagulation removals of COD, color and turbidity were 83.80%, 86.38% and 98.33%. The removals of color were characterized by absorbance of 465nm, 325nm, 275nm and 254nm.

Employing the Taguchi method to obtain the optimum conditions of coagulation–flocculation process in tannery wastewater treatment

In this study a series of jar test experiments, designed using Taguchi method, were carried out to determine the optimum conditions for tannery wastewater treatment, and the effects of type and dose of coagulant, type and dose of coagulant aid and pH on the efficiency of coagulation–flocculation process were evaluated. The goal parameters to find the optimum conditions were each of chemical oxygen demand (COD), chromium concentration, total dissolved solids (TDS) and turbidity of the wastewater, or all together, which were used to track the efficiency of the treatment process. Coagulant type in COD removal, pH in chromium removal, coagulant aid type in TDS removal and coagulant aid dose in turbidity removal were the most effective factors. The optimum conditions that were obtained for the treatment of the wastewater were: 800 ppm FeCl 3 as coagulant, 600 ppm Na 2CO 3 as coagulant aid and pH 7.5 for COD removal; 1600 ppm FeCl 3 as coagulant, 100 ppm CaO as coagulant aid and pH 7.5 for chromium removal; 1600 ppm FeCl 3 as coagulant, pH 9 and 300 ppm Na 2SiO 3 as coagulant aid for TDS removal; and 800 ppm PAC (polyaluminum chloride) as coagulant, pH 7.5 and 600 ppm Na 2CO 3 as coagulant aid for turbidity removal. The optimum conditions found for COD removal, were selected as optimum conditions for the cases where the removal of aforementioned parameters, all together, is treatment goal.

Study on the Mass Transfer Process in Pan Wet-Spinning

In order to reveal the formation mechanism in PAN wet-spinning process, the Magnifying Method was used to determine the mass transfer rate difference between solvent and coagulant by measuring the weight loss percent of the spinning dope at different interval in the coagulation bath. Then the effect of coagulation condition on and on structure and properties of as-spun fibers was discussed. It was found that increased along with hoist of the molecular volume of coagulants or the coagulation bath temperature but decreased with the increase of the dope solid content or coagulation bath concentration. When the coagulation condition was very moderate（high solid content, low bath temperature or high bath concentration）, the was smaller, the counter-diffusion took place slowly and peacefully, and sequentially an even and compact meshwork microstructure was obtained, thus the density and breaking tenacity of as-spun fibers increased gradually.

Effect of aggregate characteristics under different coagulation mechanisms on microfiltration membrane fouling

Effect of particle charge, size and fractal dimension under different pre-coagulation pHs and alum dosages on microfiltration (MF) membrane permeability and removal of humic acids (HAs) were studied. Both aggregates structure and size played important roles in membrane filtration. Under sweep coagulation condition, the insufficient low coagulant dosage of 10 mg/L alum resulted in low removal of HAs and the occurrence of serious membrane pore blocking by some small flocs with size corresponding to membrane pores. However with alum overdosing, the cake layer resistance increased by the direct fouling load from alum hydrolysis Al(OH) 3. Under complexation-charge neutralization coagulation, aggregates with low fractal dimension of loose structure improved permeate flux predominately when particles were near isoelectric point with alum dosages of 20 and 40 mg/L. When alum increased to 60 mg/L and above, although the flocs fractal was much lower, the MF membrane permeability deteriorated severely because more small particles produce higher cake layer specific resistance as a result of a great charge repulsion force. Under the optimum pre-coagulation alum dosages of 20 and 40 mg/L, the membrane fouling was much more alleviative at pH 5 than pH 7 because the more loose aggregates formed under charge neutralization coagulation than sweep coagulation.

Coagulation Condition Effects on the Structures and Properties of Dihydroxy Poly(P-phenylene Benzobisoxazole) (DHPBO) Nascent Fibers Prepared by Dry-Jet Wet-Spinning Process

The effect of coagulation conditions [coagulation bath temperature (T cb), coagulation bath water concentration (C cb), and air gap distance (D ag)] during the dry-jet wet-spinning process on the surface morphology, microstructures, and mechanical properties of dihydroxy poly(p-phenylene benzobisoxazole) (DHPBO) nascent fibers was investigated. The coagulation bath system was polyphosphoric acid (PPA)/H2O and the stretch ratio was kept as 1.7. The crystal characteristics, microstructures, and mechanical properties of the DHPBO nascent fibers were characterized by XRD, SEM, and single-fiber tensile testing. The results indicate that when the T cb was 25°C, C cb was 10% and D ag was 30 cm, DHPBO nascent fibers with fine crystallites, circular and smooth morphology, and excellent mechanical properties can be achieved.