Iranian Journal of

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MicrosoftInternetExplorer4 Background and Objectives: leachate from municipal solid waste landfill is a strong sewage having hazardous toxic substances. It should be treated by choosing a simple, economical, and eco-friendly method. The aim of this study is reduction of COD from the Qom City landfill leachate using electrocoagulation process.  
Materials and Methods: The experimental study was carried out at bench scale using a batch reactor during 2010.  We used a Plexiglas reactor having 0.7 liter capacity, containing nine plate aluminum electrodes connected to a DC power supply (10-60V, 1-5A). Samples were collected in the middle of cell at regular (every 10 minutes) time intervals. The concentration of COD was determined using a COD analyzer. The effects of different parameters including current density (52.08, 69.44 mA/cm²), electrolyte time (10, 20,30,40,50 and 60 min), and voltage range (10, 20, 30, 40, 50 and 60 volt) were investigated.
Results: For a voltage of 60 V and electrolysis time 60 min, the COD removal efficiency was increased from 48.7% for 52.08 mA/cm² to 77.4% for 69.44 mA/cm². The highest TSS removal efficiency was obtained at the largest current input when the voltage and electrolysis time were kept at 60V and 60 min respectively.
Conclusion: The results showed that the highest COD removal efficiency (77.4%) was obtained when the current density was 69.44 Ma/cm² and the voltage and electrolysis time were kept at 60V and 60 min respectively. Power consumption for this removal level was measured to be 431.26 kWh per kg COD removal. The results obtained revealed that the electrocoagulation technology is an effective treatment process for landfill leachate.

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Background and Objective: Important information can be obtained about the sources of pollutants in the atmosphere by studying the concentration of heavy metals in atmospheric precipitation.. Therefore, in this study concentrations of Pb, Zn and Cu were measured in samples of urban watershed of Bojnourd in autumn and spring seasons to help urban managers to control pollution in Bojnourd area.
Materials and Methods: This study was a descriptive and cross-sectional research. 24 samples of rain water were collected to measure heavy metals. The amount of heavy metals in the samples was measured using atomic absorption.
Results: Results showed that the pH was alkali in the Bojnourd urban watershed. Concentrations of Pb, Zn and Cu in rainwater in both autumn and spring were compared to international standards of WHO and EPA. The difference was significant (P <0.05) and was less than the standards values. Also, the results of the Pearson correlation test showed that the highest positive correlation was between zinc (r = 0.733) and copper (r = 0.190) in the samples of autumn and spring. This correlation was approved using hierarchical cluster analysis method.
Conclusion: The low levels of pH and low concentrations of heavy metals in comparison with global standards indicated low rainwater pollution to heavy metals. Thus, there is no a health threat to the people of the city. The concentration of heavy metals in the metropolitan area of urban watersheds had been higher than other basin levels and the most dominant contaminant was lead in the residential and commercial areas with the highest urban traffic. The pollution to heavy metals varied in different seasons and the value was higher in spring rainwater samples than the autumn ones.