Iranian Journal of Chemical Engineering (IJChE)

Abstract Sorghum bicolor L., a plant of Gramineae family is a perenial grass which is grown in many parts of tropical and warm temperates of the world. Sorghum seeds are rich in carbohydrates and can be used as fermentation medium providing it is produced through proper extraction and sacharification processes. In this study, the fermentation capacity of an aqueous or ethanolic extract from sorghum seed was investigated in Lab-scale bioreactors by using three selected Lactobacillus species including L. delbrueckii, L. acidophilus and a new isolated strain identified as a Lactobacillus sp.
Among the selected bacterial species, Lactobacillus delbrueckii was found to have unique characteristics as it could tolerate different physico-chemical conditions. Compared to other species, L. delbrueckii could remain metabolically active in high concentration of NaCl and lactic acid, which is particular to the fermentation of sorghum seed extract neutrilized by NaOH. L.delbrueckii could also tolerate high temperature and, additionally, was able to produce more lactic acid in high concentration of carbohydrate during fermentation process (Yield 85-90%). In conclusion, the results of this study demonstrated that hydrolysed sorghum seed extract has enough nutrients to support the efficient growth of lactic acid bacteria and production of lactic acid under favorable conditions (37°C, 100 g/L initial carbohydrate concentration).

Abstract Contrary to sandstone reservoirs, carbonate reservoirs have an oil-wetting nature. Water flooding of these fractured reservoirs with low permeability matrix blocks is not recommended unless a wettability alteration process is possible. Imbibition is an oil recovery mechanism for these types of reservoirs, if the rock matrix is water wet and there is enough water in fractures in contact with the matrix. Heavy matrix oil, high interfacial tension (IFT), oil-wet matrix sample, and limited contact area of matrix with water in fractures, requires additional effort to enhance the oil recovery by capillary imbibition. Surfactants can be injected into naturally fractured reservoirs to improve the capillary imbibition recovery performance. A well-known surfactant is Hexadecyl Trimethyl Ammonium Bromide (C 16TAB), which is an appropriate type of surfactant for these kinds of reservoirs. However, due to its high cost, it is rarely used in the real case
studies. In the present paper a simple and inexpensive method has been proposed for synthesizing this surfactant. Surfactant at different concentrations have been dissolved in high salinity brine, and the interfacial tension (IFT) between the aqueous solution and the oil has been measured by pendent drop method. In addition, the contact angle between the oil and the aqueous solution is measured by sessile drop method, and during the experiment, photos were taken every two seconds in order to analyse the IFT and the contact angle obtained. It has been found that reduction of IFT continues up to critical micelle concentration of the surfactant. Furthermore, a correlation has been obtained to predict the IFT between the oil and the high salinity aqueous solution containing different surfactant concentrations. Finally, the best surfactant concentration is obtained for reservoir case studies.

Abstract Biodegradation of a mixture of benzene, toluene, ethyl benzene, and o-xylene (BTEX) was studied in a two-bed biofilter. The packing material was a mixture of sugarcane bagasse and granulated activated carbon. Aspergillus Brasiliensis and Aspergillus Niger fungi were inoculated in the biofilter, separately. The effects of BTEX concentration, Empty Bed Residence Time (EBRT) and temperature on the biofilter efficiency have been studied. The results indicate that in the biofilter with Aspergillus Brasiliensis fungus, the removal efficiency approaches to 100% for the inlet load of 71.5 g.m -3 h -1 and EBRT of 2.7 min while total removal efficiency in the biofilter with Aspergillus Niger fungus is obtained for the inlet load of 140.3 g.m-3 h -1 and EBRT of 1.3 min. The maximum elimination capacity for this biofilter at inlet load of 223.08 g.m-3 h -1 and EBRT of 0.9 min is 188.95 g.m^-3 h ^-1 .

