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This study aims to investigate the effect of using Al2O3 nanoparticles (NPs) in membrane structure on the operation condition of the membrane bioreactor. To this end, alumina NPs as the high hydrophilic agents with an approximate size of 40 nm and a concentration of 0–3 wt.% were placed within the PAN polymeric membrane matrix structure with high hydrophilicity and high mechanical resistance over the others via the phase inversion method. Characterization of synthesized nanocomposite membranes was carried out by SEM analysis. In the presence of the alumina NPs, the porosity of the membranes improved. The water contact angle measurement confirmed the superior hydrophilicity of mixed PAN membranes compared to the pure polymeric membranes. The best nanocomposite membrane with better antifouling properties was selected to evaluate the MBR's performance in wastewater treatment and assessed in terms of the resistance, flux recovery, and COD removal rates. The result of a comparison with pure membrane showed that by increasing the Al2O3 amount up to 2wt.%, irreversible fouling resistance mitigated as much as 50%. Moreover, the flux recovery ratio was increased by 15%, and the COD removal rate was also raised as large as 16%. Our investigation illustrated that the presence of alumina NPs has improved the MBR performance and decreased the irreversible fouling resistance of the membrane. [ABSTRACT FROM AUTHOR]

The aim of this study is to synthesize a magnetic nanocomposite membrane using iron oxide and alumina nanoparticles and employing it in magnetic membrane bioreactors (MBRs) for oily wastewater treatment. Al2O3 and Fe3O4 nanoparticles with approximate sizes of 20 and 30 nm respectively, were settled into a polysulfone (PSf) membrane matrix via magnetic casting method. The concentration of alumina and iron oxide nanoparticles were 0–0.25 wt% and 0.03 wt%, respectively. Compared with the blank membrane, an increase in the concentration of Fe3O4 up to 0.2 wt%, led to the flux as much as 70% and mitigated total resistance by 70%. The presence of the magnetic field around the bioreactor increased the flux significantly and reduced the cake resistance by 93%. Moreover, by applying the static magnetic field to MBR, the Chemical Oxygen Demand (COD) removal rate was increased to 93%, while in the MBR without the magnetic field the COD removal rate was 80%. Our investigation illustrated that the magnetic casting is an effective method to improve the flux and mitigate the fouling of the magnetic nanocomposite membrane. The output of this research indicates that the magnetic casting method enhance the magnetic MBRs performance for wastewater treatment. [ABSTRACT FROM AUTHOR]

The aim of this study is the synthesis of a magnetic nanocomposite membrane to reduce fouling in a magnetic membrane bioreactor. To this end, Fe 3 O 4 nanoparticles with an approximate size of 60–70 nm were settled into the polysulfone ultrafiltration membrane matrix through blending of Fe 3 O 4 nanoparticles with the dope solution. Nanocomposite membranes containing 0–0.11 wt% Fe 3 O 4 nanoparticles submerged in the magnetic bioreactor system in which the MLSS was considered between 8000–16,000 g/L and the magnetic field intensity was 40–160 mT. The results showed that an increase in the concentration of nanoparticles reduced the filtration resistance as much as 48% and developed the COD removal as much as 24% and increased the flux as large as 30%. The presence of a magnetic field around the bioreactor reduced the total filtration resistance as much as 68% and increased the COD removal as much as 34% due to the production of some changes in the membrane morphology and the sludge properties. Comparing the performance of the synthesized nanocomposite membranes with a MICRODYN-NADIR commercial membrane sample showed that magnetic nanocomposite membranes possess 30% higher flux, 27% lower filtration resistance, 41% higher COD removal compared to a commercial membrane. [ABSTRACT FROM AUTHOR]

Highlights: [•] Presence of cations in MBR removes colloids, soluble biopolymers and induces bioflocculability of activated sludge. [•] Introduction of different multivalent metallic cations is a way of fouling mitigation in MBRs. [•] Pore blocking and cake layer permeability of membrane hydraulic resistance decreased with charge density. [•] Membrane fouling was correlated to biopolymers concentration and mean flocs size of activated sludge. [Copyright &y& Elsevier]

