Pilot-scale demonstration of the hybrid zero-valent iron process for treating flue-gas-desulfurization wastewater: Part II

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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 Hg2+ 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 m3 FGD wastewater treated at a cost of about US$0.6/m3. 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.

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