Abstract

Abstract In recent decades, large amounts of hydrocarbon derivations have contaminated the environment due to industrial developments and neglecting the environmental issues. In this study, the ability of biological removal of hydrocarbon pollution from contaminated soil around Sarkhun gas refinery was investigated. This study was done for seven samples with three different nutrient ratios and by moisture controlling and continuous aeration. During experiments, concentration of Total Petroleum Hydrocarbon (TPH) was measured. Results showed that with a nutrient ratio of 100:5:1 for C:N:P during an 18-day remediation period, the mean contaminant removal was about 50%. By using these results a practical plan was suggested for running in real scale situations. Developing a model was done by considering the Monod model as microbial growth model. Results showed good accordance to empirical data.

Abstract Soil bioremediation, especially in the rhizosphere area, is the result of interaction between plant roots and microorganisms. It can be considered as one of the remarkable ways to eliminate pollutants. Various factors control the process with special relationships in the rhizosphere environment; changing each of them can impress on the system destination. With mathematical modeling, behavior of the process can be predicted and controlled, and improved by appropriate changes in the model. In this study, the effects of different parameters of a simple mathematical model, represented to predict microbial growth and necessary substrate changes in the rhizosphere have been studied using numerical finite difference method. Influences of the parameters on biomass and substrate concentrations were evaluated at different times. A number of variables directly, some negatively, and others neutrally impacted on the biomass and substrate concentrations. Investigating variables differently affecting on a model is important since perfectly tuning them can optimize the system performance, and achieve higher efficiency.

Abstract Polyurea microcapsules containing an active agent, i.e. ethion as pesticide, have been prepared by interfacial polymerization between 2, 4-toluene diisocyanate (TDI) and diethylenetriamine (DETA) in an oil-in-water (O/W) emulsion system. The effects of the nature of the emulsifier, the monomer weight ratio, and a novel promoter, i.e. potassium phthalimide-N-oxyl (PPINO), on the morphology, microstructure, and thermal stability of the microcapsules have been investigated. PPINO was used as a water-soluble promoter capable of dimerizing and trimerizing the isocyanate reactant
in the interfacial polymerization. The transmission electron microscopy (TEM) micrographs showed that the addition of the promoter had no significant effect on the microcapsule shell thickness. Increasing the amount of PPINO caused the degree of crystallinity of the polymer shell to decrease considerably. In addition, increasing the amount of promoter up to 2 wt% caused the thermal stability of the microcapsules to decrease, while using promoter beyond this level resulted in higher thermal stability.

Abstract Soil contamination with TNT is a serious environmental hazard due to the toxic and mutagenic effects of TNT. Bioremediation is an environmentally safe method in the treatment of explosive-contaminated sites. In the present research, after selection of superior bacteria in the aqueous phase, bioremediation of TNT contaminated clay soil
at 1000mg/kg was performed in slurry phase, which resulted in a maximum TNT removal of 89% after 15 days. Afterwards, the effects of operational and environmental factors were examined via the two-level fractional factorial design method ( 7 3 IV2 − ) for seven factors, i.e., glucose (2, 8g/l), yeast extract (0, 0.2g/l), (NH 4)2SO 4 (0.1, 0.5g/l),
Tween80 (1, 5g/l) and slurry concentrations (20, 40%w/v) as well as inoculum size (5, 10%v/v) and temperature (20, 35˚C). Among these factors, significant factors were found to be slurry, surfactant and glucose concentrations as well as inoculum size. In addition, considerable interactions were observed between glucose and the other significant factors.

Abstract Contamination of soils with nitroaromatic hydrocarbons, due to their toxic effects, is one of the environmental issues. Therefore, the purpose of this study is to examine para-nitrophenol (PNP) biodegradation in a microcosm consisting of kaolan clayey soil by A. faecalis, the superior bacterium among the four examined bacterial species. Preliminary experiments were performed in slurry phase to investigate biodegradation of PNP by A. faecalis in shaking flasks at initial concentrations of 25 and 50mgkg-1  which resulted in 72 and 57% PNP removals after 20 days, respectively. To identify the effective factors on PNP biodegradation, experiments were carried out in shake flasks at various levels of eight factors, i.e. PNP, glucose and yeast concentrations, temperature, soil-water ratio, initial pH, inoculum size as well as PNP concentration in pre-exposure based on Plackett-Burman design method. Results showed 20.9 up to 75.5% PNP removal in soil slurry after 12 days within the design space. Analysis of variance revealed that temperature, inoculum size, yeast extract concentration, pH and soil-water ratio are the most effective factors on PNP biodegradation, respectively.

