Optimization of immobilized urease enzyme on porous polymer for enhancing the stability, reusability and enzymatic kinetics using response surface methodology.

The study examines the immobilization of the urease enzyme on a range of High Internal Phase Emulsion (polyHIPE) materials, assessing characteristics, efficiency, and performance. It also investigates the impact of polyHIPE type, quantity, incubation time, and various parameters on the process and enzyme activity. Surface morphology and functional groups of polyHIPE materials were determined through scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FT-IR) analyses, revealing significant alterations after modification with polyglutaraldehyde (PGA). The maximum immobilization efficiency of 95% was achieved by adding PGA to polyHIPE materials with an incubation period of 15 h. The optimized conditions for immobilized enzyme using a Box-Behnken design (BBD) of response surface methodology (RSM) were as follows: temperature (40.8 °C), pH (7.1) and NaCl concentration (0.007 g/L). Furthermore, the immobilized enzyme demonstrated remarkable reusability, retaining 75% of its initial activity after six cycles, and sustained shelf-life stability, retaining over 40% activity after 10 days at room temperature. Kinetic analyses revealed that immobilized urease exhibited higher affinity for the substrate, but lower rate of substrate conversion compared to the free enzyme. These findings offer valuable insights into optimizing urease immobilization processes and enhancing urease stability and activity, with potential applications in various fields, including biotechnology and biocatalysis.

Simultaneous production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from recovered volatile fatty acid with treatment of leachate by Pilot-Scale Mechanical Vapor Recompression.

Serious global problems faced due to many petroleum-based materials in the last century, which is called the plastic age, constitute the main motivation of this research. Considering wastewater treatment from this perspective, both the recovery of organic acids from wastewater and their conversion into bioplastics are extremely important in terms of reducing petroleum dependency. In this study, while the treatment of landfill leachate was provided with biological process integrated into Mechanical Vapor Recompression (MVR), simultaneously PHBV production was carried out with 84.9% recovered VFA as carbon source. The effects of C/N/P ratio and feeding regime on PHBV storage were investigated by Cupriavidus necator. PHBV storage of 96% (g PHBV/g DCW) was maximized by 2-stage feeding and nitrogen restriction. The ratio of 3HV to 3HB of PHBV was 45%. In addition, extracted PHBV was compared with standard PHA in terms of thermal and chemical properties with FTIR, XRD, TGA and DSC analyses.

Evaluation of volatile fatty acids and ammonia recovery approach from landfill leachate using pilot-scale mechanical vapor recompression.

Treatment of landfill leachate is still a current problem due to the high treatment costs in addition to the difficulty of meeting the discharge criteria. However, there is a more important issue that should be underlined; it is also valuable compounds that leachate contains. Conventional methods used for treatment of leachate such as membrane filtration, advanced oxidation processes, biological processes and their combinations have largely focused on treatment. However, the recovery of ammonia and volatile organic acids (VFA) in leachate is a promising approach both to overcome high treatment costs and to sustainably manage leachate. In this study, leachate treatment potential was investigated by mechanical vapor recompression (MVR) process, which offers an operational opportunity to recover high value-added products from leachate while providing an effective treatment for wastewater. Optimum operating conditions for the pilot-scale MVR process have been determined by laboratory-scale studies. VFAs were recovered as organic acid salts from the pilot-scale MVR distillate, while ammonia recovery was accomplished as ammonium sulfate from a highly contaminated concentrate stream. VFA and ammonia recovery rates were 89% and 99%, respectively. The treatment cost of leachate with MVR process was calculated according to the data obtained in pilot scale MVR studies considering the operating cost, chemical cost and economical contribution of value-added products. The results showed that the integrated MVR-crystallization process, all treatment costs are covered, with a net gain of 3.8 USD/m3. Consequently, MVR integrated crystallization process offers an economical and sustainable solution for the treatment of leachate by recovering valuable products.

Fabric dyeing wastewater treatment and salt recovery using a pilot scale system consisted of graphite electrodes based on electrooxidation and nanofiltration.

