Ilse Forrez

Diclofenac Oxidation by Biogenic Manganese Oxides

Diclofenac, a nonsteroidal anti-inflammatory drug, is one of the most commonly detected pharmaceuticals in sewage treatment plant (STP) effluents. In this work, biologically produced manganese oxides (BioMnOx) were investigated to remove diclofenac. At neutral pH, the diclofenac oxidation with BioMnOx was 10-fold faster than with chemically produced MnO(2). The main advantage of BioMnOx over chemical MnO(2) is the ability of the bacteria to reoxidize the formed Mn(2+), which inhibits the oxidation of diclofenac. Diclofenac-2,5-iminoquinone was identified as a major transformation product, accounting for 5-10% of the transformed diclofenac. Except for 5-hydroxydiclofenac, which was identified as an intermediate, no other oxidation products were detected. Diclofenac oxidation was proportional to the amount of BioMnOx dosed, and the pseudo first order rate constant k was 6-fold higher when pH was decreased from 6.8 to 6.2. The Mn(2+) levels remained below the drinking water limit (0.05 mg L(-1)), thus indicating the efficient in situ microbiological regeneration of the oxidant. These results combined with previous studies suggest the potential of BioMnOx for STP effluent polishing.

Biogenic metals for the oxidative and reductive removal of pharmaceuticals, biocides and iodinated contrast media in a polishing membrane bioreactor

Pharmaceutical and personal care products, biocides and iodinated contrast media (ICM) are persistent compounds, which appear in ng to μg L(-1) in secondary effluents of sewage treatment plants (STPs). In this work, biogenic metals manganese oxides (BioMnOx) and bio-palladium (Bio-Pd) were applied in lab-scale membrane bioreactors (MBR) as oxidative and reductive technologies, respectively, to remove micropollutants from STP-effluent. From the 29 substances detected in the STP-effluent, 14 were eliminated in the BioMnOx-MBR: ibuprofen (>95%), naproxen (>95%), diuron (>94%), codeine (>93%), N-acetyl-sulfamethoxazole (92%), chlorophene (>89%), diclofenac (86%), mecoprop (81%), triclosan (>78%), clarithromycin, (75%), iohexol (72%), iopromide (68%), iomeprol (63%) and sulfamethoxazole (52%). The putative removal mechanisms were the chemical oxidation by BioMnOx and/or the biological removal by Pseudomonas putida and associated bacteria in the enriched biofilm. Yet, the removal rates (highest value: 2.6 μg diclofenac L(-1) d(-1)) need to improve by a factor 10 in order to be competitive with ozonation. ICM, persistent towards oxidative techniques, were successfully dehalogenated with a novel reductive technique using Bio-Pd as a nanosized catalyst in an MBR. Iomeprol, iopromide and iohexol were removed for >97% and the more recalcitrant diatrizoate for 90%. The conditions favorable for microbial H(2)-production enabling the charging of the Pd catalyst, were shown to be important for the removal of ICM. Overall, the results indicate that Mn oxide and Pd coupled to microbial catalysis offer novel potential for advanced water treatment.

Removal of diatrizoate with catalytically active membranes incorporating microbially produced palladium nanoparticles.

There is an increasing concern about the fate of iodinated contrast media (ICM) in the environment. Limited removal efficiencies of currently applied techniques such as advanced oxidation processes require more performant strategies. The aim of this study was to establish an innovative degradation process for diatrizoate, a highly recalcitrant ICM, by using biogenic Pd nanoparticles as free suspension or immobilized in polyvinylidene fluoride (PVDF) and polysulfone (PSf) membranes. As measured by HPLC-UV, the removal of 20mg L(-1) diatrizoate by a 10mg L(-1) Pd suspension was completed after 4h at a pH of 10. LC-MS analysis provided evidence for the sequential hydrodeiodination of diatrizoate. Pd did not lose its activity after incorporation in the PVDF and PSf matrix and the highest activity (k(cat)=30.0+/-0.4h(-1) L g(-1) Pd) was obtained with a casting solution of 10% PSf and 500mg L(-1) Pd. Subsequently, water containing 20mg L(-1) diatrizoate was treated in a membrane contactor, in which the water was supplied at one side of the membrane while hydrogen was provided at the other side. In a fed batch configuration, a removal efficiency of 77% after a time period of 48h was obtained. This work showed that membrane contactors with encapsulated biogenic nanoparticles can be instrumental for treatment of water contaminated with diatrizoate.