Abstract Plants and/or plant food wastes have been given much less attention or even disregarded. In some instances, however, oxidative enzymes from residual plant tissues have been shown to effectively degrade recalcitrant pollutants. Soybean seed coat peroxidase (SBP) is an inexpensive oxidoreductive enzyme and could be potentially used to oxidize/polymerize various organic pollutants of the industrial and petrochemical wastes. The catalytic properties of SBP are retained under a wide range of pH and at elevated temperatures. In the present study, the biocatalytic properties of SBP were estimated. The enzyme exhibited the highest activity and stability at pH 6.0 and retained over 75% of the maximum activity for 12 hours. The activity of SBP was found to be 2.5 times higher at an elevated temperature of 65°C compared to the activity at room temperature. The activity is retained over 95% for 30 min at 75°C. The pH and temperature of the reaction mixture showed significant influence on SBP activity. SBP is fairly active in organic solvents and exhibited the optimal activity in the presence of 20% (v/v) acetone. Increasing the organic solvent content resulted in a reduction in SBP activity.

Abstract This research work is concerned with the bioconversion of a heavy hydrocarbon cut from a petroleum refinery using native anaerobic consortia. The heavy cut is taken from one of the end-cuts of the vacuum distillation column of Tehran refinery which is normally fed into Isomax unit (a catalytic cracking process) called Isofeed. The consortia for this study were prepared from the petroleum-contaminated sludge and soils from Abadan, Shiraz, Isfahan and Tehran petroleum refineries of Iran. Nine microbial samples were collected (A, B, C, and I) and examined. Microorganisms were cultivated in an anaerobic medium to which Isofeed from Tehran refinery was added under anaerobic conditions. After twice sub-culturing the samples, the oil was separated from the liquid and examined to identify its bioconversion extent. For this
purpose, a column chromatograph method was used to separate saturates, aromatics and resins content of the oil. The results demonstrate that consortia A and C were able to increase the saturated and aromatics fractions of the oil and reduce the resins content of the oil. The saturated fractions of the bio-treated oil were also analyzed by a GC-MS analytical instrument. The GC-MS results revealed that the amount of normal chain hydrocarbons are reduced and the branched and cyclic hydrocarbons are increased.

Abstract Phenolic acids constitute a major group of pollutants which are recalcitrant to common biological treatment. In this study synthetic wastewater containing a mixture of p-coumaric and p-hydroxybenzoic acids was evaluated for photo-Fenton pretreatment. The changes in biodegradability (ratio of biochemical oxygen demand to total organic carbon (TOC)) and mineralization (TOC removal) were monitored. While there was a significant biodegradability enhancement during the photo-Fenton process, there was little mineralization (less than 6%) taking place over the course of oxidation. Longer oxidation time did not further improve the pretreatment; rather it decreased the biodegradability of the solution through complete mineralization of the biodegradable intermediates. Resin fractionation of treated solutions indicated an increase in the hydrophilic fraction and a decrease in the hydrophobic fraction.
Indeed, there was a clear and direct correlation between the hydrophilic nature of the organics and the biodegradability of the solution, indicating that hydrophilic compounds are more biodegradable. The formation of aldehydes further supported the links between biodegradable and hydrophilic compounds
 
 

