A facile and green pretreatment method for nonionic total organic halogen (NTOX) analysis in water – Step II. Using photolysis to convert NTOX completely into halides

et al. 2021

Wastewater ozonation forms various toxic byproducts, such as aldehydes, bromate, and organic bromine. However, there is currently no clear understanding of the overall toxicity changes in ozonated wastewater because pretreatment with solid phase extraction cannot retain inorganic bromate and volatile aldehydes, yet contributions of known ozonation byproducts to toxicity are unknown. Moreover, compared with bromate, organic bromine did not receive widespread attention. This study evaluated the toxicity of ozonated wastewater by taking aldehydes, bromate, and organic bromine into consideration. In the absence of bromide, formaldehyde contributed 96–97% cytotoxicity and 92–95% genotoxicity to HepG2 cells among the detected known byproducts, while acetaldehyde, propionaldehyde, and glyoxal had little toxicity. Both formaldehyde and dibromoacetonitrile drove toxicity among the known byproducts when bromide was present. Toxicity assays in HepG2 cells showed that when secondary effluents contained no bromide, the cytotoxicity of the nonvolatile organic fraction (NVOF) was reduced by 56–70%, and genotoxicity was completely removed after ozonation. However, the formed aldehydes (volatile organic fraction, VOF) led to increased overall toxicity. In the presence of bromide, compared with the secondary effluent, ozonation increased the cytotoxicity of the NVOFBr from 3.4–4.0 mg phenol/L to 10.3–13.9 mg phenol/L, possibly due to the formation of organic bromine. In addition, considering the toxicity of VOFBr (VOF in the presence of bromide, including aldehydes, tribromomethane, etc.), the overall cytotoxicity and genotoxicity became much higher than those of the secondary effluent. Although bromate had a limited impact on cytotoxicity and genotoxicity, it caused an increase in oxidative stress in HepG2 cells. Therefore, when taking full account of nonvolatile, volatile, and inorganic fractions, ozonation generally increases the toxicity of wastewater.

Section: Methodsmentioning

confidence: 99%

Toxicity of Ozonated Wastewater to HepG2 Cells: Taking Full Account of Nonvolatile, Volatile, and Inorganic Byproducts

et al. 2021

“…TOBr was determined using a previously reported method. 39 Briefly, the dried extracted organic byproducts were first dissolved in ultrapure water, then irradiated with a 185 nm and 12 W vacuum ultraviolet light for 1 h. Bromide obtained from the conversion of organic bromine was then measured by ion chromatography as described above. Trace bromide before ultraviolet irradiation, which might be attributed to retention on the SPE cartridge, was also measured.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

“…For total organic bromine (TOBr) measurement, to be consistent with the toxicity assay, organic byproducts formed during ozonation were extracted by SPE, eluted with organic solvents, and dried under a nitrogen stream using the same method as described above. TOBr was determined using a previously reported method . Briefly, the dried extracted organic byproducts were first dissolved in ultrapure water, then irradiated with a 185 nm and 12 W vacuum ultraviolet light for 1 h. Bromide obtained from the conversion of organic bromine was then measured by ion chromatography as described above.…”

Section: Methodsmentioning

confidence: 99%

Ammonia-Mediated Bromate Inhibition during Ozonation Promotes the Toxicity Due to Organic Byproduct Transformation

