Fungal removal of OPFRs from urban wastewater in a rotary drum bioreactor

Organophosphate flame retardants (OPFRs) removal is usually limited in conventional treatment systems. This study assessed the long-term removal of five OPFRs (TBP, TBEP, TCEP, TCPP and TEP) in wastewater using rotating drum bioreactors (RDBs) inoculated with a white-rot fungi (WRF) consortium (Trametes versicolor, Ganoderma lucidum, Pycnoporus sanguineus). Fungi were immobilized on holm oak wood or polylactic acid (PLA) and four RDBs were operated over six batch cycles: two PLA-supported reactors (one supplemented with glucose), one WRF-inoculated wood reactor (W-Exp), and one wood-only control (W-Cont). TEP showed negligible removal, while more than 90% of TBP and TBEP were removed in all reactors. Sorption studies in wood reactors indicated TBP and TBEP were mostly degraded by native microorganisms, while chlorinated OPFRs were degraded only in the W-Exp (removal of 57% for TCEP and 68% for TCPP, from which 40% and 65% respectively, were degraded). Previously proposed degradation pathways were confirmed, and potentially toxic intermediates disappeared over time, yielding a non-toxic effluent. G. lucidum showed a three-log growth increase in the W-Exp reactor, likely emerging as the main species responsible for chlorinated OPFRs degradation. PLA supported fungal colonization but limited growth, and glucose addition hindered performance. Finally, the established microbial community in the W-Exp reactor achieved almost complete degradation of sorbed OPFRs as a post-treatment alternative for wood residues. These results demonstrate the efficiency of wood-supported WRF systems for OPFRs removal under real, non-sterile conditions.