Sharif Digital Repository

A tanks-in-series model was applied for mathematical modeling of the unsteady state performance of 70 and 100 liters airlift bioreactor for the production of lactic acid by fermentation. A set of first-order differential equations for the material balances of micro-organism, substrate, product, and dissolved oxygen around hypothetically well mixed stages was solved simultaneously utilizing computer program in MATLAB. The kinetic model utilized considered the effect of two substrates (glucose and dissolved oxygen) on the growth rate. The effect of air velocity on the lactic acid production was investigated. Results of this model have been validated with experimental data  

Conventional wastewater treatment systems demand a high cost mechanical aeration. Using algal-bacterial systems helps to reach a cost-efficient treatment method by eliminating mechanical aeration, since algae produce the oxygen needed for treatment process. In this study, two groups of experiments were performed for domestic wastewater treatment processes. For the first group, semi-continuous microalgae-bacterial photo-bioreactors were cultivated. Chlorella Vulgaris and activated sludge (AS) were used as microalgae and bacterial inoculums, respectively. The effect of different algae and AS ratios on the chemical oxygen demand (COD), N-NH4 + and P-PO4 3− removal was studied. The removal... 

In this study, a submerged membrane was installed in a bioreactor to treat N-riched wastewater and obtain high biomass productivity. Chlorella vulgaris was cultivated under mixotrophic, heterotrophic, and photoautotrophic conditions in different kinds of nitrogen sources (nitrate and ammonium) to compare the microalgae growth and nutrient removal in a membrane bioreactor. Further, the respirometric and photosynthetic activities of microalgae were investigated to evaluate the viability of microalgae in different conditions. The highest biomass productivity was obtained under mixotrophic cultivation in ammonium source (0.230 ± 0.009 gr/L d). Moreover, with this type of cultivation and nitrogen... 

To figure out the relationship between nutrient deprivation and cell growth, simulation can be effective. In the present work, the growth of Chinese Hamster Ovary (CHO) cells was simulated based on stoichiometric and kinetics calculations. The simulation results were compared to the experimental data from a packed-bed bioreactor and a good agreement was observed. The kinetic parameters (K Glc, K Amn, K Lact and μ Max) were optimized by a genetic algorithm method using stoichiometric parameters (Y X/Glc, Y X/Amm, and Y Lac/Glc). The stoichiometric and kinetic parameters were used in the simulation to study the growth of CHO cells. The concentrations of the toxic by-products, ammonium and... 

This work employs two membrane bioreactors (with and without carrier) to evaluate the influence of carrier and hydraulic retention time (HRT) on the sludge specifications when removing organic volatile compounds (e.g. styrene and ethylbenzene) from petrochemical wastewater. This study is conducted during three various HRTs. The results indicate that the optimum HRT (e.g. 15 h.) was achieved in the reactor with carrier during biological removal and membrane fouling minimization. During the optimum HRT, the biological removal efficiency for styrene, ethylbenzene, and COD is 99.8 ± 0.1%, 99.8 ± 0.1%, and 99 ± 0.8%, respectively, and the concentration of styrene and ethylbenzene in the exit air... 

In this paper, the fuzzy system has been used for fault detection and diagnosis of a yeast fermentation bioreactor based on measurements corrupted by noise. In one case, parameters of membership functions are selected in a conventional manner. In another case, using certainty factors between normal and faulty conditions the optimal values of these parameters have been obtained through the genetic algorithm. These two cases are compared based on their performances in fault diagnosis of a yeast fermentation bioreactor for three different conditions. The simulation results indicate that the fuzzy-genetic system is superior in multiple fault detection for the conditions where the minimum and... 

This work employs two membrane bioreactors (with and without carrier) to evaluate the influence of carrier and hydraulic retention time (HRT) on the sludge specifications when removing organic volatile compounds (e.g. styrene and ethylbenzene) from petrochemical wastewater. This study is conducted during three various HRTs. The results indicate that the optimum HRT (e.g. 15 h.) was achieved in the reactor with carrier during biological removal and membrane fouling minimization. During the optimum HRT, the biological removal efficiency for styrene, ethylbenzene, and COD is 99.8 ± 0.1%, 99.8 ± 0.1%, and 99 ± 0.8%, respectively, and the concentration of styrene and ethylbenzene in the exit air... 

The polycarbonate (PC)/thermoplastic polyurethane (TPU) blend membranes were prepared by phase inversion process applied to membrane bioreactor (MBR) to investigate the fouling characteristics. The impact of TPU and poly (vinylpyrrolidone) PVP concentration in polymer dopes on membrane structure, morphology, and performance were studied. The flat sheet fabricated membranes were characterized by scanning electron microscope (SEM), water contact angle (WCA), membrane surface roughness measurements and mechanical strength. The membrane performance was investigated at subcritical operating conditions. Pure water and critical flux through the fabricated membranes were measured for better... 

