Deniz Nasuhoglu

Photo-removal of sulfamethoxazole (SMX) by photolytic and photocatalytic processes in a batch reactor under UV-C radiation (λmax=254 nm).

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.

Ozone treatment prevents the toxicity of an environmental mixture of estrogens on rat fetal testicular development.

Effluents from wastewater treatment plants contain a mixture of estrogens (MIX: 17β-estradiol: E2, estrone: E1, estriol: E3 and 17α-ethinylestradiol EE2). High doses of estrogens have been shown to negatively impact fetal testicular development, but the impact of low doses of estrogens in mixture have yet to be elucidated. Using an organ culture system in which embryonic 15.5 day-old rat testes were grown ex vivo, we showed that exposure to the MIX at environmentally relevant concentrations reduces testis growth. No effect was observed on testosterone secretion, but we quantified a significant decrease in the number of Sertoli cells and gonocytes because of higher rates of apoptosis. As ozone (O3) can be used as a disinfectant during wastewater treatment, we confirmed by HPLC-MS analysis that it removes the four parent compounds. Interestingly, the negative effects of the MIX were not observed when testes were exposed to the MIX treated with O3.

Evaluation of wastewater treatment by ozonation for reducing the toxicity of contaminants of emerging concern to rainbow trout (Oncorhynchus mykiss)

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.

Toxicity of extracts from municipal wastewater to early life stages of Japanese medaka (Oryzias latipes) to evaluate removals of micropollutants by wastewater treatment

Treatment of municipal wastewater reduces the concentrations of some pharmaceuticals and personal care products (PPCPs), hormones, and drugs of abuse. However, reduced concentrations of these micropollutants in wastewater may not correlate with reduced toxicity because transformations of micropollutants and/or the formation of disinfection by-products may generate toxic compounds. In the present study, we prepared extracts by solid phase extraction of samples collected from wastewater treatment plants (WWTPs) at various stages of treatment and tested these extracts for toxicity to early life stages of Japanese medaka (Oryzias latipes). Toxicity data for extracts prepared from a WWTP with secondary treatment showed that the numbers of exposed embryos (n = 12 per treatment) that did not hatch increased from 1 of 12 for the treatment with untreated effluent to 5 of 12 for the treatment with final treated effluent. For extracts prepared from a WWTP with tertiary treatment, toxicity among exposed embryos (n = 12 per treatment) also increased with each step of wastewater treatment, as shown by mortalities of 2 of 12 and 8 of 12 in treatments with extracts from untreated and final treated effluent, respectively, as well as an increase in the numbers of embryos that did not hatch from 2 of 12 to 9 of 12 in treatments with untreated and final treated effluent, respectively. Ozonation of treated wastewater collected from a third WWTP caused a high incidence of delayed hatch in exposed embryos (n = 24 per treatment). However, hatching success and the numbers of developmental abnormalities in embryos from this ozonation treatment were not different from controls. The present study shows the value of including toxicity testing to assess the effectiveness of technologies for treatment of municipal wastewater. Environ Toxicol Chem 2018;37:136-144.