Biodegradation of Polyethoxylated Nonylphenols in Packed-Bed Biofilm Reactors

The opportunity to apply an immobilized-cell biotechnological process in the remediation of polyethoxylated nonylphenol (NP n EO) contaminated water was studied in this work. To this purpose, three identically configured aerobic column reactors packed with different materials (silica beads, granular activated carbon, or glass spheres) were developed, inoculated with the NP n EO-degrading Pseudomonas sp. strain BCb 12/3, and compared for their ability to biodegrade the two NP n EO industrial mixtures Igepal CO-520 and CO-210 fed in synthetic wastewater at concentrations in the range 30−90 mg/L. The three biofilm reactors, tested under batch conditions, showed comparable degradation capabilities and specificities, being able to remove from 77 to 99% of the total Igepal mixtures supplied after 9 days of batch treatment. NP n EOs were mostly removed through biodegradation, as suggested by the accumulation of two metabolites typical of NP n EO aerobic biodegradation, such as phenol and 4-nonylphenol, and by the low NP n EO amounts recovered from the reactors at the end of the study. Fluorescent in situ hybridization and DAPI staining performed at the end of the study showed that the bacterial biofilm was well and homogenously developed on the packed beds of the three reactors and that it was mostly composed by bacteria belonging to Gammaproteobacteria, i.e., the Proteobacteria class which includes the genus Pseudomonas .