مهندسی عمران شریف (Nov 2017)
REMOVAL OF ZINC AND NICKEL FROM WASTEWATER TREATMENT SLUDGE BY COMBINED MAGNETIC SEPARATION AND LEACHING WITH ENHANCED ELECTROKINETIC PROCESS
Abstract
Heavy metals are among the most serious environmental pollutants. Contamination of industrial waste water treatment sludge with heavy metals represents a potential threat to human and animal health. Electrokinetic remediation is one way of removing pollutants such as heavy metals from the contaminated soils. This technique is also highly cost-effective and practical for remediation of industrial sludge. In electrokinetic remediation a low-intensity electrical current is made to flow through electrodes (cathode and anode) embedded in the contaminated soil. Small ions and charged particles migrate between the electrodes encased with water. Due to electrical potential differences, pollutants, such as heavy metals influenced by the flow of electric current, move into the electrolytic solution. The main objective of this study is to investigate the effect of magnetic separation and sulfuric acid leaching pretreatment as a way of boosting zinc and Nickel removal from industrial wastewater sludge through an electrokinetic process. This laboratory-scale study uses real sludge samples taken out from a wastewater treatment plant of industrial park. In this study, changes in pH, electrical current, electro-osmosis flow and energy consumption in different processes have been studied and the ability of each processes for the removal of zinc and nickel from sludge is determined. The results of pre test showed that enhanced electrokinetic process (the use of EDTA and citric acid as the electrolyte) compared with conventional electrokinetic (the use of water as the electrolyte) has a better performance in the removal of metals from the sludge. In this study, removal of zinc using enhanced electrokinetic process was 31\% more than that in conventional method. The results revealed that leaching-electrokinetic combined process increases the removal efficiency of zinc and nickel to 94\% and 82\%, respectively. Decreasing pH and removing unwanted elements by leaching were the major factors to improve the electrokinetic performance. The results also showed that the magnetic separation-electrokinetic combined process has no considerable effect on heavy metal removal from sludge.
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