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In this study, photolytic and photocatalytic removal of the antibiotic sulfamethoxazole (SMX) under UVC radiation (λ=254 nm) was investigated. The light intensity distribution inside the batch photoreactor was characterized by azoxybenzene actinometry. The intensity of incident radiation was found to be a strong function of position inside the reactor. 12 mg L(-1) of SMX was completely removed within 10 min of irradiation under UVC photolysis, compared to 30 min under TiO(2) photocatalysis. COD measurement was used as an indication of the mineralization efficiency of both processes and higher COD removal with photocatalysis was shown. After 6h of reaction with photolysis and photocatalysis, 24% and 87% removal of COD was observed, respectively. Two of the intermediate photo-products were identified as sulfanilic acid and 3-amino-5-methylisoxazole by direct comparison of the HPLC chromatograms of standards to those of treated solutions. Ecotoxicity of treated and untreated solutions of SMX towards Daphnia magna was also investigated. It was found that a 3:1 ratio of sample to standard freshwater and a high initial concentration of 60 mg L(-1) of SMX were used to obtain reliable and reproducible results. The photo-products formed during photocatalytic and photolytic processes were shown to be generally more toxic than the parent compound.

High-throughput acute and chronic toxicity tests using Vibrio fischeri were used to assess the toxicity of a variety of fungicides, herbicides, and neonicotinoids. The use of time points beyond the traditional 30 min of an acute test highlighted the sensitivity and applicability of the chronic toxicity test and indicated that for some compounds toxicity is underestimated using only the acute test. The comparison of EC values obtained from acute and chronic tests provided insight regarding the toxicity mode of action, either being direct or indirect. Using a structure-activity relationship approach similar to the one used in hazard assessments, the relationship between toxicity and key physicochemical properties of pesticides was investigated and trends were identified. This study not only provides new information regarding acute toxicity of some pesticides but also is one of the first studies to investigate the chronic toxicity of pesticides using the test organism V. fischeri. The findings demonstrated that the initial bioluminescence has a large effect on the calculated effective concentrations for target compounds in both acute and chronic tests, providing a way to improve and standardize the test protocol. In addition, the findings emphasize the need for additional investigation regarding the relationship between a toxicant's physicochemical properties and mode of action in nontarget organisms.

Photolytic and photocatalytic removals of 17␣-ethinylestradiol (EE2) and levonorgestrel (LNG) in pharmaceutical wastewater were investigated under UVC radiation. Wastewater collected from WYETH, St-Laurent, Canada contained high concentrations of EE2 and LNG in suspension and coloring agent tartrazine in solution. Aqueous phase removals of EE2 and LNG were studied as individual contaminants in water and in complex matrices including: co-contaminants in water, in simulated synthetic wastewater and in the wastewater. After 30 min of UVC photocatalysis of the individual contaminants, removal efficiencies of EE2 and LNG were 92% and 97%, respectively, while higher photolytic removal was observed for LNG (94%) compared to EE2 (60%). Hydroxyl radicals were shown to contribute significantly to the removal of both compounds in water. In contrast to EE2, photolytic removal of LNG was higher than its photocatalytic removal efficiencies in all complex matrices. Higher photolytic removal of LNG was attributed to the fact that it absorbs UVC radiation considerably more than EE2. Lower photocatalytic removals of LNG in complex matrices compared to its photocatalytic removal as an individual contaminant was due to the presence of EE2 at concentrations up to five times larger than LNG in water, thus leading to increased competition for hydroxyl radicals and retarding LNG removal. In the wastewater matrix photocatalytic removals for EE2 and LNG were similar at 48%, whereas the photolytic removal of LNG (76%) was higher than EE2 (29%). The applicability of UVC processes for reduction of hormone content in similar wastewaters was demonstrated.

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Although conventional wastewater treatment technologies are effective at removing many contaminants of emerging concern (CECs) from municipal wastewater, some contaminants are not removed efficiently. Ozonation may be a treatment option for reducing the concentrations of recalcitrant CECs in wastewater, but this process may generate toxic transformation products. In the present study, we conducted semibatch experiments to ozonate municipal wastewater effluent spiked with 5 commonly detected CECs. The purpose of the present study was to evaluate whether ozonation increased or decreased biological responses indicative of sublethal toxicity in juvenile rainbow trout (Oncorhynchus mykiss) injected intraperitoneally (i.p.) with extracts prepared from ozonated and nonozonated wastewater effluent. Blood, liver, and brain tissues were collected from the fish at 72 h post injection for analysis of a battery of biomarkers. In fish i.p. injected with the extracts from nonozonated wastewater effluent, significant induction of plasma vitellogenin (VTG) was observed, but ozonation of the municipal wastewater effluent spiked with CECs significantly reduced this estrogenic response. However, in fish injected with extracts from spiked municipal wastewater effluent after ozonation, the balance of hepatic glutathione in its oxidized (glutathione disulfide [GSSG]) form was altered, indicating oxidative stress. Levels of the neurotransmitter serotonin were significantly elevated in brain tissue from trout injected with the extracts from ozonated spiked municipal wastewater effluent, a biological response that has not been previously reported in fish. Other in vivo biomarkers showed no significant changes across treatments. These results indicate that ozonation reduces the estrogenicity of wastewater, but may increase other sublethal responses. The increase in biomarker responses after ozonation may be because of the formation of biologically active products of transformation of CECs, but further work is needed to confirm this conclusion. Environ Toxicol Chem 2018;37:274-284. C 2017 SETAC