Abstract
Uncontrolled release of light non aqueous phase liquids (LNAPL) such as diesel, gasoline, fuel oils and lubricating oils from transporting vehicles, pipeline and underground storage tanks (UST) could lead to the migration of contaminants to the subsurface soil and ground water. There is a high interfacial tension (IFT) between LNAPL molecules and water molecules that makes water a non-efficient cleaning material for removing LNAPL from the soil. Nowadays, surfactants (surface active agents) can promote the enhanced removal of LNAPL from the subsurface through mobilization and solubilization. Encouraging results were achieved from laboratory and field results. The aim of this study is to improve the clean up efficiency of surfactant-flooding for two different surfactants; Triton X-100 and Sodium Dodecyl Sulfate which are known as mobilizing and solubilizing surfactants, respectively, by adding alkaline (increasing pH) and foam producing substances. It is shown here that adding alkaline improves the performance of Triton X-100 in removing LNAPL from the contaminated soil by about 8 percent, but spoils the remediating capability of Sodium Dodecyl Sulfate by about 3 percent. Also, adding a foaming agent helps the surfactant solution in removing the LNAPLs out of the soil by more than 5 percent.

Abstract This investigation was designed to evaluate the effects of bioaugmentation on maintaining the system stability under shock loading conditions, standardizing the effluent, and improving the sludge settlement. In this study, phenol was chosen as a model of mono-aromatic compounds which are found commonly in many industrial wastewaters, especially petroleum refineries and the petrochemical industry in Iran. Impacts of bioaugmentation with the best isolated microorganism on the system performance facing sudden toxic shock were investigated after acclimatizing the system with phenol, isolating the phenol degrading microorganisms, and selecting the best phenol degrading strain. Results indicated that this method was improved the efficiency of the system under shock loading from 30% to 94% and SVI from 333 ml/g to 80 ml/g. The effluent was standardized after bioaugmentation at a minimum HRTs of 10, 10, 12 and 24 h, respectively, and at influent COD of 800, 1000, 1500 and 2000 mg/l. The system efficiency and SVI were located in an average range of 99.4-99.9% and 50-71 ml/g, respectively, and the sludge growth was good, even under high organic loading rates after bioaugmentation. In conclusion, bioaugmentation could be used as an effective and efficient method to improve a CAS process facing sudden toxic pollutant shock loading.

Abstract From an engineering point of view, the effect of light intensity distribution on the stability of growth rate should be taken into account in designing effective photobioreactors and sustaining stable growth rates. In the experiments described here, in order to keep operational parameters at an almost constant level, a semi-continuous culture method was developed for cultivation of photosynthetic cells under defined light intensity distributions. In the semi-continuous culture, a portion of culture broth containing grown cells was repeatedly replaced with the fresh medium at a predetermined time interval to maintain the cell concentration and the volume of the broth constant at their initial values. Under illumination from one and both sides, photosynthetic cells were cultivated in a flat plate photobioreactor with various light path lengths. The results obtained showed that stability of the growth rate strongly depended on the distribution of light intensity and the ratio of light intensity in the illuminated to that in the dark zone inside a photobioreactor. These parameters should be taken into consideration for stable cultivation of photosynthetic cells.

Abstract  Immobilization of Lipase produced from Rhizomucor miehei on HDPE fine powder was investigated. As compared to an aqueous system, immobilization in a non-aquous organic medium such as n-hexane was not successful and caused enzyme denaturation. Prewetting the support with ethanol increased the immobilized protein and enzyme activity as much as 31% and 34%, respectively. The maximum immobilized activity was obtained at the isoelectric pH of 4-5. The enzyme was suspected to have competition and/or interaction with other protein entities on the surface. Immobilization of the enzyme onto the support seems to be via shear sensitive weak physical adsorption. Proper duration of mixing was found to be around 6 minutes. Longer periods of shaking led to enzyme desorption, thereby reducing the immobilized activity. Neither efficiency nor stability was improved using glutaraldehyde as a cross-linking agent despite the fact that in some occasions, protein loading of the support was improved. This suggests the possible effect of glutaraldehyde on enzyme denaturation in these conditions. At optimum conditions, immobilized enzyme activity was enhanced almost 6-folds increasing from 8 units (per 0.5 ml of the enzyme liquor) to about 45.8 units (when 0.5 ml was immobilized on one gram of support).

Abstract