Iranian Journal of

Background & Objectives: Entering LAS through the wastewater plant’s effluent to water resources causes taste and odor changes, aquatics death, oxygen transfer limitation, and disorders in water treatment processes. Therefore, the study objective was to determine optimum conditions for fenton oxidation process to remove linear alkyl benzene sulfonate from aqueous environments using taguchi method and its requirement evaluation for additional treatment of Biolac effluent. Materials &Methods: LAS removal using Fenton oxidation was evaluated in a 500 mL laboratory-scale batch reactor. In order to save the costs, to determine the optimum conditions of the Fenton oxidation, 25 runs were computed using Taghuchi method by Minitab 16 software. Sampling and required tests were performed based on standard methods examination for water and wastewater. For evaluation of Biolac process sufficiency in LAS removal, biolac efficiency in Urmia Wastewater Treatment Plant was studied in 2012. Results: Based on the LAS removal and chemicals required, Minitab software (Ver. 16) recommended the optimum conditions of Fenton oxidation at 900 mg/L H2O2, 170 mg/L Ferrous ion, pH of 4, and reaction time of 20 minutes. It was found that the Fenton oxidation for LAS removal had 86.5% efficiency under optimum condithions and it was second order reaction with the rate coefficient of 0.0152 L/mg.min. Biolac process does not need any additional treatment due to meeting LAS standard in municipal wastewater treatment. Thus, this process decreased annually mean LAS from 5.28 mg/L to 0.734 mg/L in municipal wastewater. Conclusion: Although the Fenton oxidation appears as a chemical process with high efficiency in the removal of LAS, the low efficiency of COD corresponding to the LAS indicated partial decomposition of linear alkyl benzene sulfonate by Fenton oxidation.

Background and Objective: Phenol and phenol derivatives in industrial wastewater are among the pollutants with priorities. The high cost and low efficiency of some routine treatment processes of industrial wastewater has limited their use. One of the new methods under consideration is, nowadays, adsorption using carbon nanotubes. This study was conducted in order to evaluate the application of alumina-coated multiwall carbon nanotubes in eliminating phenol from synthetic wastewater. Materials and Methods: This study was performed in laboratory at batch scale. Multi-wall carbon nanotubes were coated with Alumina. The concentration of phenol was determined by spectrophotometer through photometry. The effect of pH changes, dosage of adsorbent, contact time, the initial concentration of phenol, temperature, and the concentrations of different salts on the efficiency of absorption was evaluated. Then, the absorption results were described using the Langmuir and Freundlich isotherms and the synthetics of absorption. Results: It was found that absorption efficiency increased significantly by decreasing the initial concentration of phenol and pH and by increasing the carbon nanotube dosage, temperature, and contact time. On the other hand, the maximum elimination of phenol from the solution (98.86%) occurred at 4 mg/l phenol concentration, under acidic conditions (pH=3), at adsorbent dosage of 0.05 g/l, at temperature of 45°C, and contact time of 10 min. Evaluation of the regressions isotherms showed that the process follows the Langmuir model and second-degree synthetic absorption. Conclusion: The high efficacy (98%) of the adsorption process in this study showed that alumina-coated multiwall carbon nanotubes have a good capability in eliminating phenol and can be used as an appropriate and new method for eliminating phenol and its derivatives from wastewater.

Background and objective: Benzene is one of the main pollutants in air and one of the most extensive chemical compound used in both natural and industrial processes. Benzene exposure leads to the most dangerous adverse health effects, particularly blood cancer. The aim of this study was to evaluate the gas station workers’ exposure to benzene by measuring benzene in breathing air and urinary trans, trans-muconic acid. Materials and Methods: This cross-sectional study conducted in summer 2014 investigated 40 gas station workers and 40 occupationally non-exposed persons. Spot urine samples were obtained prior to and at the end of the work shift from each subject. The urinary levels of trans, trans-muconic acid was determined by liquid chromatography (HPLC) with diode array detector. At the end of the work shift, the benzene collected on sorbing cartridges was desorbed using carbon disulfide and was analyzed using gas chromatography and mass spectrometry detection. Results: The mean value for exposure to benzene in breathing zone of gas station workers was 5.90 ±1.93 ppm, which was significantly greater than the occupationally non exposed group (1.15±0.744 ppm). The mean urinary concentrations of trans, trans-muconic acid differed significantly between samples of gas station workers (64.75±19.47 µg/L) and occupationally non-exposed persons (47.10±13.67 µg/L). Conclusion: A good correlation (r = 0.581) between the mean values of benzene in breathing zone and the urinary concentration trans, trans-muconic acid was observed. Gas station workers were found to be probably the most exposed groups in this study. Inhalation is presumably the main route of exposure in gas station workers.

Background and Objective: One of the air pollutants is volatile organic compounds (VOCs). Benzene, as a part of petrol, is a VOC, known to be carcinogenic to human beings (Group 1) and it has widespread application in  various industries and professions. Hence, the aim of the present study was semi-quantitative and quantitative health risk assessment of petrol bank workers exposure to benzene via inhalation in the Tehran, Iran.

Material and method: For these purpose, this descriptive cross-sectional study was conducted in three stages. First stage consisted of measurement of benzene in two groups of participants: (1) petrol bank workers and (2) non-exposed people as control group. The second stage included the evaluation of worker^'s exposure to benzene and semi-quantitative risk assessment, and the third stage was estimating the lifetime cancer risk caused by exposure to benzene.

Results: Benzene mean concentration was near the threshold limit value (1600 µg/m³) and the mean benzene personal air level was 1527±246.4 µg/m³ in the petrol bank areas. With regard to semi-quantitative risk assessment method, benzene introduced as the most hazardous chemical with risk ratio of 4.5 has 5^th rank in risk levels (Extremely dangerous). Lifetime cancer risk estimation showed that in petrol bank workers the excess lifetime cancer risk was 27.5 times higher than unexposed group and the chance of cancer was one in a 1000 petrol bank workers.

Conclusion: This study indicates that petrol bank workers in Tehran have a potentially high cancer risk through inhalation exposure. Thus, preventative actions regarding to this hazardous and carcinogenic chemical must be started as soon as possible.