In this study, color removal, suspended solids removal, and salt recovery were investigated from different fabric dyeing wastewaters using a pilot scale treatment system. A pilot scale system was installed in the wastewater outlet area of five different textile companies. Experiments were planned for pollutant removal and salt recovery from wastewater. First, the wastewater was treated by electrooxidation (EO) using graphite electrodes. After a reaction time of 1 h, the wastewater was passed throughout the granular activated carbon (AC) coloumn. The pre-treated wastewater was passed through the membrane (NF) system to recover the salt in the wastewater. Finally, the recovered salt water was used for fabric dyeing. In the pilot scale treatment system (EO + AC + NF), 100% of suspended solids (SS) and an average of 99.37% of color were removed from fabric dyeing wastewaters. At the same time, a high amount of salt water was recovered and reused. Optimum conditions were determined as 4 V current, 1000 A power, wastewater's own pH values and 60 min of reaction time. The energy and operating cost for treatment of 1 m3 of wastewater were determined as 40.0 kWh/m3 and 2.2 US$/m3, respectively. In addition to the prevention of environmental pollution by the treatment of wastewater using the pilot-scale treatment system, the reuse of the recovered water will contribute to the protection of our valuable water resources. In addition, using the NF membrane process after the EO system, it will be possible to recover salt from wastewater with high salt content such as textile wastewater.

Novel chromatographic purification of succinic acid from whey fermentation broth by anionic exchange resins.

Replacement of the petroleum-based refineries with the biorefinery is regarded as an essential step towards a "zero" waste (circular) economy. Biobased succinic acid (SA) is listed by the United States Department of Energy among the top ten chemicals with the potential to replace chemicals from petroleum synthesis with renewable sources. Purification of bio-based succinic acid from fermentation by-products such as alcohols, formic acid, acetic acid and lactic is a major drawback of fermentative SA production. This study addresses this issue through a novel chromatographic separation using three distinct anionic resins: Amberlite IRA958 Cl (strong base anion exchange resin), Amberlite HPR 900 OH (strong base anion exchange resin) and Amberlyst A21 (week base anion exchange resin). The influence of process variables such as flow rate (0.18 BV/h, 0.42 BV/h and 0.84 BV/h), eluent concentration (1%, 5% and 10% HCl) and temperature (20, 30 and 40 °C) were investigated. The results indicated SA separation efficiency of 76.1%, 69.3% and 81.2% for Amberlyst A21, Amberlite HPR 900 OH and Amberlite IRA958 Cl, respectively. As the regenerant HCl concentration increased from 1 to 10%, calculated succinic acid separation efficiencies decreased from 80.3 to 70.7%. Notably, as the regenerant strength increased from 1 to 10%, the total amount of organic acids desorbed from the resin sharply increased. At operation temperatures of 20, 30 and 40 °C, SA separation efficacies were 81.2%, 73.9% and 76.4%, respectively. The insights from this study will be of great value in design of chromatographic separation systems for organic acids.

A hybrid process for leachate wastewater treatment: Evaporation and reverse osmosis/sequencing batch reactor.

In this study, a hybrid process for leachate wastewater treatment including evaporation and reverse osmosis (RO) membrane or biological treatment systems was suggested. Experiments were performed on a real landfill leachate wastewater. The leachate was subjected to evaporation; as a result, a distillate was obtained containing less organic matter and less substantial amounts of other pollutants, as ammonium salts and total phenols were removed. Tests were carried out at different evaporation temperatures and times. The initial leachate pH was adjusted and optimized. For optimum conditions, each of chemical oxygen demand (COD), total phenol, and ammonium salt concentrations were reduced to 99.99%, 95.00%, and 83.00%, respectively. The distillate of the first stage of the proposed process was then exposed to RO membrane system, as a first study, under different transmembrane pressure of 20, 30, and 40 bar and at different pH values of 7, 8, and 9. As a second suggested treatment system, the distillate was subjected to a biological treatment process for 30 days as a retention time, pH = 6, and room temperature 25°C ± 1°C. At the end of the research study, a comparison was conducted between results obtained with RO membrane separation and biological treatment system as two distinct treatment systems proposed for leachate landfill wastewater treatment. Although both systems were effective for landfill leachate wastewater treatment, however, with the RO membrane separation system, COD removal efficiency reached 99.99%. In the other hand, with biological treatment process, COD elimination was as much as 90.00%. Certainly, evaporation and RO are not novel ways of landfill leachate treatment; however, few studies have attempted to use similar combined system for landfill leachate wastewater treatment and attained effective results of treated water. PRACTITIONER POINTS: A hybrid process of evaporation and RO membrane or biological treatment systems was suggested for leachate wastewater treatment. For optimum conditions, COD, total phenols, and ammonium salt reductions were achieved to 99.99%, 95%, and 83%, respectively, after the first evaporation stage. The distillate of the first stage of the proposed process was then exposed to RO membrane system and biological treatment system. Different transmembrane pressure and different pH values were optimized for RO.

