Pilot Demonstration of the Activated Iron Process for Removing Heavy Metals from Flue-Gas-Desulfurization (FGD) Wastewater

Abstract

The Activated Iron Process (AIP), a novel chemical water treatment platform, was developed for removing various micro-pollutants and impurities from a liquid stream. This integrated treatment system employs certain iron chemistry to create a hybridized reactive solid mixture that comprises three reactive components: zero-valent iron (ZVI) particles with activated surface, redox reactive iron oxide crystalline (FeOx), and certain labile Fe(II) species. The hybrid ZVI/FeOx/Fe(II) system can overcome the surface passivation problem of a conventional ZVI system, providing sustainable reactive power from the activated irons to react, transform, precipitate, and mineralize various heavy metals and nutrients from wastewater.In this study, a pilot-scale AIP prototype capable of treating 2 gpm was demonstrated in a fivemonth continuous-flow test at a power plant. The treatment system accepted raw FGD wastewater, reduced all major pollutants of concern and produced a high quality effluent. The system consistently reduced total mercury (Hg), mostly in dissolved form, from about 100 µg/L to below 0.010 µg/L. Total selenium (Se), of which most was selenate, was decreased from about 2,000 µg/L to below 10 µg/L. Nitrate was lowered from 10-25 mg/L to below 0.2 mg/L. Moreover, the AIP system achieved high reduction for many other heavy metals; e.g., arsenic (As), cadmium (Cd), chromium (Cr), nickel (Ni), lead (Pb), zinc (Zn), and copper (Cu) were all rapidly reduced from 1-5 mg/L level to near or below 1 µg/L in a control spike test. The process uses inexpensive iron based chemicals and produces a limited amount of solid waste.This advanced technology can be commercialized to provide a cost-effective and reliable solution to the FGD wastewater and other metal-contaminated waste streams in various industries. This technology can help industries meet the most stringent effluent discharge regulations for heavy metals and nutrients. KEYWORDS activated iron process, zero-valent iron, hZVI, FGD wastewater, heavy metals, selenium removal, mercury removal 7134 WEFTEC 2012

Review of Migration, Transformation, and Control of Volatile Components during Desulfurization Wastewater Evaporation: Advances and Perspectives

“…(b) Pretreatment : Conventional treatment processes such as the zerovalent iron and adsorption methods have been investigated in FGD wastewater treatment. Huang et al , integrated zerovalent iron, magnetite, and divalent iron materials, designed a four-stage composite zerovalent iron reactor for FGD wastewater treatment, and then tested the removal of Hg and Se on a 5-month-long pilot platform. The effluent results showed that the technology could control Hg and Se below 10 μg/L and 10 ng/L.…”

“…(b) Pretreatment: Conventional treatment processes such as the zerovalent iron and adsorption methods have been investigated in FGD wastewater treatment. Huang et al 131,132 effluent results showed that the technology could control Hg and Se below 10 μg/L and 10 ng/L. Zhu 133 prepared a magnetic zeolite mercury adsorbent using iron ore from activated fly ash, and the adsorbent achieved 92% Hg 2+ removal under adsorption conditions with a solid-to-liquid ratio of 5 g/L and initial pH of 5.…”

Removal of Mercury from Simulated Flue Gas Desulfurization Wastewater using Functionalized Silica

“…A detailed knowledge of the original coal composition is crucial for determining the concentrations of toxic metal cations in the FGD wastewater. The biggest challenge for the electric utility industry is to develop more advanced treatment methods in order to reduce the concentrations of heavy metal cations present in a complex FGD matrix to permissible levels [8].…”