Removal and environmental risk assessment of contaminants of emerging concern from irrigation waters in a semi-closed microalgae photobioreactor

The present study evaluated the efficiency of a semi-closed, tubular, horizontal photobioreactor (PBR) to treat a mixture of irrigation and rural drainage water, focusing in the removal of different contaminants of emerging concern (CECs), and evaluating the environmental impact of the resulting effluent. Target CECs included pharmaceuticals, personal care products and flame retardants. Of the 13 compounds evaluated, 11 were detected in the feed water entering the PBR, and diclofenac (DCF) (1107 ng L^-1) and N,N-diethyl-toluamide (DEET) (699 ng L^-1) were those present at the greatest concentrations. The best removal efficiencies were achieved for the pharmaceuticals diazepam (94%), lorazepam (LZP) (83%) and oxazepam (OXA) (71%), and also for ibuprofen (IBU) (70%). For the rest of the CECs evaluated, attenuation was similar to that obtained after conventional wastewater treatment, ranging from basically no elimination (carbamazepine (CBZ) and tris-(2-chloroethyl) phosphate (TCEP)) to medium efficiencies (DCF and tributyl phosphate (TBP) (50%)). Environmental risk assessment based on hazard quotients (HQs) resulted in HQ values < 0.1 (no risk associated) for most of the compounds and most of the trophic levels considered. Values between 1 and 10 (moderate risk) were obtained for tonalide (AHTN) (fish) and CBZ (invertebrates). The most sensitive trophic level was green algae, whereas fish and aquatic plants were the most resilient. Our results suggest that microalgae-based treatments could become a green, cost-effective alternative to conventional wastewater treatment regarding the efficient elimination of these contaminants.

UV/H2O2degradation of the antidepressants venlafaxine and O-desmethylvenlafaxine: Elucidation of their transformation pathway and environmental fate

The aim of the present work is to investigate the removal and transformation of the antidepressants venlafaxine (VFX) and its main metabolite O-desmethylvenlafaxine (DVFX) upon advanced oxidation with UV/H2O2 under lab conditions. High-resolution mass spectrometry (HRMS) analyses were carried out by means of ultra-high pressure liquid chromatography (UHPLC)-linear ion trap high resolution Orbitrap instrument (LTQ-Orbitrap-MS) in order to elucidate the different transformation products (TPs) generated. The depletion of both VFX and DVFX was very significant, with the 99.9% of both compounds eliminated after 5 and 30 min of reaction, respectively. Eleven TPs for VFX and six for DVFX were detected and their molecular structures elucidated by means of MS(2) and MS(3) scans, and the corresponding degradation pathways were proposed. The combined ecotoxicity at different treatment times was evaluated by means of bioluminescence inhibition assays with the marine bacteria Vibrio fischeri. Results showed an increase in the ecotoxicity during the UV/H2O2 experiment, especially at those reaction times where the total abundance of TPs was higher.

Advanced oxidation of the antibiotic sulfapyridine by UV/H₂O₂: Characterization of its transformation products and ecotoxicological implications

The aim of the present work is to investigate, under lab-scale conditions, the removal and transformation of the antibiotic sulfapyridine (SPY) upon advanced oxidation with UV/H2O2. High resolution mass spectrometry (HRMS) analyses by means of an ultra-high pressure liquid chromatography (UHPLC)-linear ion trap high resolution Orbitrap instrument (LTQ-Orbitrap-MS) were carried out in order to elucidate the different transformation products (TPs) generated. The abatement (>99%) of the antibiotic was only achieved after 180 min, highlighting its resilience to elimination and its potential persistence in the environment A total of 10 TPs for SPY were detected and their molecular structures elucidated by means of MS(2) and MS(3) scans. Finally, the combined ecotoxicity at different treatment times was evaluated by means of bioluminescence inhibition assays with the marine bacteria Vibrio fischeri.

Biodegradation of sulfamethazine by Trametes versicolor: Removal from sewage sludge and identification of intermediate products by UPLC-QqTOF-MS

Degradation of the sulfonamide sulfamethazine (SMZ) by the white-rot fungus Trametes versicolor was assessed. Elimination was achieved to nearly undetectable levels after 20 h in liquid medium when SMZ was added at 9 mg L(-1). Experiments with purified laccase and laccase-mediators resulted in almost complete removal. On the other hand, inhibition of SMZ degradation was observed when piperonilbutoxide, a cytochrome P450-inhibitor, was added to the fungal cultures. UPLC-QqTOF-MS analysis allowed the identification and confirmation of 4 different SMZ degradation intermediates produced by fungal cultures or purified laccase: desulfo-SMZ, N4-formyl-SMZ, N4-hydroxy-SMZ and desamino-SMZ; nonetheless SMZ mineralization was not demonstrated with the isotopically labeled sulfamethazine-phenyl-13C6 after 7 days. Inoculation of T. versicolor to sterilized sewage sludge in solid-phase systems showed complete elimination of SMZ and also of other sulfonamides (sulfapyridine, sulfathiazole) at real environmental concentrations, making this fungus an interesting candidate for further remediation research.