Environmental Health Engineering and Management Journal

7-14

Authors: Amirreza Talaiekhozani *, Zeinab Eskandari, Mohammad Reza Talaei, Malihe Salari

Background: In this study, ferrate (VI) and ultraviolet (UV) radiation were employed to remove hydrogen sulfide from municipal wastewater resulting in a reduction in chemical oxygen demand (COD). Although ferrate (VI) and UV have been used individually for the removal of a few pollutants from urban and industrial wastewater, there exists no study to investigate the effectiveness of simultaneous utilization of both methods for the removal of hydrogen sulfide and reducing COD. Methods: This study aims to compare the application of UV, ferrate (VI) and UV/ferrate (VI) for the removal of hydrogen sulfide and COD from municipal wastewater in batch mode. Moreover, the effect of many parameters such as ferrate (VI) concentration, temperature, hydraulic retention time (HRT) and pH on ferrate (VI) oxidation power, were investigated. Results: The results of this study demonstrated that for pH less than 2, higher pollutant removal efficiency was obtained. COD removal efficiency could increase up to 68% by adding 1.68 mg/L of ferrate (VI), almost 100% of hydrogen sulfide was removed by the same concentration of ferrate (VI). Both hydrogen sulfide and COD removal efficiencies increased as temperature increased to 50°C; nevertheless, further increase in temperature had negative effect on the removal efficiency. The use of UV/ferrate (VI) increased the removal efficiency of both hydrogen sulfide and COD when compared with the use of UV and ferrate (VI) individually. UV method was not effective in the removal of hydrogen sulfide. Conclusion: The research findings shed new light on wastewater treatment systems employing UV/ ferrate (VI) to decrease both the hydrogen sulfide and COD of municipal wastewater. This new findings will assist in the inaccurate design and effective operation of such systems which can be employed to maintain or improve environmental quality.

21-27

Authors: Soheil Sobhanardakani *, Lobat Taghavi, Behzad Shahmoradi, Amin Jahangard

Background: Iran is located within the dry and semi dry regions, thus almost 90% of the required water is secured via the use of groundwater. Owing to the increasing pollution of water resources, this study was performed to evaluate water quality pollution indices for heavy metals (As, Zn, Pb and Cu) contamination monitoring in Toyserkan Plain during spring and summer in 2012. Methods: A total of 20 ground water wells were chosen randomly. The samples were filtered (0.45 μm) and kept cool in polyethylene bottles. Samples were taken for the analysis of metals, the former was acidified with HNO3 to pH lower than 2. Metal concentrations were determined using ICP-OES. Results: The results revealed that the mean values of contamination index (Cd), heavy metal pollution index (HPI) and heavy metal evaluation index (HEI) in samples for spring season were -2.81, 9.74 and 1.20, respectively and were -2.67, 9.51 and 1.32, respectively in samples for summer season and this indicates low contamination levels. Comparing the mean concentrations of the evaluated metals with WHO permissible limits demonstrated a significant difference (P < 0.05). Thus, the mean concentrations of the metals were significantly lower than the permissible limits. Conclusion: Although the heavy metal pollution of the ground water in Toyserkan Plain is not higher than permissible limits, the irregular and long-term utilization of agricultural inputs, use of wastewater and sewage sludge in agriculture, over utilization of organic fertilizers and establishment of pollutant industries can threaten the ground water, and cause irreversible damages in this area.

37-43

Authors: Seyyedali Mirshahghassemi, Behnoush Aminzadeh *, Ali Torabian, Kamelia Afshinnia

Background: Car wash wastewater contains several contaminants such as organic matter, oil, grease, detergents and phosphates, all of which are harmful for the environment. In this study, the application of electrocoagulation (EC) to treat car wash wastewater has been studied, and the operating parameters optimized. The electro-Fenton (EF) for further contaminant removal was also investigated. Methods: In EC process, the effect of pH, current density, and the reaction time of the removal efficiency of chemical oxygen demand (COD), phosphate, and turbidity were investigated using the response surface methodology (RSM). The electrochemical cell consisted of four iron electrodes that were connected to a power supply using a monopolar arrangement. In the EF process, the effect of pH, reaction time, and hydrogen peroxide concentration on COD removal efficiency were probed. Results: The optimum pH, current density, and the reaction time for the EC process were 7.3, 4.2 mA cm-2 and 20.3 minutes, respectively. Under these conditions, the COD, phosphate, and turbidity removal percentages were 80.8%, 94.9% and 85.5%, respectively, and the specific energy consumption was 1.5 kWh m-3. For the EF process, the optimum pH, reaction time, current and hydrogen peroxide dosage were 3, 10 minutes, 2 A and 500 mg L-1, respectively. The EF showed higher COD removal efficiency (85.6%) with a lower specific energy consumption (0.5 kWh m-3) and reaction time compared to the EC. Conclusion: This study shows that both EC and EF can effectively treat car wash wastewater with high removal efficiency within a short reaction time.

55-58

Authors: Mohammad Aali Dehchenari, Saeed Hosseinpoor, Rahim Aali *, Nilowfar Salighehdar, Mohsen Mehdipour

Background: This research studied the feasibility of a simple method for extracting gold from central processing units (CPUs) of computer circuit boards without solvent. Methods: Ceramic and composite CPUs of computer circuit boards were used. Gold was extracted using a hydrometallurgical method in six stages: grinding of CPUs, leaching in nitric acid, leaching in aqua regia, removing the excess nitric acid, extracting the gold, washing and purifying the gold deposits. Measurements of extracted precious metals were carried out by inductively coupled plasma (ICP). Results: The results indicated that mean concentrations of gold in the first and second stages of leaching were 0.138 and 31.16 mg/L, respectively. Following the washing stage, the concentration of gold in the final deposit was 25 mg/L. The purity rate of the final deposit was 83.9%, and the final gold recovery yielded 82.3%. Conclusion: The results of this study indicated there is a potential for extracting a high percentage of precious metals from e-wastes without solvent.