A new mathematical model is proposed based on filtrationmechanisms for the prediction of fouling in airlift immersedmembrane bioreactors (iMBRs). The cake formation on the membrane surface through constant pressure filtration process in the iMBR was explained by a proposed cake filtration mechanism which assumes that no particle enters the pores when forming the cake layer on the membrane surface. The cake porosity reduction due to diffusion of particles was described by an intermediate blocking mechanism. Experimental study of fouling was also performed in a lab-scale airlift flat-sheet iMBR operating at constant vacuum. The mixed liquor suspended solid (MLSS) concentration was changed within the range of 5000 to 15000mg/L, while the superficial air velocity was varied between 32 and 128m³/m²/h. The presented model includes two parameters, that is, ultimate filtration resistance and initial rate of cake formation. The effect of the MLSS concentration and superficial air velocity on the parameters of the proposed model was studied. The results obtained from the model demonstrated that the ultimate filtration resistance and the initial rate of cake formation are more sensitive to the aeration rate at lower superficial velocities. It was also shown that the ultimate filtration resistance has a linear relation with MLSS concentration. A good agreement exists between the results of the model and the experimental data. The proposed model also showed a better compatibility with the experimental data compared to other fouling models available in the literature. [ABSTRACT FROM AUTHOR]

In this research, to benefit from the hydrophilic properties of zirconia nanoparticles as well as the role of iron oxide nanoparticles in improving porosity of polymer membranes simultaneously, Fe 3 O 4 @ZrO 2 /PAN nanocomposite membrane was synthesized and its performance was examined in reducing biological fouling of the membrane. FESEM analysis confirmed a size distribution of 35–55 nm, and TEM analysis confirmed a core-shell structure for Fe 3 O 4 @ZrO 2 nanoparticles. FTIR analysis identified the functional groups in the Fe 3 O 4 @ZrO 2 nanoparticles and confirmed their presence in the matrix of 1 Fe 3 O 4 @ZrO 2 /PAN NCM membrane. Contact angle analysis confirmed the role of zirconia nanoparticles in enhancing the membrane hydrophilicity by 51%, and porosimetry analysis confirmed the role of iron oxide nanoparticles in improving porosity of nanocomposite membranes by 47%. Usage of 1 wt% of Fe 3 O 4 @ZrO 2 nanoparticles in the PAN membrane matrix brought about 40% increase in water flux and 37% growth in dye rejection for 1Fe 3 O 4 @ZrO 2 /PAN NCM membrane. Investigation of the role of Fe 3 O 4 @ZrO 2 nanoparticles in the filtration of biological macromolecules indicated that 1 Fe 3 O 4 @ZrO 2 /PAN NCM membrane has 60%, 51%, and 56% less resistance to filtration of humic acid, sodium alginate, and BSA, respectively, when compared with raw membranes. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the applicability of the adsorption process for the removal of organophosphorus pesticide malathion 57% from water by using multi-walled carbon nanotubes (MWCNTs). The impact of various experimental conditions such as pH, quantity of adsorbent, concentration of pesticides, contact time and temperature was studied and optimized for the maximum removal of malathion. Unlike conventional optimization, a limited number of experiments (26 steps) were performed in a cost-effective manner for different independent variables such as MWCNTs concentration (0.1–0.5 g/L), the malathion (57%) concentration (6 mg/L and 10 mg/L), contact time (2–30 min) and pH (neutral range). Based on the experimental data obtained in a lab-scale batch study, a three-factor response surface modeling (RSM) approach was implemented in order to optimize the conditions for maximum removal of malathion, and compare experimental results with standardized malathion samples. The optimized conditions to achieve the maximum removal of malathion (100%) were determined to be a malathion concentration of 6 mg/L, an initial MWCNTs concentration of 0.5 g/L, and a contact time of 30 min. Findings of this study clearly indicated that 100% of the malathion could be cost-effectively removed by MWCNTs in conditions predicted by the proposed optimization methodology. [ABSTRACT FROM AUTHOR]

A laboratory stirred tank bioreactor with six single and dual-impeller configurations was tested to obtain the optimum operating conditions for future biological processes. Six impeller combinations consisting of three basic impeller types, namely Rushton turbine (RT), pitched 4blade (P4B) and pitched 2blade (P2B) downward flow were investigated in 1.77 L bioreactor working volume. Power consumption and gas holdup measurements were taken over a range of 100-1000 rpm of stirring speed and 1-5 Lmin-1 of air flowrates, for all the six combinations consisting of any single and dual impellers. Using predicted data some empirical correlations were derived which present relations in estimation of power consumption in stirred tanks with various impeller configurations. Electrical measurement method was use to determine the power drown in the stirred bioreactor. Gas hold-up increased with an increase in stirring speed and superficial gas velocity for all the impellers employed. The number and type of impellers in stirred bioreactor had considerable influence on gas hold-up behavior of the stirred bioreactor. Besides, Rushton turbine-dual Impeller gave comparably maximum gas hold-up, but at significantly higher power consumption levels. The proposed correlations offered good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Oxidation of glucose by homogeneous glucose oxidase was performed in rectangular bubble column reactor at 40 °C, ambient pressure and pH of 5.5 while superficial gas (oxygen) velocity was varied in the homogeneous and transition regime in the range of 0.0014-0.0112 m s-1. Effect of superficial gas (oxygen) velocity on the apparent reaction rate and its parameters was determined and it was observed that the apparent reaction rate on the basis of volume of the liquid increased with increasing the superficial gas (oxygen) velocity. The apparent reaction rate was assumed to be in the form of Michaelis-Menten equation and its apparent kinetic parameters were evaluated by the nonlinear regression method. [ABSTRACT FROM AUTHOR]

