Bacteria immobilsation on hydroxyapatite surface for wastewater treatment

Heavy metals pollution in the environment is a big cause of concern, due to the toxicity of the metals themselves. In this work we propose an innovative method for heavy metals removal from contaminated waste water – a combination of hydroxyapatite (already used for water treatment) and microorganisms. Selected bacterial strains were immobilised on the surface of hydroxyapatite of natural origin (extracted from cod fish bones). These systems were used to tested on heavy metals, such as zinc and cadmium, from water solutions. The three strains used were Pseudomonas fluorescens, Microbacterium oxydans and Cupravidus sp.; they were selected as they showed high heavy metal resistance. SEM micrographies were used to study their immobilization on the hydroxyapatite surface. Solutions containing different concentrations of either Zn (II), Cd (II) or both metals at the same time were used. Results showed that the combination of hydroxyapatite and bacteria increases the metal uptake, indicating a synergistic action between the solid support and the bacteria biofilm. Particularly high removal rates were observed for higher heavy metal concentrations and for the Pseudomonas fluorescens strain. This work shows a promising way for environmental remediation, combining products of natural origin with microbiology.