Peroxydisulfate activation by CuO pellets in a fixed-bed column, operating mode and assessments for antibiotics degradation and urban wastewater disinfection.

A fixed-bed column packed with copper oxide pellets (FBC-CuO) combined with peroxydisulfate (PDS) as a primary oxidant was assessed as an option for simultaneously wastewater decontamination (antibiotics) and disinfection (bacteria, viruses, and protozoa). Preliminary to these experiments, phenol was used as the target molecule to investigate the working mode of FBC-CuO under various operating conditions, such as varying flow rates, initial persulfate, and phenol concentrations. Then, the removal of a mix of five representative antibiotics (amoxicillin (AMX), cefalexin (CFX), ofloxacin (OFL), sulfamethoxazole (SMX), and clarithromycin (CLA)) in secondary treated urban wastewater (STWW) was evaluated. AMX, CFX, and OFL were effectively removed by simply flowing through the FBC-CuO, and the addition of PDS (500 µM) systematically enhanced the degradation of all targeted antibiotics, which is also the necessary condition for the removal of SMX and CLA. Urban wastewater disinfection was evaluated by monitoring targeted pathogens originally in the STWW. A significant reduction of Escherichia coli, Enterococcus, F-specific RNA bacteriophages was observed after the treatment by FBC-CuO with 500 µM PDS. X-ray diffraction measurement and scanning electron microscopy performed on CuO pellets before and after treatment confirmed that the structure of the catalyst was preserved without any phase segregation. Finally, quantification of Cu(II) at the outlet of FBC-CuO indicate a non-negligible but limited released. All these results underline the potential of the FBC-CuO combined with PDS at the field scale for the degradation of micropollutants and inactivation of pathogens in wastewater.

Copper oxide/peroxydisulfate system for urban wastewater disinfection: Performances, reactive species, and antibiotic resistance genes removal.

In this study, copper oxide (CuO) catalyzed peroxydisulfate (PDS) system was investigated for the inactivation of a broad range of pathogenic microorganisms from urban wastewater. Complete inactivation of Escherichia coli, Enterococcus, F-specific RNA bacteriophages from secondary treated wastewater was achieved after a short time (15-30 min) treatment with CuO (10 g/L)/PDS (1 mM) system, but spores of sulfite-reducing bacteria took 120 min. No bacterial regrowth occurred during storage after treatment. Significant reduction of the pathogens was explained by the generation of the highly selective Cu(III) oxidant, as the predominant reactive species, which could quickly oxidize guanine through a one-electron oxidation pathway. Additionally, the potential of the CuO (10 g/L)/PDS (1 mM) system to inactivate antibiotic-resistant bacteria and antibiotic resistance genes (ARB&Gs) was explored. Sulfamethoxazole-resistant E. coli was used as the model ARB and a 3.2 log of reduction was observed after 10 min of treatment. A considerable reduction (0.7-2.3 log) of selected ARGs including blaTEM, qnrS, emrB, sul1, and genes related to the dissemination of antibiotic resistance, including the Class 1 integron-integrase (intI1), and the insertion sequence (IS613) was achieved after 60 min treatment. All these findings indicated the promising applicability of the CuO/PDS system as a disinfection technology for wastewater reuse in agriculture.

Combining micelle-clay sorption to solar photo-Fenton processes for domestic wastewater treatment.

A tertiary treatment of effluent from a biological domestic wastewater treatment plant was tested by combining filtration and solar photocatalysis. Adsorption was carried out by a sequence of two column filters, the first one filled with granular activated carbon (GAC) and the second one with granulated nano-composite of micelle-montmorillonite mixed with sand (20:100, w/w). The applied solar advanced oxidation process was homogeneous photo-Fenton photocatalysis using peroxymonosulfate (PMS) as oxidant agent. This combination of simple, robust, and low-cost technologies aimed to ensure water disinfection and emerging contaminants (ECs, mainly pharmaceuticals) removal. The filtration step showed good performances in removing dissolved organic matter and practically removing all bacteria such as Escherichia coli and Enterococcus faecalis from the secondary treated water. Solar advanced oxidation processes were efficient in elimination of trace levels of ECs. The final effluent presented an improved sanitary level with acceptable chemical and biological characteristics for irrigation.

Biosensor-based real-time monitoring of paracetamol photocatalytic degradation.

This paper presents for the first time the integration of a biosensor for the on-line, real-time monitoring of a photocatalytic degradation process. Paracetamol was used as a model molecule due to its wide use and occurrence in environmental waters. The biosensor was developed based on tyrosinase immobilization in a polyvinylalcohol photocrosslinkable polymer. It was inserted in a computer-controlled flow system installed besides a photocatalytic reactor including titanium dioxide (TiO2) as photocatalyst. It was shown that the biosensor was able to accurately monitor the paracetamol degradation with time. Compared with conventional HPLC analysis, the described device provides a real-time information on the reaction advancement, allowing a better control of the photodegradation process.

Solar photo-Fenton using peroxymonosulfate for organic micropollutants removal from domestic wastewater: comparison with heterogeneous TiO2 photocatalysis.

This work aims at decontaminating biologically treated domestic wastewater effluents from organic micropollutants by sulfate radical based (SO4(-)) homogeneous photo-Fenton involving peroxymonosulfate as an oxidant, ferrous iron (Fe(II)) as a catalyst and simulated solar irradiation as a light source. This oxidative system was evaluated by using several probe compounds belonging to pesticides (bifenthrin, mesotrione and clothianidin) and pharmaceuticals (diclofenac, sulfamethoxazole and carbamazepine) classes and its kinetic efficiency was compared to that to the well known UV-Vis/TiO2 heterogeneous photocatalysis. Except for carbamazepine, apparent kinetic rate constants were always 10 times higher in PMS/Fe(II)/UV-Vis than in TiO2/UV-Vis system and more than 70% of total organic carbon abatement was reached in less than one hour treatment. Hydroxyl radical (OH) and SO4(-) reactivity was investigated using mesotrione as a probe compound through by-products identification by liquid chromatography-high resolution-mass spectrometry and transformation pathways elucidation. In addition to two OH based transformation pathways, a specific SO4(-) transformation pathway which first involved degradation through one electron transfer oxidation processes followed by decarboxylation were probably responsible for mesotrione degradation kinetic improvement upon UV-Vis/PMS/Fe(II) system in comparison to UVVis/TiO2 system.

Theoretical investigation of biomass productivities achievable in solar rectangular photobioreactors for the cyanobacterium Arthrospira platensis.

Modeling was done to simulate whole-year running of solar rectangular photobioreactors (PBRs). Introducing the concept of ideal reactor, the maximal biomass productivity that could be achieved on Earth on nitrate as N-source was calculated. Two additional factors were also analyzed with respect to dynamic calculations over the whole year: the effect of PBR location and the effects of given operating conditions on the resulting decrease in productivity compared with the ideal one. Simulations were conducted for the cyanobacterium Arthospira platensis, giving an ideal productivity (upper limit) in the range 55-60 tX ha(-1) year(-1) for a sun tracking system (and around 35-40 tX ha(-1) year(-1) for a fixed horizontal PBR). For an implantation in France (Nantes, west coast), the modification in irradiation conditions resulted in a decrease in biomass productivity of 40%. Various parameters were investigated, with special emphasis on the influence of the incident angle of solar illumination on resulting productivities, affecting both light capture and light transfer inside the bulk culture. It was also found that with appropriate optimization of the residence time as permitted by the model, productivities close to maximal could be achieved for a given location.