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

摘要

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.