Continuous removal of heavy metals from FGD wastewater in a fluidised bed without sludge generation

A patent pending fluid-bed process has been developed by Krüger for removal of dissolved heavy metals by adsorption/coprecipitation. The waste product is a very compact granulate with a very low water content of 10-20%. Sludge is not produced. The fluid-bed technique was tested at a coal-fired power station with wastewater from the flue gas desulphurisation (FGD) unit for removal of heavy metals from the wastewater. By dosing only potassium permanganate to the wastewater, the content of dissolved nickel, cadmium and zinc was reduced by respectively 99%, 92% and 97% at optimum treatment in one fluid-bed reactor. The weight of waste product produced will constitute less than 25% of the waste product produced by the present traditional chemical precipitation. Chemical costs are approximately 0.6 US$/m³ which are similar for the fluid-bed and present wastewater treatment processes.