RESUMEN
The hybrid zero-valent-iron (hZVI) process is a novel chemical treatment process that has shown promise for removing heavy metals and nutrients from industrial wastewaters. In this study, a pilot-scale demonstration was conducted to continuously treat 3.8-7.6 L/min (1-2 gpm) of the flue-gas-desulfurization (FGD) wastewater at a coal-fired power plant for 5 months. In this paper, a spike test was conducted to evaluate performance of the hZVI process for removing selected toxic metals at artificially elevated concentrations. The results showed that a multiple-stage hZVI process could decrease selenate-Se from 22 mg/L to ~10 µg/L and dissolved Hg(2+) from 1.15 mg/L to ~10 ng/L. In addition, the process simultaneously removed a broad spectrum of heavy metals such as As(III), As(V), Cr(VI), Cd(II), Pb(II) and Cu(II) from mg/L to near or sub-ppb (µg/L) level after a single-stage treatment. The process consumed about 0.3 kg ZVI per 1 m(3) FGD wastewater treated at a cost of about US$0.6/m(3). Solid waste production and energy consumption were reasonably low. The successful pilot study demonstrated that the hZVI technology can be a low-cost, high-performance treatment platform for solving some of the toughest heavy metal water problems.
Asunto(s)
Gases/química , Residuos Industriales/análisis , Hierro/química , Azufre/aislamiento & purificación , Aguas Residuales/química , Purificación del Agua/métodos , Electricidad , Metales Pesados/aislamiento & purificación , Microscopía Electrónica de Rastreo , Nitratos/aislamiento & purificación , Proyectos Piloto , Dióxido de Silicio/aislamiento & purificación , Solubilidad , Contaminantes Químicos del Agua/aislamiento & purificación , Contaminantes Químicos del Agua/toxicidad , Difracción de Rayos XRESUMEN
The hybrid zero-valent-iron (hZVI) process is a novel chemical treatment process that has shown great potential in previous laboratory and field bench-top scale tests for removing selenium, mercury and nutrients from various industrial wastewaters. In this study, a pilot-scale demonstration was conducted to continuously treat 3.8-7.6 L/min (1-2 gpm) of the flue-gas-desulfurization (FGD) wastewater at a coal-fired power plant for five months. Results show that the hZVI process could simultaneously reduce selenate-Se from 1 to 3 mg/L to below 10 µg/L and mercury from over 100 µg/L to below 10 ng/L in compliance with the new stringent effluent discharge limits planned by the U.S. EPA for Se and Hg. A three-stage hZVI system with a combined hydraulic retention time of 12 h is sufficient for Se treatment, while a single-stage system can meet Hg treatment requirement. The successful pilot study demonstrated that the hZVI process is scalable and could be a reliable, low-cost, high-performance treatment platform with many application potentials, particularly, for solving some of the toughest heavy metal water problems.