Optimization of the electrochemical oxidation of textile wastewater by graphite electrodes by response surface methodology and artificial neural network.

In this study, electrochemical oxidation of combed fabric dyeing wastewater was investigated using graphite electrodes. The response surface methodology (RSM) was used to design the experiments via the central composite design (CCD). The planned experiments were done to track color changes and chemical oxygen demand (COD) removal. The experimental results were used to develop optimization models using RSM and the artificial neural network (ANN) and they were compared. The developed models by the two methods were in good agreement with the experimental results. The optimum conditions were found at 150 A/m2, pH 5, and 120 min. The removal efficiencies for color and COD reached 96.6% and 77.69%, respectively. The operating cost at the optimum conditions was also estimated. The energy and the cost of 1 m3 of wastewater required 34.9 kWh and 2.58 US$, respectively. The graphite electrodes can be successfully utilized for treatment of combed fabric dyeing wastewater with reasonable cost.

Batch fermentation of succinic acid from cheese whey by Actinobacillus succinogenes under variant medium composition.

Bio-based succinic acid production has attracted global attention since its consideration as a potential replacement to petroleum-based platform chemicals. This study used three different CO2 sources, namely NaHCO3, K2CO3 and MgCO3 for fermentation of succinic acid (SA) by Actinobacillus succinogenes under three distinct substrate conditions i.e. lactose, whey and whey devoid of any supplements. Batch experiments were performed in both anaerobic flasks and 5L benchtop fermenter. SA fermentation in anaerobic flasks was unfettered by supplementary nutrients. However, fermentation in the benchtop fermenter devoid of supplementary nutrients resulted into 42% reduction in SA yield as well as lower SA productivities. Furthermore, a significant reduction of cell growth occurred in anerobic flasks at pH < 6.0, and complete termination of bacterial activity was noted at pH < 5.3. The highest SA titer, yield and productivity of 15.67 g/L, 0.54 g/g and 0.33 g/L/h, respectively, was recorded from whey fermentation with MgCO3. The present study further highlights significant inhibitory effect of K2CO3 buffered medium on Actinobacillus succinogenes. Thus, we can claim that environmental pollution as well as costs of SA production from whey can be reduced by leveraging on whey residual nutrients to support the activity of Actinobacillus succinogenes.

Efficient removal of ammoniacal nitrogen from textile printing wastewater by electro-oxidation considering the effects of NaCl and NaOCl addition.

In this study, an electro-oxidation (EO) process using graphite electrodes as electrode pairs was used for the removal of chemical oxygen demand (COD), ammoniacal nitrogen (NH4+-N), and color from real textile printing wastewater. The effects of solution pH, sodium chloride (NaCl) dosage, sodium hypochlorite (NaOCl), which is the oldest and still most important chlorine-based bleach, dosage, and oxidation time were investigated on the removal efficiencies. Operating conditions for the EO reactor were applied to current density 1 mA/cm2, distance between the electrodes: 2 cm, 150 min operation time, and stirring speed of 500 rpm. At optimum conditions: pH 9.5, applied current density 1 mA/cm2, NaCl dosage of 8 g/L, NaOCl dosage of 44.4 mg/L and 150 min electro-oxidation time, the obtained removal efficiencies were 86.5% and 91.1% for chemical oxygen demand (COD) and ammoniacal nitrogen, respectively. Efficiency was increased to 91.1% for ammoniacal nitrogen from 21.7% after applying EO combined with NaOCl addition compared to individual NaOCl addition.

Evaluation of advanced oxidation processes for the treatment of nanofiltration membrane concentrate considering toxicity and oxidation by-products.

