Abstract: Pendimethalin is a persistent herbicide. It is the third most widely used selective herbicide applied in soil that negatively affects humans and the environment. The current experiment assessed the ability of three bacterial species to degrade this herbicide. Pendimethalin was added to flasks in a 125 mg.L-1 concentration and 107 CFU.mL-1 of Bacillus subtilis, Pseudomonas fluorescens, and Escherichia coli were added separately to the mineral salts medium media (MSM) and stored on a rotary shaker. The bacterial cell number, wet biomass, and chemical oxygen demand (COD) were determined after seven days. The concentration of pendimethalin residue was then determined using high-performance liquid chromatography (HPLC). A completely randomized design (CRD) with three replicates was used to arrange the experimental units, except for HPLC with only one replicate. The experimental results showed that all three bacterial growths rose after seven days post-inoculation in the pendimethalin modified media. A comparison of the growth kinetics of bacteria in the herbicide modified media and the control showed that the bacteria grew faster in the presence of the herbicide. The reduction in the COD parameter occurred in all the tested bacteria, but the highest COD removal efficiency (85%) was observed with B. subtilis. The highest biological degradation of pendimethalin compared to the control occurred in the B. subtilis inoculated media (78%), which also produce the most cell density. Based on the HPLC results, all three bacterial species were capable of biodegrading pendimethalin herbicide, with B. subtilis as the most effective bacterium, followed by E. coli and P. fluorescens.
Abstract: Coagulants are used in drinking water treatment plants to increase the size of particles and to help make them bigger and more able to settle at the later stages of the process. Poly-aluminium Chloride was used in this study to evaluate its coagulation effectivity in different conditions. Three sets of experiments were done to determine the relationship between some raw water characteristics, including raw turbidity level, pH, and the temperature with optimum doses of PACL, in order to form a mathematical equation that could predict the removal effectivity. The experiments were performed under different seasonal circumstances. Four levels of turbidity were studied, 10, 50, 100, 150 NTU, with six different PACL doses from 5 to 35 mg/L. The results were used to build up a gene expression model (GEP). The GEP model gave very good results with a correlation coefficient equals to (0.91), and a root mean square error of 0.046.
Abstract: In the present study, the integration of the electrochemical process with membrane bioreactor was used as a new technology for leachate treatment. In the electro-membrane bioreactor (EMBR), aluminum electrodes were used as anodes and cathodes and EMBR was operated at a current density of 0.5 mA/cm2 and a solids retention time of 90 days to remove common contaminants such as ammonia-nitrogen (NH3-N), chemical oxygen demand (COD), phosphate (PO43--P) and ultraviolet absorbance at 254 nm (UV254). The maximum removal efficiencies of COD and NH3-N were above 98%. The average removal efficiency of PO43--P by EMBR system was 93%, which was significant compared to previous studies. The removal rate of humic substances based on UV254 was provided at approximately 96.95%. The trans-membrane pressure rate was acceptable for 80 days in EMBR, which could be related to sludge size improvement and filtration resistance through the occurrence of electrocoagulation, electrophoresis, and electroosmosis mechanisms. The mean removal efficiencies in EMBR were 90, 91.25, 96 and 87.5 % for chromium (Cr), cadmium (Cd), zinc (Zn), and iron (Fe), respectively. The slight change of mixed liquor-suspended solids (MLSS) in the leachate treatment reactor showed that the microorganisms in the new EMBR system had high adaptation. Based on the results, it can be decided that EMBR is a promising technology to improve leachate treatment performance due to the excellent removal efficiency of common contaminants, metal removal, and reducing fouling.
