Biotreatment of Cr(VI) and pyrene combined water pollution by loofa-immobilized bacteria

Hexavalent chromium (Cr(VI)) and pyrene are toxic pollutants that are difficult to remediate from soils and wastewater. Serratia sp. strains have been previously demonstrated to remove either Cr(VI) or pyrene and here a new isolate, called the Z6 strain, was demonstrated to remove both simultaneously. The removal occurs primarily by Cr(VI) reduction and pyrene biodegradation, and genome analysis suggests the removal mechanisms are the putative chromate reductase and two assumable pathways of pyrene degradation. The Z6 strain effectively removed most Cr(VI) (up to approximately 86%) and pyrene (up to approximately 57%) in seven different types of wastewater after 7 days of biotreatment. Additionally, the carrier loofa used for bacteria immobilization did not change the kinetics of Cr(VI) reduction or pyrene degradation. The carrier loofa was also effective for multiple uses, with removal capacity not being significantly affected over the first seven cycles with the same carrier loofa. These results provide data for developing practical biotreatment applications of Cr(VI) and pyrene contaminated sites.