In this study, effects of solid concentration, temperature, and initial Fe2+ concentration on bioleaching of sulfide mineral (chalcopyrite) obtained from Sarcheshmeh Copper Mine in the region of Kerman located in the south of Iran were investigated. A mesophilic iron oxidizing bacterium, Acidithiobacillus ferrooxidans has been isolated from a typical chalcopyrite copper concentrate of the mentioned mine. Bioleaching experiments were carried out in two batch air-lift bioreactors with recycling stream. One reactor contained 2 liters of medium and 10% (v/v) inoculum while in the other reactor, control bioleaching tests were carried out with sterilized concentrate without inoculum by the... 

Due to the importance of environmental protection and the need to use new energy and alternative to conventional fuels, renewable energy has received much attention. Due to this necessity, a discontinuous bioreactor producing methane gas from animal waste has been modeled and simulated in this research. Monod kinetics was used to express the relationship between the growth rate of microorganisms and substrate concentration. The fourth-order Rong Kuta numerical method solved the substrate consumption and production of microorganisms and methane gas. The effect of the initial concentration of microorganisms on methane production has also been investigated. The initial concentrations of... 

Since the advent of conventional activated sludge biological treatment plants, their low efficiency in nitrogen and phosphorus removal has become a significant concern. Therefore, in this study, the performance of microalgal-activated sludge membrane bioreactor (MAS-MBR) as a self-biological treatment or as a post-treatment for conventional biological treatments was investigated. A continuous MAS-MBR with two ratios of algae/sludge (only microalgae and 5:1) was used to treat raw and treated wastewater. The optimum case was achieved with the cultivation of mixed algae/sludge in raw wastewater (R2 case). In this case, the ammonium and phosphorus removal efficiencies were 94.36 ± 3.5 and 88.37... 

A mesophilic iron oxidizing bacterium, Acidithiobacillus ferrooxidans, has been isolated (33 °C) from a typical chalcopyrite copper concentrate of the Sarcheshmeh copper mine in the region of Kerman located in the south of Iran. In addition, a thermophilic iron oxidizing bacterium, Sulfobacillus, has been isolated (60 °C) from the Kooshk lead and zinc mine near the city of Yazd in central Iran. Effects of some variable parameters such as solids concentration, temperature and pH on the bioleaching of chalcopyrite obtained from Sarcheshmeh copper mine were investigated. Bioleaching experiments were carried out in two batch airlift bioreactors with a recycling stream. The results indicate that... 

Bioreactor system has been used in bone tissue engineering in order to simulate dynamic nature of bone tissue environments. Perfusion bioreactors have been reported as the most efficient types of shear-loading bioreactor. Also, combination of forces, such as rotation plus perfusion, has been reported to enhance cell growth and osteogenic differentiation. Mathematical modeling using sophisticated infrastructure processes could be helpful and streamline the development of functional grafts by estimating and defining an effective range of bioreactor settings for better augmentation of tissue engineering. This study is aimed to conduct computational modeling for newly designed bioreactors in... 

The biological oxidation of ferrous ion by iron-oxidizing bacteria is potentially a useful industrial process for removal of H2S from industrial gases, desulphurization of coal, removal of sulfur dioxide from flue gas, treatment of acid mine drainage and regeneration of an oxidant agent in hydrometallurgical leaching operations. The main purpose of this study was to find optimum values of the process parameters on the ferrous biooxidation rate by immobilization of a native Sulfobacillus species on the surface of low density polyethylene (LDPE) particles in a packed-bed bioreactor using Taguchi method. Five control factors, including temperature, initial pH of feed solution, dilution rate,... 

The oxidation of ferrous iron in solution using Acidithiobacillus ferrooxidans has industrial applications in the regeneration of ferric iron as an oxidant agent for the removal of hydrogen sulfide from waste gases, desulphurization of coal, leaching of non-ferrous metallic sulfides and treatment of acid mine drainage. The aim of this attempt was to increase the biooxidation rate of ferrous sulfate by using immobilized cells. Rate of ferrous iron oxidation was determined in a packed-bed reactor configuration with low density polyethylene (LDPE) particles as support material in order to find the most practical system for scale-up. The present work studies the influence of basic parameters on... 

We develop a method for predicting the moisture content of the fermenting solids in an intermittently mixed packed-bed bioreactor on the basis of measurements of the inlet and outlet gas stream temperatures and the assumption that both the gas streams are saturated with water vapor. This method can be used to estimate when an intermittently mixed packed bed should be mixed and how much water should be added during the mixing event. The predictions were experimentally verified for the growth of Aspergillus niger on wheat bran in a thin packed bed. We show that the application of a controller based on our estimation method would have led to adequate moisture control, with significant errors in... 

Development of orbital shaking technology for enhanced mixing with lower mechanical demand has been receiving significant attention since the advent of advanced mixing schemes. Amongst shaken bioreactors, microtiter plates play significant role both for research and industrial purposes due to their capability of handling tiny amount of liquid in parallel experimentations. Detailed understanding of complicated Flow hydrodynamics thus seems to be considered a continual effort, as it is responsible for efficient gas-liquid mass transfer. Computational fluid dynamics (CFD) technique is shown to be a suitable numerical method in particular for discovering concealed flow facts, which can reliably...