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The main purpose of this research is to use aluminum oxide nanoparticles in order to manipulate the formation mechanism of poly acrylonitrile (PAN) UF membranes with the aim of improving their performance in separating biological macromolecules including sodium alginate, humic acid, bovine serum albumin (BSA). For this purpose, alumina nanoparticles with the approximate size of 40 nm and high hydrophilicity properties were placed within the structure of the PAN membrane to engineering design of pores. Viscometry analysis and determination of cloud point were performed in order to investigate the formation mechanism of the nanocomposite membrane. Chemical, surface, and morphological variations of the nanocomposite membrane were evaluated using FTIR, zeta potential, contact angle, DLS, porosity metering, SEM, and AFM analyses. Eventually, investigation of the filtration performance of the nanocomposite membranes showed that the membranes containing 1 wt% of alumina nanoparticles have a water flux 57% more than that of raw membrane. Further, in terms of flux recovery parameter, this membrane indicated 22, 9, and 14% increase for sodium alginate, humic acid, and BSA, respectively. Regarding extent of dye separation, sodium alginate separation, humic acid separation, and BSA separation, 12, 7, 9, and 7% increase was observed for the nanocomposite membrane containing 3 wt% of alumina nanoparticles. [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]

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]

Bubble size distribution was modelled by employing the population balance equation (PBE). All three bubble coalescence mechanisms (turbulence, buoyancy and laminar shear) and the main bubble breakup mechanism (breakup due to turbulent eddies) were considered in the model. Local bubble size distributions at the top and bottom of the column were obtained by solving this PBE. The results were compared with the experimental data for seven independent multiphase systems (water/air, isomax diesel/air, kerosene/air and four other liquid mixture/air) at two diverse gas velocities. The experimental adjustable constant in the coalescence efficiency function was determined by fitting the population balance to the experimental bubble size distributions. An empirical correlation was proposed for the coalescence efficiency by the dimensional analysis, which includes Reynolds and Weber numbers. © 2011 Canadian Society for Chemical Engineering [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]

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]

Background: One of the most important challenges about the Membrane Bio Reactors is membrane fouling. Fouling has been at the centre of a globe debate for more recent years. It leads to high operational and maintenance costs such as membrane damage and replacement of membrane. Membrane fouling is attributed to the physicochemical interactions between the bio fluid and membrane. In order to decrease the fouling in bioreactors there are common anti fouling strategies such as operation at low flux, Optimization of aeration flow-rate and Physical and chemical cleanings. However, often they are not effective., Methodology: This work deal with fouling crisis by a new and innovative method in order to reduce of fouling on membrane surface by injection of parallel air jet on membrane bio reactor. This is a new idea and fundamental study about the influence of wall jet on fouling of membrane surface. This study is included both experimental and numerical investigations. In order to polarize the stream path on the surface of the membrane, four symmetric nozzles were implemented at the bottom of the membrane surface upon the sparger. The changes in the fouling resistance were experimentally measured at five various jet velocities and all of them recorded by a computer system. In addition the effect of air jet velocity and shear stress on fouling resistances was also investigated by computational fluid dynamics at the similar conditions., Results: It was revealed that the permeate flux and resistance of fouling can be related to shear stress of air flow at the membrane surface. When the velocity of air jets increase, the permeate flux increase too. Also, results illustrate that jet injection can partially remove the cake which was formed on the surface of the membrane., Conclusions: Correlations were developed for estimating each resistance of the membrane surface via the shear stress. The resistances of the cake are removed by the jet velocity changes, from 20% in lower jet velocity up to 40% in higher jet velocity.

In this study, high permeability flat sheet polysulfone nanofiltration membranes were prepared for amoxicillin (AMX) recovery from pharmaceutical wastewater. Membrane fabrication includes two steps: raw ultrafiltration membrane synthesis by phase inversion method and nanaofiltration membrane synthesis by surface photopolymerization. Raw ultrafiltration membranes were synthesized using different molecular weights of polyethylene glycol (PEG) as pore former and different coagulation bath temperatures (CBTs). The synthesized ultrafiltration membranes were modified using UV-assisted polymerization technique and their performance in the separation of AMX at different pHs, were studied. The results showed that the more irradiation time, the smaller surface pore size. Moreover, the membranes made with higher molecular weight of PEG and coagulation bath temperatures were more susceptible for UV-modification at these conditions; fabricated membranes had higher flux as well as relatively high AMX separation. Moreover, pH enhancement increased AMX rejection by 85%. The effect of irradiation on membrane surface morphology was studied by SEM surface images and the morphological effects of pore former and coagulation bath temperatures on membrane structure were confirmed by SEM cross section images. A fairly comprehensive discussion about the effects of PEG, coagulation bath temperature and irradiation time on membrane structure and AMX recovery performance was represented in this study.

This review discusses the characterization, production and implications of soluble microbial products (SMPs) in biological wastewater treatment. The precise definition of SMPs is open to talk about, but is currently regarded as "the pool of organic compounds that are released into solution from substrate metabolism and biomass decay"'. Some of the SMPs have been identified as humic acids, polysaccharides, proteins, amino acids, antibiotics, extracellular enzymes and structural components of cells and products of energy metabolism. They adversely affect the kinetic activity, flocculating and settling properties of sludge. This review outlines some important findings with regard to biodegradability and treatability of SMPs and also the effect of process parameters on their production. As SMPs are produced during biological treatment process, their trace amounts normally remain in the effluent that defines the highest COD removal efficiency. Their presence in effluent represents a high potential risk of toxic by-product formation during chlorine disinfection. Studies have indicated that among all wastewater post-treatment processes, the adsorption by granular activated carbon combined with biologically induced degradation is the most effective method for removal of SMPs. However, it may be concludes that the knowledge regarding SMPs is still under progress and more work is required to fully understand their contribution to the treatment process.