Removal of Selenium from Wastewater using ZVI and Hybrid ZVI/Iron Oxide Process
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Selenium (Se), often in form of selenocyanate (SeCN-), which present in some of refinery process wastewater known as stripped sour water. As Se discharge is increasingly regulated, the industry struggles to find a cost-effective technology for SeCN- treatment. Zero-valent iron (ZVI) technology, with some successes in remediating toxic-metal contaminated groundwater remediation, emerges as a potential solution for addressing SeCN- problem. In this study, bench scale tests were conducted to investigate the removal of SeCN- from wastewater with ZVI. The removal efficiency was evaluated by a series of tests under different conditions such as initial pH, various ions, ZVI particle size, dissolved oxygen (DO) and iron oxide. Results showed that SeCN- was effectively removed from wastewater with ZVI and Fe(II) filings when the water pH was controlled at approximately 6 with sufficient DO. The further evaluate of treating SeCN- using hybrid zero valet iron (hZVI) system has also been conducted in this study. The hZVI system process is a novel chemical treatment that has shown valuable potential for removing several heavy metals from wastewater. This study concluded that at bench scale, the removal efficiency of SeCN- in the wastewater is over 99% with 2-steps of hZVI reactors and a HRT of 12 hours. In essence, this study concluded that ZVI is a highly valuable potential cost-effective treatment for SeCN- removal from wastewater and the results from bench scale hZVI system can be effectively used to scale up the system to serve the industrial needs in the future.