Considerations for application of biosorption technology to remediate metal-contaminated industrial effluents

Inorganic contaminants present in waste streams may be removed by one of three methods, viz. physical, chemical or biological. Chemical and physical techniques have traditionally been employed to remediate such streams. However, due to the crisis of rapidly deteriorating potable water quality, legislation governing the levels of contaminants is becoming progressively stricter. Therefore, alternative methods for treatment have been investigated. Biosorption technology, utilising any natural form of biomass to passively adsorb and immobilise solubilised heavy metals or radionuclides, offers such an alternative. However, the technology needs to effectively compete both on a cost and performance basis with existing methods before industry will accept and implement it. A pilot-plant feasibility study, using waste activated sludge to bioremediate a metal plating effluent, showed that the currently used method of chemical precipitation is more cost-effective. This paper describes the factors that must be considered when selecting bioremediation as a cleanup technology for inorganics.