Abstract: Determinations of pertinent hydrodynamic and mass transfer parameters were carried out inside draft tube internal loop airlift bioreactor (DTAB) containing water in diesel (W/D) microemulsions with water to diesel volume ratio (φ) in the range 2.5–40%. For comparative purposes, data for diesel and water was also obtained. Increase in φ of the microemulsion systems up to 40% or increase in the amount of surfactant used to make the microemulsions resulted in a decrease in the values of ɛ g and k L a, which was attributed to the increase in the viscosity of the microemulsions. This viscosity was found to be a more suitable correlating parameter than φ. Increase in the value of φ of the W/D microemulsion resulted in a decrease in the values of liquid velocity for u gr up to 0.032m/s. At higher gas velocities, similar values were obtained for all the microemulsions. On the other hand, increase in φ of the W/D microemulsion resulted in increase in both the circulation time and mixing time values obtained inside the DTAB, although the difference was more pronounced at lower values of u gr. Suitable empirical correlations relating ɛ g , k L a, , circulation time and mixing time to riser superficial gas velocity (u gr) and kinematic viscosity were presented. The downcomer holdup data for diesel and W/D microemulsions was related to the riser holdup data using a single correlation. [Copyright &y& Elsevier]

Abstract: In an industrial fermentation of Bacillus thuringiensis, it is important to verify the intactness of bacterial plasmid content in all steps of culture. Changes in some plasmid resident properties of this bacterium could be considered as the simple potential signs of changes in the plasmid content. For studying this matter, two Cry+ (mother strain) and Cry− phenotype strains of B. thuringiensis H14 were compared. They showed different properties in many studied levels. Facing the presence of seven plasmids in the Cry+ strain only one small plasmid was observed in the Cry− strain. Despite the ability of mother strain to form aggregates (Agr+), no aggregation was observed in the Cry− phenotype (Agr−). The colony morphology of Cry+ strain was R shape while Cry− formed S shape colonies. Cry− strain grew faster than Cry+ strain, but both of them were capable to do sporulation. The protein profile using SDS-PAGE showed the presence of a 130, 65, and 25kDa Cry protein in the Cry+ strain whereas these proteins were absent in the Cry− strain. The Cry− was not toxic against Aedes aegypti and Culex pipiens larvae. [Copyright &y& Elsevier]

In this study, through a multistep enrichment and isolation procedure, a halophilic bacterial strain was isolated from unpolluted saline soil, which was able to effectively and preferentially degrade long chain alkanes (especially tetracosane and octacosane). The strain was identified by 16S rRNA gene sequence as an Alcanivorax sp. The growth of strain Est-02 was optimized at the presence of tetracosane in different NaCl concentrations, temperatures, and pH. The consumption of different heavy alkanes was also investigated. Optimal culture conditions of the strain were determined to be as follows: 10% NaCl, temperature 25-35 °C and pH 7. Alcanivorax sp. strain Est-02 was able to use a wide range of aliphatic substrates ranging from C14 to C28 with clear tendency to utilize heavy chain hydrocarbons of C24 and C28. During growth on a mixture of alkanes (C14-C28), the strain consumed 60% and 65% of tetracosane and octacosane, respectively, while only about 40% of the lower chain alkanes were degraded. This unique ability of the strain Est-02 in efficient and selective biodegradation of long chain hydrocarbons could be further exploited for remediation of wax and heavy oil contaminated soils or upgrading of heavy crude oils. Comparison of the sequence of alkane hydroxylase gene (alkB) of strain Est-02 with previously reported sequences for Alcanivorax spp. and other hydrocarbon degraders, showed a remarkable phylogenetic distance between the sequence alkB of Est-02 and other alkane-degrading bacteria. [ABSTRACT FROM AUTHOR]