Formation of Halogenated Byproducts upon Water Treatment with Peracetic Acid.

Peracetic acid has quickly gained ground in water treatment over the last decade. Specifically, its disinfection efficacy toward a wide spectrum of microorganisms in wastewater is accompanied by the simplicity of its handling and use. Moreover, peracetic acid represents a promising option to achieve disinfection while reducing the concentration of typical chlorination byproducts in the final effluent. However, its chemical behavior is still amply debated. In this study, the reactivity of peracetic acid in the presence of halides, namely, chloride and bromide, was investigated in both synthetic waters and in a real contaminated water. While previous studies focused on the ability of this disinfectant to form halogenated byproducts in the presence of dissolved organic matter and halides, this work indicates that peracetic acid also contributes itself as a primary source in the formation of these potentially carcinogenic compounds. Specifically, this study suggests that 1.5 mM peracetic acid may form around 1-10 µg/L of bromoform when bromide is present. Bromoform formation reaches a maximum at near neutral pH, which is highly relevant for wastewater management.

Evaluation of Fenton and modified Fenton oxidation coupled with membrane distillation for produced water treatment: Benefits, challenges, and effluent toxicity.

Membrane distillation is a promising technology to desalinate hypersaline produced waters. However, the organic content can foul and wet the membrane, while some fractions may pass into the distillate and impair its quality. In this study, the applicability of the traditional Fenton process was investigated and preliminarily optimized as a pre-treatment of a synthetic hypersaline produced water for the following step of membrane distillation. The Fenton process was also compared to a modified Fenton system, whereby safe iron ligands, i.e., ethylenediamine-N,N'-disuccinate and citrate, were used to overcome practical limitations of the traditional reaction. The oxidation pre-treatments achieved up to 55% removal of the dissolved organic carbon and almost complete degradation of the low molecular weight toxic organic contaminants. The pre-treatment steps did not improve the productivity of the membrane distillation process, but they allowed for obtaining a final effluent with significantly higher quality in terms of organic content and reduced Vibrio fischeri inhibition, with half maximal effective concentration (EC50) values up to 25 times those measured for the raw produced water. The addition of iron ligands during the oxidation step simplified the process, but resulted in an effluent of slightly lower quality in terms of toxicity compared to the use of traditional Fenton.

Structural elucidation of bisphenol E and bisphenol S photoinduced by-products by high-resolution electrospray ionisation mass spectrometry and tandem mass spectrometry.

RATIONALE: Bisphenol E (BPE) and bisphenol S (BPS) have recently replaced bisphenol A as monomers for producing polycarbonates. However, BPE and BPS can pose hazards as they are known to be endocrine disruptors. Despite the huge increase in their use, there is a lack of data regarding the toxicity and effects of BPE and BPS. METHODS: We investigated the photoinduced transformation of BPE and BPS when subjected to sun-simulated radiation and using TiO2 as a photocatalyst. Analyses of BPE, BPS and their by-products were performed by high-performance liquid chromatography/high-resolution mass spectrometry (HPLC/HRMS) using an orbitrap mass analyzer in negative electrospray ionisation (ESI) mode. The chromatographic separations were achieved by employing a C18 reversed-phase column, and the transformation products (TPs) were elucidated structurally using HRMS and multistage MS experiments performed in collision-induced dissociation (CID) mode. RESULTS: The transformation of bisphenol S involved the formation of twelve by-products, while ten TPs were detected following BPE degradation. For bisphenol S, the cleavage of the molecule is a very important transformation route, together with the hydroxylation of the substrate to provide mono- and poly-hydroxylated TPs. For bisphenol E, the two main routes were hydroxylation and ring opening. Acute toxicity for BPS, BPE and their TPs was assessed using the Vibrio fischeri assay, highlighting that their initial transformation involved the formation of TPs that were more toxic than the parent compound. CONCLUSIONS: The HPLC/HRMS method developed was useful for characterising and identifying newly formed TPs from bisphenol E and bisphenol S. This study aimed to examine the structure of twenty by-products identified during TiO2 -mediated photolysis and to evaluate acute toxicity over time.

Study of the photoinduced transformations of sertraline in aqueous media.

In the present study, the photoinduced degradation of the antidepressant drug sertraline under artificial solar radiation was examined. Photolysis was studied under different experimental conditions to explore its photolytic fate in the aqueous environment. Photolytic degradation kinetics were carried out in ultrapure water, wastewater effluent, as well as in the presence of dissolved organic matter (humic acids), bicarbonate and nitrate ions which enabled their assessment on sertraline photo-transformation. The reaction of sertraline with photoactive compounds accelerated sertraline transformation in comparison with direct photolysis. Moreover, TiO2-mediated photocatalytic degradation of sertraline was investigated, and focus was placed on the identification of by-products. As expected, photocatalysis was extremely effective for sertraline degradation. Photocatalytic degradation proceeded through the formation of forty-four transformation products identified by HPLC-HRMS and after 240 min of irradiation total mineralization was achieved. Microtox bioassay (Vibrio fischeri) was employed to assess the ecotoxicity of the photocatalysis-treated solutions and results have indicated that sertraline photo-transformation proceeds through the formation of toxic compounds.