Degradation of phenanthrene and fluoranthene in a slurry bioreactor using free and Ca-alginate-immobilized Sphingomonas pseudosanguinis and Pseudomonas stutzeri bacteria

Abstract

Biodegradation studies of three- and four-ring polycyclic aromatic hydrocarbons (PAHs) (phenanthrene [PHE] and fluoranthene [FLU]) were conducted using free and Ca-alginate-immobilized Sphingomonas pseudosanguinis strain J1-q (S1) and Pseudomonas stutzeri strain (S2) in bench-scale sediment slurry reactors. In this study, the effects of sodium alginate (SA) dosage on the characteristics of immobilized bacterial beads were investigated. The results indicated a 3% alginate concentration was optimal for immobilizing bacteria for PHE and FLU degradation. Scanning electron microscopy (SEM) images of the immobilized beads showed the presence of honeycomb structures and abundant interstices in the beads, which provided adequate space for microorganism adhesion and proliferation. The biodegradation of PHE and FLU using both free and immobilized bacteria fit a first-order reaction model well. The degradation efficiencies of PHE and FLU using immobilized bacteria were higher than those of free bacteria in sediment slurry reactors. The removal percentages of PHE and FLU using immobilized indigenous bacteria strain S1 after 42 d were 63.16% and 56.94%, respectively, which were higher than the removal percentages of exogenous strain S2.

Keywords: Biodegradation; Fluoranthene; Immobilization; Phenanthrene; Sediment.