Wastewater treatment by bio-magnetic separation: A comparison of iron oxide and iron sulphide biomass recovery

Many microorganisms have an affinity to accumulate metal ions onto their surfaces, which results in metal loading of the biomass. Microbial biomineralisation of iron produces a biomass, which is often highly magnetic and can be separated from water systems by the application of a magnetic field. This paper reports on the magnetic separation of biomass containing microbial iron oxide (Fe3O4 present within magnetotactic bacteria) and iron sulphide (Fe1-xS, precipitated extracellularly by sulphate reducing bacteria) in a single wire cell. Since such bacteria can be separated magnetically, their affinity to heavy metal or organic material accumulation renders them useful for the removal of pollutants from wastewater. The relative merits of each bacterium to magnetic separation techniques in terms of applied magnetic field and processing conditions are discussed. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.