Heavy metals removal from waste water by moving bed sand filters inoculated with heavy metal adsorbing or precipitating micro-organisms

The ultimate cleaning of heavy metal containing wastewater to metal concentrations below 0.1 ppm is difficult to achieve with economically acceptable physico-chemical techniques. The use of metal-sorbing or -bioprecipitating biomass offers such possibilities. However the efficiency depends of the biomass concentration and the regeneration of the biomass gives certain drawbacks. Therefore in this new application growing biomass is used in stead of dead biomass. For the removal of these low metal concentrations a special biotechnological method was developed with the objective the generation of a sludge which can be processed in a pyrometallurgical proces. The MERESAFIN (MEtal REmoval by SAndFilter INoculation) system is based on the inoculation of a sandfilter with metal biosorhing or bioprecipitating bacteria. In order to do so AstraSand filters are inoculated with metal-biosorbing or -bioprecipitating micro-organisms. After filtration of the metal bearing wastewater, the biomass, forming a film on the filtration material, will contain high metal concentrations. Via a mechanical washing system this metal loaded biomass will be removed and leave a clean thin biofilm on the filtration material for reuse. The metals will be recycled by a pyrometallurgical treatment of the metal containing sludge in a shaft furnace. This process will allow a final polishing of metal contaminated wastewater in an economically acceptable way and without production of an extra waste stream. Results wi II be presented from lab experiments as well as from a pilot treating 30 m(3)/h with complete removal of Co, Ni, Cu and Zn. Also nitrates and COD can be removed. Results on metal removal from different waters and processing of metal loaded sludge will be presented.