Biodegradation of polyethoxylated nonylphenols in packed-bed biofilm reactors

The opportunity to apply immobilized-cell biotechnological process in the remediation of polyethoxylated nonylphenol (NPnEO)-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 NPnEO-degrading Pseudomonas sp. strain BCb 12/3 and compared for their ability to biodegrade the two NPnEO industrial mixtures Igepal CO-520 and CO-210 applied through a synthetic wastewater at concentrations in the range 30÷90 mg/L. The 3 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. NPnEOs were mostly removed through biodegradation, as suggested by the accumulation of two metabolites typical of NPnEO aerobic biodegradation, such as phenol and 4-nonylphenol and by the low NPnEO 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 3 reactors and that it was mostly composed by bacteria belonged to Gammaproteobacteria, i.e. the Proteobacteria class which includes the genus Pseudomonas.