Zhang

et al. 2020

Ammonia (NH 4 + ) and hydrogen peroxide (H 2 O 2 ) have been widely used to inhibit bromate formation during ozonation. However, organic byproducts can also pose a risk under these conditions. During bromate inhibition, the influence of NH 4+ and H 2 O 2 on organic byproducts and their toxicity should be elucidated. Our study found that NH 4 + suppressed organic bromine, but might result in increased toxicity. Adding 0.5 mg/L of NH 4 + −N substantially increased both the formation of cytotoxicity and genotoxicity (DNA double-strand breaks) of organic byproducts from 0.6 to 1.6 mg-phenol/L, and from 0.3 to 0.8 μg-4-NQO/L (0.5 mg/L Br − , 5 mg/L O 3 ). NH 4 + decreased bromate, but increased the overall toxicity of the integrated byproducts (organic byproducts and bromate). Organic nitrogen measurements and 15 N isotope analysis showed enhanced incorporation of nitrogen into organic matter when NH 4 + and Br − coexisted during ozonation. NH 4 + decreased the formation of brominated acetonitriles, but enhanced the formation of brominated nitromethanes and brominated acetamides. These brominated nitrogenous byproducts were partially responsible for this increase in toxicity. Different from ammonia, H 2 O 2 could reduce both bromate and the toxicity of organic byproducts. In the presence of 0.5 mg/L Br − and 10 mg/L O 3 , adding H 2 O 2 (0.5 mM) substantially suppressed bromate, cytotoxicity formation and genotoxicity formation by 88%, 63% and 67%. This study highlights that focusing on bromate control with NH 4 + addition might result in higher toxicity. Efforts are needed to effectively control the toxicities of bromate and organic byproducts simultaneously.

“…Similarly, by combining the pairs of ion clusters in the UPLC/ESI-tqMS PIS spectra of m / z 35 and 37 (Figure j–r and Figure S5), many chlorine-containing DBPs (Cl-DBPs) were selectively detected in the sample, including ion clusters m / z 177/179/181/183, 197/199/201, 213/215/217/219, 225/227/229, 231/233/235/237, 259/261/263/265, 293/295/297/299, etc. The ion clusters m / z 215/217/219, 193/195, and 171/173/175 should correspond to the frequently observed DBPs dibromoacetic acid, 2-bromobutenedioic acid, and bromochloroacetic acid, respectively. ,− Other ion clusters should be new or less-reported emerging DBPs.…”

Section: Resultsmentioning

confidence: 99%

“…By summation of all the ion intensities within the m / z range of 100–500 in a PIS m / z 79 (or m / z 35) spectrum, the total ion intensity value TII PIS79 (or TII PIS35 ) of polar Br-DBPs (or Cl-DBPs) in a water sample can be obtained. Under fixed instrument setting, the value can be used to indicate the total amount of polar halogenated DBPs and comparatively evaluate the formation of those DBPs in different water samples. ,, To better compare the levels of the halogen-specific fractions, TII PIS35 data were normalized by multiplying by a coefficient and presented as TII PIS35N . For a commonly known polar DBP bromochloroacetic acid containing one bromine and one chlorine, the ratio of the ion intensity observed under the PIS m / z 79 scan to that observed under the PIS m / z 35 scan was ∼4.3.…”

Section: Resultsmentioning

confidence: 99%

Identification, Formation, and Predicted Toxicity of Halogenated DBPs Derived from Tannic Acid and Its Biodegradation Products

Zhu

et al. 2019

Self Cite

Humic substances are commonly known disinfection byproduct (DBP) precursors. Tannic acid is one precursor of humic substances in organic degradation, and it occurs ubiquitously in both source water and wastewater. In this study, the biological degradation process was simulated under laboratory conditions, and the characteristics of DBP formation generated from the chlorination of tannic acid samples with different biodegradation times were explored. Twenty-six emerging halogenated DBPs were identified, and the formation pathways of the tannic acid-derived DBPs were tentatively proposed. Moreover, results demonstrated that the profile of the chlorinated DBP formation was significantly different from its brominated counterpart during biodegradation, and a general increasing trend of the ratio of TOBr/TOX or TII PIS79 /(TII PIS79 +TII PIS35 ) as biodegradation time increasing was noticeable. The observed trend could be mainly ascribed to the reactive sites of tannic acid shifting from relatively fast to slow sites during biodegradation. In addition, the comparative toxicity of the detected DBPs derived from tannic acid was predicted by using two quantitative structure−activity relationship models established previously. On the basis of both the two toxicity metrics (involving developmental toxicity and growth inhibition potency), the predicted toxicity data indicated that the emerging DBP group trihalo-(di)hydroxycyclopentane-1,3-diones may possess extremely high toxic potencies.