This paper offers a feasible solution for the treatment of membrane concentrate produced from the textile industry, using the Fenton, Advanced Fenton (AF), ozonation and hydrodynamic cavitation (HC) and combination of these processes. The study investigated the optimum oxidant and catalyst concentrations, optimum operational conditions and comparison of these processes. The potential formation of chlorinated organic compounds after oxidation of membrane concentrate was also investigated by analyzing total organic halogen (TOX) and polychlorinated biphenyl (PCBs). Also, toxicity analysis was performed with Vibrio fischeri photobacteria to identify the production possibility of oxidation intermediates that are more toxic and difficult to treat than the targeted contaminants. Maximum removal efficiencies in chemical oxygen demand (COD) and color were 18.8% and 60.7% respectively using HC alone at a cavitation number (CN) of 0.1. Maximum COD, total organic carbon (TOC), and color removal efficiency at molar concentrations of 175 mM H2O2 and 35 mM Fe2+ and pH 3 after 30 min was 87.1, 80.8 and 99%. Combined HC with Fenton showed the highest removal efficiency in terms of COD, TOC, and color. It was also stated that the use of high oxidant concentrations masks the synergistic effect of HC on Fenton processes due to the scavenging effect.

A mixed integer linear programming model for long-term planning of municipal solid waste management systems: Against restricted mass balances.

Long-term planning of municipal solid waste management systems is a complex decision making problem which includes a large number of decision layers. Since all different waste treatment and disposal processes will show different responses to each municipal solid waste component, it is necessary to separately evaluate all waste components for all processes. This obligation creates an obstacle in the programming of mass balances for long-term planning of municipal solid waste management systems. The development of an ideal mixed integer linear programming model that can simultaneously respond to all essential decision layers including waste collection, process selection, waste allocation, transportation, location selection, and capacity assessment has not been made possible yet due to this important modeling obstacle. According to the current knowledge of the literature, all mixed integer linear programming studies aiming to address this obstacle so far have had to restrict many different possibilities in their mass balances. In this study, a novel mixed integer linear programming model was formulated. ALOMWASTE, the new model structure developed in this study, was built to take into consideration different process, capacity, and location possibilities that may occur in complex waste management processes at the same time. The results obtained from a case study showed the feasibility of new mixed integer linear programming model obtained in this study for the simultaneous solution of all essential decision layers in an unrestricted mass balance. The model is also able to provide significant convenience for the multi-objective optimization of financial-environmental-social costs and the solution of some uncertainty problems of decision-making tools such as life cycle assessment.

A study on near zero liquid discharge approach for the treatment of reverse osmosis membrane concentrate by electrodialysis.

A lab-scale electrodialysis (ED) which consisted of 11 pieces of cation-exchange membranes and 10 pieces of anion-exchange membranes was used to treat concentrated brine of Reverse osmosis (RO) membrane. The effect of operating parameters such as applied voltage, flowrate, and operating mode was investigated to measure the performance of a lab-scale ED. Three different voltages (5, 10, and 15 V) and flowrates (20, 30, and 40 L/h) were applied in order to optimize the operating conditions of the ED system. The maximum TDS removal efficiencies were 85%, 97%, and 98% for 5, 10, and 15 V, respectively. It was concluded that the desalination efficiencies were almost the same at flowrates values of 20, 30 and 40 L/h. The TDS concentration of the treated brine in the concentrate compartment rises to the highest value of 25,400 mg/L with desalination rate of 92.5% after five cycle operation. Moreover, the desalinated brine can be used as fresh water.

Membrane integrated process for advanced treatment of high strength Opium Alkaloid wastewaters.

In this study, an integrated aerobic membrane bioreactor (MBR)-nanofiltration (NF) system has been applied for advanced treatment of Opium processing wastewaters to comply with strict discharge limits. Aerobic MBR treatment was successfully applied to high strength industrial wastewater. In aerobic MBR treatment, a non-fouling unique slot aeration system was designed using computational fluid dynamics techniques. The MBR was used to separate treated effluent from dispersed and non-settleable biomass. Respirometric modeling using MBR sludge indicated that the biomass exhibited similar kinetic parameters to that of municipal activated sludge systems. Aerobic MBR/NF treatment reduced chemical oxygen demand (COD) from 32,000 down to 2,500 and 130 mg/L, respectively. The MBR system provided complete removal of total inorganic nitrogen; however, nearly 50 mgN/L organic nitrogen remained in the permeate. Post NF treatment after MBR permeate reduced nitrogen below 20 mgN/L, providing nearly total color removal. In addition, a 90% removal in the conductivity parameter was reached with an integrated MBR/NF system. Finally, post NF application to MBR permeate was found not to be practical at higher pH due to low flux (3-4 L/m2/hour) with low recovery rates (30-40%). As the permeate pH lowered to 5.5, 75% of NF recovery was achieved at a flux of 15 L/m2/hour.

