The OZONE4WATER project aims at developing a disruptive ozone-technology for water/wastewater treatment. The new technology will help change the current panorama of ozone-based water treatment solutions by tackling the lack of ozone generators able to produce gas streams rich in ozone, and of contacting reactors with improved gas-liquid mass transfer. Ultimately, this will lead to lower energy consumption for ozone production, and to overcome the need for large contacting reactors and extended contacting times.
Regarding Task 1, the laboratory prototype for O2/O3 separation using functionalized membranes is now completed
Within Task 2, the overall volumetric gas/liquid mass transfer coefficients for the static mixer NETmix (1 paper under preparation) and tubular membrane contactor (2 papers published), considering different operational conditions, were determined experimentally and validated by CFD modelling. Furthermore, a model to describe the two-phase pressure drop in the multiphase flow was proposed for the NETmix and tested with numerical data (1 paper submitted).
In Task 3, the low footprint ozone side stream contacting train laboratory prototype, integrating the static mixer NETmix, and reaction chamber was already designed and is under construction.
Regarding Task 4, a conventional NETmix and membrane contactor, coupled to a reaction column, was applied for the tertiary treatment of urban wastewater (UWW), targeting disinfection and contaminants of emerging concern (CECs) removal. Urban wastewater after secondary treatment (activated sludge biological process) was spiked with 19 CECs (10 µg/L each) selected under NOR-WATER project. Using the membrane contactor, for an O3 dose of 18 g m-3, the best performance was obtained by increasing the O3 concentration (maximum [O3]G,inlet of 200 g Nm-3) and decreasing the gas flow rate (minimum QG of 0.15 Ndm3 min-1), providing the highest ozone transfer yield (88%) and, thus higher specific ozone dose (g O3 per g dissolved organic carbon). Under these conditions, removals >80% or concentrations below the limit of quantification were obtained for up to 13 of the 19 CECs and reductions up to 5 log units for total heterotrophs and below the limit of detection for enterobacteria and enterococci. Tests including a UVC dose of 0.10 kJ L-1 enhanced disinfection ability but had no impact on CECs oxidation. After ozonation, the abundance of antibiotic resistant bacteria was reduced but not eliminated and microbial regrowth after 3-day storage was observed. No toxic effect was detected on zebrafish embryos using a dilution factor of 4 for the ozonized UWW and when granular activated carbon adsorption was subsequently applied the dilution factor decreased to 2. The same system proved again to be very efficient, with >90% removal for 12 of 14 antibiotics (18 mg O3 L-1). UHPLC-QTOF-HRMS tentatively identified seven by-products stemming from macrolides for O3 treatment. Tests with the NETmix showed its potential to provide an O3-rich stream required for the CECs oxidation in the contact/reaction column. An O3 dose of 18 gO3 m-3 ([O3]G = 60 g Nm-3) and a hydraulic retention time (HRT) of 54 s resulted in removal values above 80% for 7 of 19 CECs in UWW. Further studies are being carried out with an urban wastewater after secondary treatment using a membrane biological reactor. In the next months, the low footprint ozone side stream contacting train laboratory prototype will be installed in the water treatment plant of Lever, to evaluate its performance in the pre-oxidation of surface water for human consumption. Afterwards, the same prototype will be installed in the wastewater treatment plant of Ave, to evaluate its performance in the tertiary treatment of urban wastewaters targeting CECs removal. |