Abstract: Iran is located on Earth’s arid zone and drought crisis imperils the country as a result of declining water resources. Khuzestan Province is in critical condition due to water shortage, and many of its groves have been destroyed so far. Due to the constant presence of dust, Khuzestan Province has plenty of respiratory and pulmonary patients. In the current situation, this dust causes acute problems for the patients diagnosed with COVID-19. Considering the importance of water deficit in this province, the present research has been done by calculating SPI and SPEI in a thirty-year statistical period from 1984 to 2014, by selecting 12 stations, during the months in which rainfall is more likely. In this study, we utilized a geostatistical method to prepare zoning maps of SPI and SPEI, and then various spatial statistics techniques in ArcGIS software were used to identify and locate the exact areas that are the sources of drought with the help of drought hot spots and strong drought clusters. Anselin Local Moran's maps indicate that the high-high precipitation clusters are located in the northeastern regions of Khuzestan. Drought hot and cold spots which were identified by Getis-Ord G* spatial statistics based on both SPI and SPEI show that the hot spots are formed in the southern and southwestern regions; while the cold spots are formed in the northwestern regions. Furthermore, drought hot spots have been identified with a 99% confidence level in places in which the total ten-year precipitation is less than 270 millimeters.
Abstract: Pesticides have been widely used in many fields such as livestock farming, aquaculture and agriculture. Preparation and characterization of iridium coated titanium anode (Ti/IrO2) and ruthenium coated titanium anode (Ti/RuO2) for Dicofol (DZ) degradation was examined using electrochemical oxidation process (EO). Scanning electron microscope (SEM) and X-ray diffraction (XRD) was used to characterize the metal oxide coated anodes. Operating parameters in EO such as current density, electrolyte (NaCl) dose, pH and electrolysis time for the degradation of Dicofol is studied in detail. Response surface methodology (RSM) coupled with Box-Behnken response surface design (BBD) was used to optimize and model the Dicofol degradation process. The Dicofol degradation and electrical energy consumption were taken as responses. Numerical optimization was used to determine the optimal conditions for Ti/IrO2 anode. (Current density of 0.1A, electrolyte dose of 3.5mM, pH of 7 and electrolysis time of 8 min). Under these conditions, the 93% of Dicofol was degraded with electrical energy consumption value of 0.75KWh/m3.
Abstract: The present study deals with the possible pre-treatment of municipal solid wastes (MSW) in anaerobic conditions and their co-disposal with bottom ash. In this objective, the effect of the addition of bottom ash on organic matter degradation was checked using different analyses. The obtained results showed a great reduction of organic matter in the presence of bottom ash (53% of a solid fraction is degraded instead of 18% for the control after 26 days of degradation). Consequently, methane production was more important for the leachate from a bioreactor mixed with the bottom ash, which reached 70.10 L/Kg in comparison with 50L/Kg for leachate from the control. The characterization of leachates by molecular tools revealed that the microorganisms responsible for organic matter degradation in anaerobic conditions belong to the Methanosarscina genera, and the methanogenesis reaction was acetate-dependent methanogenesis. To better understand the role of bottom ash in the acceleration of methanogenesis, molecular tools were used to identify the microorganisms in the bottom ash leachate after a leaching test. The obtained results showed the absence of microorganisms in the bottom ash leachate. The quantification by atomic absorption spectrophotometry (AAS) of dissolved iron, nickel, and cobalt in the bottom ash leachate after the leaching test, showed that the amounts of these metals were 57.30, 0.035, and 0.006mM, respectively. Moreover, the quantification of iron, nickel, and cobalt in leachates from the bioreactor mixed with bottom ash and from the control showed that these amounts reached 94.78mM, 0.49mM, and 0.01mM after 26 days of degradation, and 99.40mM, 0.08mM, and 0.009mM, respectively, after 138 days of degradation. Consequently, it can be suggested that bottom ash must be co-landfilled with municipal solid wastes at 9% as a suitable strategy, which will provide a more rapid chemical and microbiological stabilization of the municipal solid waste in landfills.
Abstract: A large amount of fruit and vegetable waste is generated every day in big cities. The efficient disposal of such biodegradable waste can be considered a challenge. Leachate contains large amounts of pollutants and treating it is very complex, expensive, and requires a variety of hybrid processes. This study used the Analytic Hierarchy Process (AHP) to analyze suitable treatment methods for the leachate from fruit and leek fields. Quantitative and qualitative parameters or a combination of these parameters were used as defined in Expert Choice software. The criteria used for this purpose included chemical oxygen demand (COD), biochemical oxygen demand (BOD), COD/BOD, temperature, TOC, pH, total dissolved solids (TDS), total suspended solids (TSS), and time. These criteria, which are important for leachate classification, were identified and extracted by experts; their importance was ranked by AHP software. The research process was divided into two parts to ascertain a faster method: the significance of the parameter time and the insignificance of the parameter time. Biological treatment methods outperformed the other methods where the parameter time was insignificant. In the cases where the parameter time was significant, chemical methods and, in particular, two methods with ozone compounds (Ozone + GAC, Ozone + H2O2) outperformed the other methods.
