Multi-target assessment of advanced oxidation processes-based strategies for indirect potable reuse of tertiary wastewater: Fate of compounds of emerging concerns, microbial and ecotoxicological parameters.

Two advanced oxidation processes (AOPs), namely ozone/H2O2 and UV/H2O2, were tested at pilot scale as zero-liquid-discharge alternative treatments for the removal of microbiological (bacteria and viruses), chemical (compounds of emerging concern (CECs)) and genotoxic responses from tertiary municipal wastewater for indirect potable reuse (IPR). The AOP treated effluents were further subjected to granular activated carbon (GAC) adsorption and UV disinfection, following the concept of multiple treatment barriers. As a reference, a consolidated advanced wastewater treatment train consisting of ultrafiltration, UV disinfection, and reverse osmosis (RO) was also employed. The results showed that, for the same electrical energy applied, the ozone/H2O2 treatment was more effective than the UV/H2O2 treatment in removing CECs. Specifically, the ozone/H2O2 treatment, intensified by high pressure and high mixing, achieved an average CECs removal efficiency higher than UV/H2O2 (66.8% with respect to 18.4%). The subsequent GAC adsorption step, applied downstream the AOPs, further improved the removal efficiency of the whole treatment trains, achieving rates of 98.5% and 96.8% for the ozone/H2O2 and UV/H2O2 treatments, respectively. In contrast, the ultrafiltration step of the reference treatment train only achieved a removal percentage of 22.5%, which increased to 99% when reverse osmosis was used as the final step. Microbiological investigations showed that all three wastewater treatment lines displayed good performance in the complete removal of regulated and optional parameters according to both national and the European Directive 2020/2184. Only P. aeruginosa resulted resistant to all treatments with a higher removal by UV/H2O2 when higher UV dose was applied. In addition, E. coli STEC/VTEC and enteric viruses, were found to be completely removed in all tested treatments and no genotoxic activity was detected even after a 1000-fold concentration. The obtained results suggest that the investigated treatments are suitable for groundwater recharge to be used as a potable water source being such a procedure an IPR. The intensified ozone/H2O2 or UV/H2O2 treatments can be conveniently incorporated into a multi-barrier zero-liquid-discharge scheme, thus avoiding the management issues associated with the retentate of the conventional scheme that uses reverse osmosis. By including the chemical cost associated with using 11-12 mg/L of H2O2 in the cost calculations, the overall operational cost (energy plus chemical) required to achieve 50% average CECs removal in tertiary effluent for an hypothetical full-scale plant of 250 m3/h (or 25,000 inhabitants) was 0.183 €/m3 and 0.425 €/m3 for ozone/H2O2 and UV/H2O2 treatment train, respectively.

Optimal integration of vacuum UV with granular biofiltration for advanced wastewater treatment: Impact of process sequence on CECs removal and microbial ecology.

This study explored process synergies attainable by integrating a vacuum ultraviolet-based advanced oxidation process with biofiltration. A comparison using granular activated carbon or granular zeolite as filtration media were examined in context of advanced wastewater treatment for potable reuse. Six biofiltration columns, three with granular activated carbon and three with granular zeolite, were operated in parallel and batch-fed daily with nitrified secondary effluent. After achieving a pseudo-steady state through the filter columns, vacuum ultraviolet treatment was applied as pre-treatment or as post-treatment, at two different applied energies (i.e., VUV-E1=1 kWh/m3 and VUV-E10=10 kWh/m3). Once granular activated carbon had transitioned to biologically activated carbon, as determined based on soluble chemical oxygen demand removal, adsorption was still observed as the main mechanism for contaminants of emerging concern and nitrate removal. Vacuum ultraviolet pre-treatment markedly improved contaminants of emerging concern removal through the integrated system, achieving 40% at VUV-E1 and 90% at VUV-E10. When applied as post-treatment to zeolite column effluents, VUV-E1 and VUV-E10 further increased contaminants of emerging concern removal by 20% and 90%, respectively. In the zeolite system, vacuum ultraviolet pre-treatment also increased soluble chemical oxygen demand removal efficiency, indicating that higher energy vacuum ultraviolet increased biodegradability. Total prokaryotes were two-fold more abundant in biologically activated carbon than in zeolite, with vacuum ultraviolet pretreatment markedly affecting microbial diversity, both in terms of richness and composition. Media type only marginally affected microbial richness in the biofilters but showed a marked impact on structural composition. No clear relationship between compositional structure and depth was observed.

Insight into the Storage-Related Oxidative/Hydrolytic Degradation of Olive Oil Secoiridoids by Liquid Chromatography and High-Resolution Fourier Transform Mass Spectrometry.

The study of negative effects potentially exerted by the exposure to oxygen and/or light and, thus, also by the type of container on the quality of extra virgin olive oil (EVOO) during its prolonged storage requires an appropriate choice of analytical methods and components to be monitored. Here, reverse-phase liquid chromatography coupled to high-resolution/accuracy Fourier transform mass spectrometry with electrospray ionization was exploited to study oxidative/hydrolytic degradation processes occurring on the important bioactive components of EVOO known as secoiridoids, i.e., oleuropein and ligstroside aglycones, oleacin, and oleocanthal, during storage up to 6 months under controlled conditions. Specifically, isomeric oxidative byproducts resulting from the transformation of a carbonylic group of the original secoiridoids into a carboxylic group and compounds resulting from hydrolysis of the ester linkage of secoiridoids, i.e., elenolic and decarboxymethyl elenolic acids and tyrosol and 3-hydroxytyrosol, were monitored, along with their precursors. Data obtained from EVOO storage at room temperature in glass bottles with/without exposure to light and/or oxygen indicated that, although it was more relevant if a periodical exposure to oxygen was performed, a non-negligible oxidative degradation occurred on secoiridoids also when nitrogen was used to saturate the container headspace. In a parallel experiment, the effects of storage of the same EVOO (250 mL) for up to 6 months in containers manufactured with different materials/shapes were considered. In particular, a square dark glass bottle, a stainless-steel can, and a ceramic jar, typically used for EVOO commercialization, and a clear polyethylene terephthalate bottle, purposely chosen to prompt secoiridoid degradation through exposure to light and oxygen, were compared. Dark glass was found to provide the best combined protection of major secoiridoids from oxidative and hydrolytic degradation, yet the lowest levels of oxidized byproducts were observed when the stainless-steel can was used.