Iranian Journal of

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Backgrounds and Objectives: Volatile organic compounds (VOCs) are one of the common groups of contaminants encountered in the industrial activities, emitted through air stream into the atmosphere. To prevent the human and environmental health from the adverse effects of VOCs, air streams containing VOCs need to be treated before discharging to environment. This study was aimed at investigating the catalytic ozonation process for removing xylene from a contaminated air stream.
Materials and Methods: In the present work, a bench scale experimental setup was constructed and used for catalytic ozonation of xylene. The performance of catalytic ozonation process was compared with that of single adsorption and ozonation in removal of several concentration of xylene under the similar experimental conditions.
Results: The results indicated that the efficiency of catalytic ozonation was higher than that of single adsorption and ozonation in removal of xylene. The emerging time and elimination capacity of xylene for inlet concentration of 300 ppm was 1.4 and 5.8 times of those in adsorption system. The activated carbon acted as catalyst in the presence of ozone and thus attaining the synergistic effect for xylene degradation.
Conclusion: catalytic ozonation process is an efficient technique the treatment of air streams containing high concentrations of xylene. The adsorption systems can also be simply retrofitted to catalytic ozonation process and thereby improving their performance for treating VOCs.

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Background and Objectives: city bus drivers, during driving, are always exposed to the whole body vibration. This can lead to central- neural, musculoskeletal, and blood circulation disorders and develop occupational diseases due to vibration. The objective of this descriptive- analytic study is to investigate Tehran bus drivers&apos exposure to the whole body vibration.
Materials and Methods: We measured parameters related to the whole body vibration, such as acceleration of the frequency weighted root sum of squares, the overall equivalent acceleration, vibration dose value, and crest factor were measured separately at three directions (X, Y, Z) in 80 buses in 5 different types, which were selected randomly. The results obtained were compared with ISO 2631: 1997 Standard, and finally permitted driving time was calculated for different buses.
Results: Acceleration of the frequency weighted root mean of squares at X, Y axes in all of the buses was below the district of health warning and at Z axis, it was in the district of health warning, while the overall equivalent acceleration in Icarus buses was above the district of health warning and in other buses it was in the district of health warning according to standard ISO 2631: 1997. Vibration dose value (VDV) was less than 8.5 and crest factor was less than 9 and in all of the buses, it was less than the suggested permitted limits of ISO 2631: 1997 standard. Moreover, permitted driving time was estimated less than 8 hours per day and Icarus buses had the most and Man buses had the least vibration acceleration, crest factor, and vibration dose value respectively.
Conclusion: According to the results obtained, there is the possibility of developing potential health risks in bus drivers therefore, it is recommended that the health and safe managers consider decrease of working hours and increase of rest time while purchasing new buses.

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MicrosoftInternetExplorer4 Background and Objectives: Formaldehyde is a toxic substance and harmful to human beings and the environmental health. Therefore, the effluents containing formaldehyde have to be efficiently treated before discharging into the environment. This study was aimed at investigating the efficiency of Electro-Fenton (EF) Process in pre-treating industrial wastewater containing high concentrations of formaldehyde.
Materials and Methods: The effect of the important operational variables including pH, current density, H₂O₂ dosage, and reaction time were evaluated on the degradation of 7500 mg/L formaldehyde using batch tests. The EFP batch reactor was consisted of a cylindrical glass column with 5.20 cm in internal diameter and 34.50 cm in height. Working volume of the reactor was 500 mL.
Results: The maximum formaldehyde removal was obtained at alkaline pH of 10, H₂O₂ concentration of 10 mM/min, current intensity 8.5 mA/cm2, and the reaction time of 6 minute. Furthermore, aerating the EFP cell could enhance the formaldehyde removal. Complete removal of formaldehyde was obtained under the abovementioned operational conditions.
Conclusion: This study demonstrated that the EFP is capable of reducing high concentration of formaldehyde (7500 mg/l) to the level suitable for biological post-treatment.