ABSTRACT
Background: Heavy metals have destructive and irreversible effects on the human, plants and animals. Some industries in Yazd enter industrial wastewater to municipal wastewater collection system. This can lead to high levels of heavy metals in wastewater and in turn in the wastewater treatment plant effluent
Methods: This study was carried out during four months from December 22, 2009 to May 20, 2010. The experiment was performed on the inflow, outlet of anaerobic pond and first and second facultative ponds of wastewater treatment plant and then transferred to the laboratory and measured by atomic absorption spectroscopy
Results: The results of the experiments showed that the average cadmium concentrations in the inflow, anaerobic pond outlet, and first and second facultative pond outlet were 0.0066, 0.0087, 0.0076, and 0.0083micro g/l, respectively. The average amounts of chromium in the inflow, anaerobic pond outlet, and first and second facultative pond outlet were 0.0076, 0.0065, 0.0043, and 0.0056 micro g/l, respectively. Cadmium concentration in the effluent was higher than standard
Conclusion: The comparison of the obtained data with Iranian standards for wastewater treatment for reuse in irrigation shows that the cadmium concentration exceeded the standard and the chromium concentration was lower than the standard. Therefore, it is not suitable for reuse in the crop farms and aquatic life
ABSTRACT
Background: The presence of heavy metals in the environment especially in water supplies have caused many concerns because of their toxicity and non-degradability. Hexavalent Chromium [Cr] is one of the most toxic metals which is used in many industries, so it is essential to remove it from industrial wastewater. In this study, we made a comparison between different adsorption isotherms in the chromium [VI] removal process using carbon nano tubes from aqueous solutions
Methods: This experimental study used atomic absorption spectrophotometry. To determine the adsorption isotherms, a synthetic sample with defined concentration of Cr [VI] was prepared and different doses of adsorbent were added to it. The effect of initial Cr concentration, pH, adsorbent dose, and reaction time on removal of Cr was investigated. Temperature and mix rate were steady during a defined time. At the end, Cr [VI] concentration measured and adsorbents equality capacities were calculated via formulas and graphs. Data analysis were performed using descriptive statistics
Results: Adsorption capacities [q[e]] increased with increasing of initial Cr concentration, and reaction time decreased with increasing adsorbent dose and pH. Correlation coefficients for Langmuir, and Freundlich isotherms in oxidized Multi-Walled Carbon Nano Tubes [MWCNTs] were 0.93, 0.874, and 0.714 and in oxidized Single-Walled Carbon Nano Tubes [SWCNTs] were 0.904, 0.868, and 0.711 respectively
Conclusion: Chromium ions adsorption in carbon nano tubes is accordant to Langmuir isotherm model, and MWCNTs have more cc than SWCNTs. Carbon nano tubes are effective adsorbents in removal of Cr [VI] from aqueous solutions
ABSTRACT
Cholera is a bacterial infection that causes both local outbreaks and worldwide pandemics. There was a cholera epidemic in Iran in summer 2005, during which 1118 individuals were infected and 11 died. The present study was conducted to determine the impact of educational activities of Iranian Ministry of Health on the people's knowledge and attitude towards the disease. This cross sectional study was carried out on 240 subjects. Samples were selected by cluster sampling in Yazd, Iran. Data were collected by a prepared questionnaire and analyzed by student t- test and chi square, when appropriate. Mean scores of subject's awareness before and after outbreak were 4.5 and 10.5, respectively [p<0.05]. Only 33% of subjects knew cholera as a transmittable disease, however, following the intervention, the respected percentage reached up to 99.5%. Our study showed that few people were aware of cholera, however, their awareness improved significantly following the education. Therefore, effective continuous educations should be attempted, especially through mass media, in order to reduce the health and economic impacts of endemic diseases