Recovery of real dye bath wastewater using integrated membrane process: considering water recovery, membrane fouling and reuse potential of membranes.

It has been recognized by the whole world that textile industry which produce large amounts of wastewater with strong color and toxic organic compounds is a major problematical industry requiring effective treatment solutions. In this study, reverse osmosis (RO) membranes were tested on biologically treated real dye bath wastewater with and without pretreatment by nanofiltration (NF) membrane to recovery. Also membrane fouling and reuse potential of membranes were investigated by multiple filtrations. Obtained results showed that only NF is not suitable to produce enough quality to reuse the wastewater in a textile industry as process water while RO provide successfully enough permeate quality. The results recommend that integrated NF/RO membrane process is able to reduce membrane fouling and allow long-term operation for real dye bath wastewater.

Influences of electroosmosis and electrophoresis on permeate flux and membrane fouling in submerged membrane bioreactors (SMBRs).

The objective of this study was to investigate the influences of electroosmosis (EO) and electrophoresis (EP) on the permeate flux in submerged membrane bioreactors. When a polymeric membrane is placed in between an anode and a cathode, both EO and EP occur simultaneously, causing enhancement in flux. Results showed that after 150 min of filtration, the permeate fluxes were 60, 115, 175 and 260 L/m(2)/h at 0, 30, 40 and 50 V, respectively. It was shown that the EO was linearly changing with increasing voltage, reaching up to 54 L/m(2)/h at 50 V. EP was found to be a significant process in removing soluble microbial products from the membrane surface, resulting in an increase in permeate flux as the filtration progressed. About 20-fold of smaller protein and carbohydrate concentrations were found in the cake layer when the electrical field (EF) was applied. However, the EF application promoted pore fouling, because of the calcium and magnesium scaling.

Hexavalent chromium removal performance of anionic functionalized monolithic polymers: column adsorption, regeneration and modelling.

Anionic functionalized monolithic macro-porous polymers were used for the removal of hexavalent chromium(VI) anions from aqueous solution in column experiments. At a flux of 1.0 cm min and 30 mg Cr(VI) L(-1) feed concentration, breakthrough capacity and apparent capacity were 0.066 g Cr(VI) g(-1) anionic monolith and 0.144 g Cr(VI) g(-1) anionic monolith, respectively. The degree of column utilization was found to lie in the range 41-46%. Two kinetic models, theoretical and Thomas models, were applied to experimental data to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design. The simulation of the whole breakthrough curve was effective with the models. At a flux of 1.0 cm min and 30 mg Cr(VI) L(-1) feed concentration, the dispersion coefficient and adsorption equilibrium constant (K) were 3.14 × 10(-7) m s(-1) and 3,840, respectively. Also, Thomas model parameters k1 (rate constant of adsorption) and qm (equilibrium solid-phase concentration of sorbed solute) were 1.08 × 10(-3) L mg(-1) min(-1) and 0.124 g g(-1), respectively. After reaching equilibrium adsorption capacity, the monoliths were regenerated using 1 N HCl and were subsequently re-tested. It was found that the regeneration efficiency reduced from 98% after second usage to 97% after the third usage.

Biological NOx removal by denitrification process in a jet-loop bioreactor: system performance and model development.

Nitrogen monoxide (NO) and nitrogen dioxide referred as NOx are one of the most important air pollutants in the atmosphere. Biological NOx removal technologies have been developing to reach a cost-effective control method for upcoming stringent NOx emission standards. The BioDeNOx system was seen as a promising biological NOx control technology which is composed of two reactors, one for absorbing of NO in an aqueous Fe(II)EDTA2- solution and the other for subsequent reduction to N2 gas in a biological reactor by the denitrification process. In this study, instead of two discrete reactors, only one jet-loop bioreactor (JLBR) was utilized as both absorption and denitrification unit and no chelate-forming chemicals were added. In other words, the advantage of better mass transfer conditions of jet bioreactor was used instead of Fe(II)EDTA2-. The process was named as Jet-BioDeNOx. The JLBR was operated for the removal of NOx from air streams containing 500-3000 ppm NOx and the results showed that the removal efficiency was between 81% and 94%. The air to liquid flow ratio (Q(G)/Q(RAS)) varied in the range of 0.07-0.12. Mathematical modelling of the system demonstrated that the removal efficiency strongly depends on this ratio. The high mass transfer conditions prevailed in the reactor provided a competitive advantage on removing NO gas without any requirement of chelating chemicals.

