Iranian Journal of

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Backgrounds and Objectives:Arsenic is one of the most toxic and dangerous elements in drinking  water that with increase in its application in agriculture, development of applications in agriculture, livestock, medicine, industry and other cases its entry to water resources and environment is much easier.Arsenic is a poisonous, cumulative substance and inhibitor of SH group enzymes and various studies revealed a significant correlation between high concentrations of arsenic in drinking water and liver cancer, nasal cavity cancer, lungs, skin, bladder and kidney cancer in men and women and prostate and liver in men. The aim of this was survey of arsenic removed from water using dissolved air floatation mechanism.
Materials and Methods: At present study in first step for determination best conditions of arsenic removal by dissolved air floatation method, optimum amount of coagulants determined and then synthetic solution of arsenic (50, 100 and 200 µg/L) prepared using sodium arsenate. In third step arsenic removal efficiency under various variables such as arsenic concentration, flocculation and floatation time and saturation pressure were analyzed. Finally residual arsenic concentration was determined by the silver diethyl dithiocarbamate method.
Results:Effect of optimum condition on arsenic removal efficiency at various initial concentration 50, 100 and 200 µg/Lshowed that the best coagulant for removal of arsenic is polyaluminumchloride. Also maximum efficiency (99.4%) was obtained in initial concentration equal 200 µg/L.
Conclusion: It can be concluded that dissolved air floatation method with poly aluminum chloride as coagulant have high efficiency for arsenic removal even at high concentrations and therefore this method can be used for removal of arsenic from water as a suitable and safe option.

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MicrosoftInternetExplorer4 Background and Objectives:  Presence of humic acids in water resources is important because it is a precursor to disinfection by-products (DBPs) and affects many treatment processes. In this study, we investigated the performance of electrocoagulation process duad with hydrogen peroxide (creating Fenton process) in removal of humic acids (HA) from aqueous environment.
Materials and Methods: The experiments were performed using a 1 L bipolar batch reactor (covered with the aluminum foil) equipped with iron electrodes and connected to electric source having electrical potential 10 V in bipolar mode. First, reactor was filled up using aqueous solution containing 20 mg/L HA. Later, several working parameters, such as initial pH (3, 5, 7, and 8), electrical conductivity produced from adding 1, 1.5, 2 and 3 g/l KCl and reaction time were studied to achieve the highest humic acid removal capacity. To follow the progress of the treatment, hydrogen peroxide (50 mg/l) was added to reactor and then samples of 10 ml were taken at 5, 15, 30, 45, and 60 min and then filtered (0.45 μ) to eliminate sludge formed during electrolysis. Finally, humic acid and iron concentration was measured using TOC analyzer and atomic absorption method respectively.
Results: Results of this study showed that the most effective removal capacities of humic acid (97.19%) could be achieved when the pH was kept 5(KCl 3g/l and reaction time 60 min). The share of Fenton and electrocoagulation process was %7.9 and %92.1 respectively. In addition, our results indicated that the removal efficiency of humic acid with increase of pH and electrical conductivity parameters decreases and increases respectively.
Conclusion: It can be concluded that the Fenton process duad with electrocoagulation process has the potential to be utilized for cost-effective removal of humic acid from aqueous environments.

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Background and Objectives: Slaughterhouse wastewater contains various and high amounts of organic matter (e.g., proteins, blood, fat, and lard). In order to produce an effluent suitable for stream discharge, chemical coagulation and electrocoagulation techniques have been particularly explored at the laboratory pilot scale for organic compounds removal from slaughterhouse effluent. The purpose of this work was to investigate the feasibility of treating cattle-slaughterhouse wastewater by combined chemical coagulation and electrocoagulation process to achieve the required standards.
Materials and Methods: At present study, slaughterhouse wastewater after initial analysis was tested for survey of coagulation process using Poly aluminum chloride (PAC) at various doses (25-100 mg/L). Then we measured the concentrations of wastewater pollutants (BOD5, COD, TKN, TSS and fecal Coliforms). Later, we transferred the effluent to the electrocoagulation unit and we evaluated the removal efficiency of pollutants in the range 10 to 40 volts of electric potential during 60 min.
Results: It was found that the efficiency of chemical coagulation process using poly-aluminum chloride (PAC) as coagulant increases with increasing doses (from 25 to 100 mg/L) we achieved maximum removal efficiency during the chemical coagulation for parameters of BOD5, COD, TSS, and TKN at 100 mg/L of PAC equivalent to 44.78%, 58.52%, 59.9%, and 39.58% respectively. Moreover, the results showed that with increasing the electric potential and reaction time, the yield increases linearly so that maximum removal efficiency at a dose of 100 mg/L PAC, an electrical potential of 40 volts and a reaction time of 60 minutes for the parameters BOD₅, COD, TSS, and TKN was 99.18% 99.25%, 82.55%, and 93.97% respectively.
Conclusion: The experiments demonstrated the effectiveness of combined chemical coagulation and electrocoagulation processes for pollutants removal from the slaughterhouse wastewaters. Consequently, this combined process can produce effluent compliance with the effluent discharge standards.

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MicrosoftInternetExplorer4 Background and Objectives: Phenol is one of the most important organic chemicals presenting in water and other environments. It not only brings about hygienic problems but also results in forming 11 toxic priority pollutants in aqueous environments. Hence, the performance of electrocoagulation process using iron and aluminum sacrificial anodes was investigated for removal of phenol.
Materials and Methods: We used a glass tank in 1.56 L volume (effective volume 1 L) equipped with four iron and aluminum plate electrodes to do experiments (bipolar mode). The tank was filled with synthetic wastewater containing phenol in concentration of 5, 20, 40, and 70 mg/l and to follow the progress of the treatment, each sample was taken at 20 min intervals for up to 80 min. The percent of phenol removal was measured at pH 3, 5, 7, and 9 electrical potential range of 20, 40, and 60 volts and electrical conductivity of 1000, 1500, 2000, and 3000 µs/cm.
Results: It was found that the most effective removal capacities of phenol (95 and 98 %) could be achieved when the pH was kept 7 and 5 for iron and aluminum electrodes, reaction time  80 min, electrical conductivity 3000 µs/cm, initial concentration of phenol 5 mg/l, and electrical potential in the range of 20-60 V.
Conclusion: The method was found to be highly efficient and relatively fast compared with existing conventional techniques and also it can be concluded that the electrochemical process has the potential to be utilized for the cost-effective removal of phenol from water and wastewater.

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Background and Objectives: Tous gas power plant as an emission source of gas pollutants is located in the northwest of Mashhad City. This power plant is located in the neighborhood of various (linear, point and area) sources of pollution including Tous thermal power plant, Tous industrial town and motor vehicles hence, it is not possible to determine precisely and accurately the share of these gases emission contribution at this power plant using conventional instruments. Therefore, we used modeling in order to estimate the dispersion of the pollutants emitted from this power plant.
Materials and Methods: we used Screen 3 software using data of exhaust fume concentration, mass emission, chimney features of each unit, meteorology data, and fuel types consumed in order to model dispersion of NOx and SO2 emitted from Tous gas power plant having V94.2 turbine equipped with DLN torches.
Results: Maximum concentration of NOx and SO2 at the distance about 30 km from the power plant was 1.08 and 3.69 µg/L respectively. The results of dispersion modeling of pollutants indicated that in most cases emission of air pollutants towards southeast. Conclusion: The NOx and SO2 concentration measured revealed that the concentration of these pollutants is lower than the standards of Clean Air Act.

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