Management of Flue Gas Desulfurization Wastewater Residuals from Zero Liquid Discharge Systems from the Coal-Fired Power Industry

Abstract

The safe disposal of FGD brines is a new environmental challenge facing the coal-fired power industry. Due to the removal of heavy metals from coal combustion flue gas in wet FGD units, the purge brines from these units contain significant concentrations of arsenic, cadmium, chromium, mercury, and selenium. The USEPA is currently revising the Steam Electric Power Generation Effluent Guidelines, where it is expected that discharge limits for metals could be made much more stringent. In addition, the new regulations could limit co-mingling of wastewater streams (such as FGD purge brines and cooling tower blowdown). Treatment of FGD purge brines has gained traction in the industry due to being the main source of the discharge of metals in power plant waters. Among various treatment options for FGD brines, zero liquid discharge (ZLD) approaches are gaining significant interest from the industry because traditional physical, chemical or biological treatments may be cost prohibitive and unreliable to meet the new limits. ZLD transforms the challenge presented by the brines from wastewater treatment to a solid waste disposal issue.