Sulfonation of crosslinked styrene/divinyl benzene copolymer beads formed from porous foam and ion adsorption of copper by them: column adsorption modeling.

The porous foam is made by the polymerisation of a high internal phase emulsion and it is a highly porous, low density, open cellular material. Surface properties of the foam were chemically modified via a sulfonation process. Sulfonation added ‒SO3(‒)H(+) groups to the polymer matrix. The ion adsorption behavior of copper ions on sulfonated polymer beads, depending on inlet concentration (10-60 mg/L), pH of inlet solution (2.00-5.20) and flow velocity (1.7-11.4 m/h) was studied. It was shown that the amount of copper adsorbed was not affected with increasing concentration of feed solutions and flow velocity. Also the process was highly pH dependent. The maximum removal was 117.96 mg Cu/g dry adsorbent at flow velocity 11.4 m/h. Column experimental tests were conducted to provide data for theoretical modeling and to verify the system performance of the process. A theoretical column model adopted in this work was found to describe well the ion adsorption breakthrough characteristics.

Biodegradation characteristics and size fractionation of landfill leachate for integrated membrane treatment.

The fate of organics and nitrogen during the biological treatment with MBR and subsequent membrane filtration processes (nano filtration, NF; reverse osmosis, RO) were investigated for a landfill leachate. The chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) removal performances of membrane bioreactor (MBR) were obtained to be around 89% and 85%, respectively. The effluent COD of MBR was measured to be 1935 mg/L (30 kDa) which is much lower than experimentally determined soluble inert COD of 3200 mg/L using 0.45 µm filter. The readily and slowly biodegradable COD fractions were estimated to be 17% and 52% of raw influent COD, respectively. The respirometry based modeling test performed on raw leachate exhibited much slower degradation kinetics compared to municipal wastewater. A unique subset of model parameters was extracted from batch respirometry by using acclimated MBR sludge. The sequential ultrafiltration (UF) experiments (particle size distribution, PSD) revealed that most of the organics was below 2 nm filter mesh size. In addition, NF/RO post treatment after MBR system was required to increase COD and total nitrogen (TN) removal performances up to 99%. Relatively lower salt rejection rates around 94% was obtained for RO system as a post treatment of MBR system.

Effect of sludge retention time on membrane bio-fouling using different type and pore size of membranes in a submerged membrane bioreactor.

The objective of this study was to investigate the influence of sludge retention time (SRT) on membrane bio-fouling. An activated sludge reactor was operated at three different SRTs (10, 30, and 50 days). Submerged membrane experiments were performed when the mixed liquor suspended solids (MLSS) concentration reached the steady state conditions. MLSS concentrations reached the steady state at 3,109 ± 194, 6,209 ± 123 and 6,609 ± 280 mg/L for SRTs of 10, 30 and 50 days, respectively. The total soluble microbial products (SMP) were 20.1 ± 3.7, 16.2 ± 7.2 and 28.2 ± 8.4 mg/L at SRTs of 10, 30, and 50 days, respectively. The carbohydrate concentration in the supernatant was about two times more for SRT of 10 days than that for 50 days. The total amount of extracellular polymeric substances (EPS) extracted from the flocs were approximately 74.9 ± 11.9, 67.8 ± 15.0 and 67.5 ± 17.4 mg/g MLSS at three SRTs (10, 30, and 50 days) under the same organic loading rate. The viscosity of the biomass increased with the increasing SRT. The results of flux stepping tests showed that the membrane fouling at SRT 10 days was always higher than that of 30 and 50 days. Four different microfiltration membranes (cellulose acetate, polyethersulfone, mixed ester, and polycarbonate) with three different pore sizes (0.45, 0.22, 0.10 µm) were tested. Filtration resistances were determined for each membrane. Cake resistance was observed to be the most significant fouling mechanism for all membranes.