Organophosphate flame retardants (OPFRs) are high-production volume chemicals widely present in environmental compartments. The presence of water-soluble OPFRs (tri-n-butyl phosphate (TnBP), tris(2-butoxyethyl) phosphate (TBEP), tris(2-chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCPP), and triethyl phosphate (TEP)) in water compartments evidences the struggle of conventional wastewater treatment plants (WWTPs) to effectively eliminate these toxic compounds. This study reports for the first time the use of white-rot fungi as a promising alternative for the removal of these OPFRs. To accomplish this, a simple and cost-efficient quantification method for rapid monitoring of these contaminants’ concentrations by GC–MS while accounting for matrix effects was developed. The method proved to be valid and reliable for all the tested parameters. Sample stability was examined under various storage conditions, showing the original samples to be stable after 60 days of freezing, while post-extraction storage techniques were also effective. Finally, a screening of fungal degraders while assessing the influence of the glucose regime on OPFR removal was performed. Longer chain organophosphate flame retardants, TBP and TBEP, could be easily and completely removed by the fungus Ganoderma lucidum after only 4 days. This fungus also stood out as the sole organism capable of partially degrading TCEP (35% removal). The other chlorinated compound, TCPP, was more easily degraded and 70% of its main isomer was removed by T. versicolor. However, chlorinated compounds were only partially degraded under nutrient-limiting conditions. TEP was either not degraded or poorly degraded, and it is likely that it is a transformation product from another OPFR’s degradation. These results suggest that degradation of chlorinated compounds is dependent on the concentration of the main carbon source and that more polar OPFRs are less susceptible to degradation, given that they are less accessible to radical removal by fungi. Overall, the findings of the present study pave the way for further planned research and a potential application for the degradation of these contaminants in real wastewaters. Graphical Abstract

Conventional polluted groundwater remediation struggles with persistent metal(loid)s, creating a need for integrated bioelectrochemical systems (BESs) and phytoremediation. The proposed configuration consisted of two sequential BESs, a microbial fuel cell (MFC) followed by a microbial electrolysis cell (MEC), whose treated effluent and exhausted anolyte were subsequently polished in individual subsurface vertical-flow macrophyte mesocosms (VFMMs), planted either with Phragmites australis, Scirpus holoschoenus, or Typha angustifolia. The overall treatment period was 38 days, comprising 8 days of BES treatment followed by 30 days of VFMM treatment. With MFC-MEC pretreatment, an overall 91% metal(loid) removal efficiency (RE) was noted, with REs of >99% for Fe and Cu, and between 71% and 92% for Al, Ni, Zn, Cd, and As, significantly increasing groundwater pH from 2.66 to 4.65, at p < 0.05. Macrophyte mesocosms, notably with P. australis and S. holoschoenus, further reduced residual Cu, Cd, Zn, and As levels below Flemish groundwater sanitation standards, nutrient concentrations and ecotoxicity (as demonstrated by Aliivibrio fischeri bioluminescence assays). Residual Ni was reduced by >99.9% but remained above regulatory thresholds. BES–phytoremediation sequential integration proved to be an effective biotreatment that combines the rapid contaminant removal capacity of BES with the polishing and ecological stabilization functions of constructed wetlands.

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.