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

Abstract

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.

Testing Metallic Iron Filtration Systems for Decentralized Water Treatment at Pilot Scale

“…This impression is supported by articles which reported on quantitative removal of species (e.g., 1,2-dichloroethane, dichloromethane, methylene blue, triazoles) which were proven to be not reducible by Fe 0 [83][84][85]. The performance of Fe 0 materials for water treatment has been adapted in recent years via multiple different methodologies, for a wide range of applications, including: (i) decreasing the particle size to nano-scale in order to enhance the reactivity of the material as a function of mass [86]; (ii) embedding noble bimetallic particles into the Fe 0 structure in order to improve the galvanic properties of the material [87]; (iii) embedding Fe 0 into appropriate porous support materials [14,48]; and (iv) embedding Fe 0 with complimentary adsorbent materials [88][89][90]. In addition, other metallic elements (namely Al has typically been demonstrated as superior due to its cost-effectiveness, bio-compatibility and long-term reactivity under natural conditions [96,97].…”

“…No consideration of these key issues has led to controversial reports which render the assessment of progress in designing Fe [8,9,54,58,[88][89][90][124][125][126]. In particular, the usefulness of mixing Fe 0 and inert (anthracite, pumice, sand) or reactive but non-expansive (Fe3O4, MnO2, TiO2) materials is still controversially discussed [125,127,128].…”

“…In particular, the usefulness of mixing Fe 0 and inert (anthracite, pumice, sand) or reactive but non-expansive (Fe3O4, MnO2, TiO2) materials is still controversially discussed [125,127,128]. Furthermore, an empirical approach has been used to screen selected operational factors like grain sizes and grain size distributions [126], grain packing [129] or the mixture of Fe3O4 and external Fe II solutions [88][89][90]. This empirical approach is certainly costly but not necessarily effective [121][122][123].…”

“…The authors concluded that "the mixed reactive filters" are not applicable for treatment of the "tested groundwater with its indigenous microorganisms". This conclusion is erroneous for at least A second example showing how the results of Westerhoff and James [124] were not properly considered is presented by Huang et al [88][89][90] …”

Experimental and model research on chloride ion gas–solid distribution in the process of desulfurization wastewater evaporation

“…Yong H. Huang explored the removal performance of heavy metals in desulfurization wastewater using hybrid zerovalent iron. 7,8 The results revealed that the removal efficiencies of Se and Hg were more than 99%; Lin Cui studied electrolysis-electrodialysis process removing chloride ion from wet ue gas desulfurization wastewater and the removal efficiency reached 83.3%; 9 Na Yin investigated the process feasibility of ultraltration-nanoltration-reverse osmosis applying for desulfurization wastewater treatment, which could produce sulfuric acid and ammonium salt at the same time, results showed that the process could treat desulfurization wastewater to the discharge standard and the by-product purity was high. 10 On April 16, 2015, the State Council of China issued the "Water Pollution Control Action Plan", to emphasize the management of various types of water pollution.…”