Mohammad Reza Afshoon; Nasser Mehrdadi
Abstract
Introduction: In copper industries, mining has great importance from the environmental point of view, as many by-products are generated during this process. Most of the mining tailings are sulfide minerals that are oxidized after they are extracted and exposed to oxygen and water, which consequently ...
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Introduction: In copper industries, mining has great importance from the environmental point of view, as many by-products are generated during this process. Most of the mining tailings are sulfide minerals that are oxidized after they are extracted and exposed to oxygen and water, which consequently leads to the production of acid mine drainage (AMD). Water management strategies are conducted to control AMD. Generally, one of the most important methods to refine AMD and release it into the environment is treatment technology. AMD treatment methods are classified as active and passive systems. In the present study, the need for the treatment methods was investigated and then the optimum system was specified.Material and methods: Sungun copper mine is located in northwestern Iran, 130 km north of Tabriz and 30 km north of Varzeqan. The production rate of tailings in this mine is roughly 11.2 million tons per year, which has over 3 km2 area in Pakhir Valley. Samples of acidic drainage from Pakhir Chay River were collected 7 times and transferred to the laboratory of Omran Zist Azma Company. Bottles of polypropylene (200 ml) were used to gather samples for analyzing acidity, sulfate, and TDS, and HDPE bottles (250 ml) were used to gather samples for analyzing heavy metals (copper, iron, and manganese) parameters. Moreover, concentrated nitric acid was used for stabilizing the samples. The flow rate of the river was measured by Mouline (flow meter and flow cross-section method), which was on average 32 liters per second.Results and discussion: Analyzing the results of 7 sampling periods, it was found that the average value of pH, sulfate, copper, iron, and manganese parameters were 3.94, 2601.4, 276.78, 0.193, and 46.04 mg /l, respectively. According to the standard limits of the Environmental Protection Organization for discharging wastewater into surface water, all parameters except iron had exceeded the permissible limits, so a treatment system will be required before releasing AMD into the environment.Conclusion: Based on the quantitative and qualitative characteristics of the acid mine drainage in the present study and various acidic effluent treatment methods, it can be concluded that the active treatment method is a promising option to eliminate contaminants from the acidic effluent. Moreover, among the active purification methods, the DAOS method will have better efficiency so that it leads to higher efficiency of system’s operation, and the best quality output will be discharged into the environment.
Farshad Golbabaei Kootenaei; Nasser Mehrdadi; Mahdi Asadi-Ghalhari; Gholamreza Nabi Bidhendi; Hassan Amini Rad
Volume 15, Issue 1 , April 2017, , Pages 103-114
Abstract
Introduction: Sludge treatment in wastewater treatment plants is one of the most difficult challenges for professionals and officials (Heidari et al., 2014). The most important indicator of the presence of pathogens in the sludge and wastewater is the presence of coliforms (Tchobanoglous et al., 2003; ...
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Introduction: Sludge treatment in wastewater treatment plants is one of the most difficult challenges for professionals and officials (Heidari et al., 2014). The most important indicator of the presence of pathogens in the sludge and wastewater is the presence of coliforms (Tchobanoglous et al., 2003; Metcalf & Eddy, 2003). Ultrasound waves at frequencies of 20 to 200 kHz with high levels of energy is one of the new methods for disinfection of water and wastewater treatment plants (Foladori et al., 2010; Show et al., 2007; Pilli et al., 2011). The purpose of this study is to determine the effect of ultrasonic waves with a low wavelength to improve removal rate of total coliform and Escherichia coli in sludge and determine the optimum operating parameters of the ultrasonic method.Materials and methods: This study is a cross-sectional study that was conducted in a laboratory-scale batch. Accordingly, during two seasons, 12 samples were taken at an interval of 15 days. In this research, variables include ultrasound density (0.375, 0.75, 1, 1.3 and 2.5) in watts on ml and time (1, 5, 10, 15 and 30) in minutes. In this research the influence of these variables on the total coliform and E coli of sludge is measured. The ultrasonic device used in this study was a probe with a maximum output power of 750 watts and frequency of 20 kHz. All bacteriological tests were conducted using the MPN method in a few steps of possibility, confirmation and completion and they were performed using 15 tube methods with units of MPN per 100 ml. All the experiments have done in the Nano, Water and Wastewater laboratory of the Department of the Environment at the University of Tehran. All the experiments were performed on the basis of standard methods for water and wastewater experiments with No. 9221 (APHA, 2005).Results and discussion: With ultrasonic waves and through the destruction of the cell walls of pathogens, viruses and microbes and the disintegration of pathogens result in the disinfection of sludge. The high temperatures caused by cavitation can also be locally led for the elimination of pathogens. It seems that the hydrodynamic force and local high temperature zones caused by the cavitation phenomenon are the most important mechanisms influencing sludge disinfection process through applying ultrasonic waves. The results of this study showed that removal of total coliform and E. coli increased with an increase in the time and ultrasound density. The experiments determined that the optimum operating parameters are a sonification time of 30 minutes, ultrasound density of 2.5 W/ml in a frequency of 20 kHz. The removal rate of total coliform and Escherichia coli under these circumstances was more than 99 percent which is equal to the removal of 2 logs.Conclusion: Based on the results of this research, ultrasound waves can remove coliform and disinfect the sludge and can increase the treatment rate.