Abstract: Cdo-TiO2 nanocomposites were synthesized by varying the molar ratio of CdO:TiO2 as 1:1, 1:2, and 2:1 using the sol-gel method. The pH value for all the CdO-TiO2 nanocomposites was controlled at two different values, pH-3 and pH-13. The nanocomposites were used for facilitating photolytic degradation of azo dye (Reactive Green-19). The surface morphology, crystallinity, and properties related to interactions with the light of the prepared catalyst were examined by scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and ultraviolet-visible (UV-Vis) spectrophotometer, respectively. The nanocomposites for all molar ratios synthesized at pH-3 showed rod-like structure and some irregular shapes, while those synthesized at pH-13 were spherical. From XRD patterns, composites at pH-3 and pH-13 were crystalline; however, those at pH-3 were more crystalline. The parameters, namely initial dye concentration, pH of dye solution, and catalyst concentration, affecting photocatalytic activities were examined and optimized at 75 ppm, pH-7.5, and 1g/l, respectively. The progress of the degradation process of Reactive Green-19 was observed by monitoring the change in the concentration of the dye after a certain time interval by measuring the absorbance by UV-Vis spectrophotometer. Catalyst A1:1 (The nanocomposites obtained at pH-3 with 1:1 mol% of CdO:TiO2) showed maximum degradation (94.53 %) at a catalyst concentration of 1 g/L.
Abstract: Petroleum sludge is typically caused by petroleum contaminants, effluents, and wastes from various stages of hydrocarbon separation. In this study, samples of oily sludge were collected from heavy fuel storage tanks in Sirjan Petrochemical Company in order to investigate the bioremediation of oily sludge by Eisenia fetida earthworms. The effects of oily sludge content, soil ratio, and sawdust weight percentage on total petroleum hydrocarbon (TPH) removal and reproduction of earthworms were evaluated. According to the design of the experiment (DOE), 17 samples with different combinations of petroleum sludge, soil, cow manure, and sawdust were selected to be tested. Also, to determine the effectiveness of the bioremediation process, some properties of samples including pH, total organic carbon (TOC), total Kjeldahl nitrogen (TKN), carbon to nitrogen ratio (C/N), and electrical conductivity (EC) were measured. The results showed that all properties, except for the electrical conductivity, decreased. Besides, in the presence of worms, the TPH could reduce by 66% after 90 days for samples containing up to 40 g oily sludge. Moreover, a statistical model was proposed using the response surface methodology (RSM) to predict the TPH removal and earthworm population as the targeted responses.
Abstract: In this study, a combined lab-scale purification system was set up for the treatment of Iranian oil company wastewater. The combined system is composed of three main sections: pre-filtration using activated carbon filter (ACF), electrocoagulation (EC) system, and filtration section (MF followed by RO). The performance of the treatment system was evaluated by measuring heavy metals, BOD, COD, TDS, TSS, and O&G. The results showed that the pre-filtration using ACF can lead to the removal of the BOD, COD, TDS, TSS, and O&G by 24.6%, 21.12%, 31.07%, 36.9% and 8.49, respectively and heavy metals were removed significantly. In the EC section, heavy metals were rejected by more than 98% using both Al and Fe electrode except for Cr ions, which was mostly removed with Fe electrodes. The removal BOD, COD, TDS, TSS, and O&G using Al and Fe electrode was obtained as 95.6%, 96%, 91%, 76.6% and 98.6% and 93.2%, 92.1%, 76%, 83% and 99%, respectively. EC followed by MF/RO filtration led to a remarkable purification performance so that the rejection rate of all pollutant were obtained over 99% after this section. Experimental results indicate that the optimum time for ACF and EC processes are 20 and 50 minutes.
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