Influence of manganese and ammonium oxidation on the removal of 17α-ethinylestradiol (EE2)

Flow-through reactors with manganese oxides were examined for their capacity to remove 17 alpha-ethinylestradiol (EE2) at microg L(-1) and ng L(-1) range from synthetic wastewater treatment plant (WWTP) effluent. The mineral MnO(2) reactors removed 93% at a volumetric loading rate (B(V)) of 5 microg EE2 L(-1) d(-1) and from a B(V) of 40 microg EE2 L(-1) d(-1) on, these reactors showed 75% EE2 removal. With the biologically produced manganese oxides, only 57% EE2 was removed at 40 microg EE2 L(-1) d(-1). EE2 removal in the ng L(-1) range was 84%. The ammonium present in the influent (10 mg N L(-1)) was nitrified and ammonia-oxidizing bacteria (AOB) were found to be of prime importance for the degradation of EE2. Remarkably, EE2 removal by AOB continued for a period of 4 months after depleting NH(4)(+) in the influent. EE2 removal by manganese-oxidizing bacteria was inhibited by NH(4)(+). These results indicate that the metabolic properties of nitrifiers can be employed to polish water containing EE2 based estrogenic activity.

Manganese‐oxidizing bacteria mediate the degradation of 17α‐ethinylestradiol

Manganese (II) and manganese‐oxidizing bacteria were used as an efficient biological system for the degradation of the xenoestrogen 17α‐ethinylestradiol (EE2) at trace concentrations. Mn2+‐derived higher oxidation states of Mn (Mn3+, Mn4+) by Mn2+‐oxidizing bacteria mediate the oxidative cleavage of the polycyclic target compound EE2. The presence of manganese (II) was found to be essential for the degradation of EE2 by Leptothrix discophora, Pseudomonas putida MB1, P. putida MB6 and P. putida MB29. Mn2+‐dependent degradation of EE2 was found to be a slow process, which requires multi‐fold excess of Mn2+ and occurs in the late stationary phase of growth, implying a chemical process taking place. EE2‐derived degradation products were shown to no longer exhibit undesirable estrogenic activity.

Biodegradation of micropollutants and prospects for water and wastewater biotreatment

Sewage treatment plants (STPs) are the main pollution source of micropollutants, including pharmaceuticals and personal care products (PPCPs). Understanding the biotreatment processes of domestic and hospital wastewaters is important for the optimization of micropollutant degradation at the discharge source in order to decrease their concentrations and associated biological effects. It is known that a large group of compounds comprising aliphatic, aromatic, and halogenated molecules are co-metabolized during nitrification by the enzyme ammonia monooxygenase (AMO). Therefore, the use of autotrophic processes, such as nitrification, to decrease the micropollutant burden on surface waters by removing biological effects, such as estrogenicity, could be an opportunity for trace compounds remediation.

Bioaugmentation to degrade the organic de-icers acetate and monopropylene glycol at low temperatures

Two de-icers, potassium acetate and monopropylene glycol (MPG), used widespread as a runway and wing de-icer respectively, can exert high BOD in the surrounding waters. A bioaugmentation approach to degrade these de-icer compounds in the drainage water prior to discharge has been tested. A microbial consortium originating from soil was enriched at low temperatures (4 degrees C) in order to adapt to wintertime conditions. With 0.05 g CDW/L of biocatalyst, maximum specific removal rates up to 1.46 and 3.33 g acetate/g CDW d at 4 degrees C were achieved with and without biostimulation respectively. An acetate:MPG mixture of 1:3 at a total COD concentration of 0.80 and 1.20 g/L was degraded in 12 days by 83 and 70% respectively. Bioaugmentation in the field over a period of 25 days showed a removal of 88% MPG compared to 46% in the control. These results demonstrate that bioaugmentation of airport runoff water can be successfully applied to prevent organic de-icer compounds from entering the receiving surface waters.