Search

Graphical abstract Highlights • The influence of water matrix on the efficiency of AOTs is overviewed. • Photolysis, photocatalysis, UV/H 2 O 2 -, Fenton-, and O 3 -based processes are reviewed. • Dissolved organic matter and inorganics can act as inhibitors and/or promoters. • The effect results from the interplay of the co-existing substances. • The knowledge on the role of matrix constituents is crucial for installation of AOTs. Abstract Micropollutants (MPs) in the aquatic compartments are originated from many sources and particularly from the effluents of urban wastewater treatment plants (UWWTPs). Advanced oxidation technologies (AOTs) usually applied after biological processes, have recently emerged as effective tertiary treatments for the removal of MPs, but the oxidation rates of the single compounds may be largely affected by the constituent species of the water matrix. These species include dissolved organic matter and inorganic species (e.g., carbonate, bicarbonate, nitrite, sulphate, chloride). This review analyses the impact of such substances on common AOTs including photolysis, UV/H 2 O 2 , Fenton, photocatalysis, and ozone-based processes. The degradation efficiency of single MPs by AOTs results from the combined impact of the water matrix constituents, which can have neutral, inhibiting or promoting effect, depending on the process and the mechanism by which these water components react. Organic species can be either inhibitors (by light attenuation; scavenging effects; or adsorption to catalyst) or promoters (by originating reactive oxygen species (ROS) which enhance indirect photolysis; or by regenerating the catalyst). Inorganic species can also be either inhibitors (by scavenging effects; formation of radicals less active than hydroxyl radicals; iron complexation; adsorption to catalyst or decrease of its effective surface area) or promoters (e.g., nitrate ions by formation of ROS; iron ions as additional source of catalyst). The available data reviewed here is limited and the role and mechanisms of individual water components are still not completely understood. Further studies are needed to elucidate the wide spectrum of reactions occurring in complex wastewaters and to increase the adoption of AOTs in UWWTPs. [ABSTRACT FROM AUTHOR]

Although there are no legal discharge limits for micropollutants into the environment, some regulations have been published in the last few years. Recently, a watch list of substances for European Union-wide monitoring was reported in the Decision 2015/495/EU of 20 March 2015. Besides the substances previously recommended to be included by the Directive 39/2013/EU, namely two pharmaceuticals (diclofenac and the synthetic hormone 17-alpha-ethinylestradiol (EE2)) and a natural hormone (17-beta-estradiol (E2)), the first watch list of 10 substances/groups of substances also refers three macrolide antibiotics (azithromycin, clarithromycin and erythromycin), other natural hormone (estrone (E1)), some pesticides (methiocarb, oxadiazon, imidacloprid, thiacloprid, thiamethoxam, clothianidin, acetamiprid and triallate), a UV filter (2-ethylhexyl-4-methoxycinnamate) and an antioxidant (2,6-di-tert-butyl-4-methylphenol) commonly used as food additive. Since little is known about the removal of most of the substances included in the Decision 2015/495/EU, particularly regarding realistic concentrations in aqueous environmental samples, this review aims to: (i) overview the European policy in the water field; (ii) briefly describe the most commonly used conventional and advanced treatment processes to remove micropollutants; (iii) summarize the relevant data published in the last decade, regarding occurrence and removal in aqueous matrices of the 10 substances/groups of substances that were recently included in the first watch list for European Union monitoring (Decision 2015/495/EU); and (iv) highlight the lack of reports concerning some substances of the watch list, the study of un-spiked aquatic matrices and the assessment of transformation by-products. [ABSTRACT FROM AUTHOR]

The degradation of two organic pollutants (amoxicillin and diclofenac) in 0.1 mM aqueous solutions was studied by using advanced oxidation processes, namely ozonation, photolysis, photolytic ozonation, photocatalysis and photocatalytic ozonation. Diclofenac was degraded quickly under direct photolysis by artificial light (medium-pressure vapor arc, λ exc > 300 nm), while amoxicillin remained very stable. In the presence of ozone, regardless of the type of process, complete degradation of both organic pollutants was observed in less than 20 min. Photolysis or ozonation on their own led to modest values of total organic carbon (TOC) removal (<6% or 41%, respectively in 180 min), while for photocatalysis (no ozone present) a significant fraction of nonoxidizable compounds remained in the treated water (∼15% after 180 min). In the case of photolytic ozonation, the kinetics of TOC removal was slow. In contrast, a relatively fast and complete mineralization of amoxicillin and diclofenac (30 and 120 min, respectively) was achieved when applying the photocatalytic ozonation process. The absence of toxicity of the treated waters was confirmed by growth inhibition assays using two different microorganisms, Escherichia coli and Staphylococcus aureus . Photocatalytic ozonation was also applied to an urban wastewater spiked with both amoxicillin and diclofenac. The parent pollutants were easily oxidized, but the TOC removal was only as much as 68%, mainly due to the persistent presence of oxamic acid in the treated sample. The same treatment allowed the effective degradation of a wide group of micropollutants (pesticides, pharmaceuticals, hormones and an industrial compound) detected in non-spiked urban wastewater. [ABSTRACT FROM AUTHOR]

Abstract Urban wastewater treatment plants (WWTPs) are among the main anthropogenic sources for the release of contaminants of emerging concern (CECs) into the environment, which can result in toxic and adverse effects on aquatic organisms and consequently on humans. Unfortunately, WWTPs are not designed to remove CECs and secondary (e.g., conventional activated sludge process, CAS) and tertiary (such as filtration and disinfection) treatments are not effective in the removal of most CECs entering WWTP. Accordingly, several advanced treatment methods have been investigated for the removal of CECs from wastewater, including consolidated (namely, activated carbon (AC) adsorption, ozonation and membranes) and new (such as advanced oxidation processes (AOPs)) processes/technologies. This review paper gathers the efforts of a group of international experts, members of the NEREUS COST Action ES1403 who for three years have been constructively discussing the state of the art and the best available technologies for the advanced treatment of urban wastewater. In particular, this work critically reviews the papers available in scientific literature on consolidated (ozonation, AC and membranes) and new advanced treatment methods (mainly AOPs) to analyse: (i) their efficiency in the removal of CECs from wastewater, (ii) advantages and drawbacks, (iii) possible obstacles to the application of AOPs, (iv) technological limitations and mid to long-term perspectives for the application of heterogeneous processes, and (v) a technical and economic comparison among the different processes/technologies. Graphical abstract Unlabelled Image Highlights • Adsorption, O 3 , NF and RO membranes filtration can effectively remove CECs. • (Solar driven) AOPs appear competitive for CECs removal from urban wastewater. • When applying O 3 or AOPs ecotoxicological studies should be performed. • Lack of comparative investigations between consolidated and new processes • Conclusive evaluation of the most suitable and cost effective solution/s not yet possible [ABSTRACT FROM AUTHOR]