Effect of nitrite on the formation of halonitromethanes during chlorination of organic matter from different origin

This study examined the effects of sunlight irradiation on the trichloronitromethane formation potential (TCNM-FP) of wastewater effluents and the roles of nitrite and nitrate in this process. Using disinfected secondary effluents from four treatment plants, we observed that sunlight irradiation (320 W/m2) for 8 h attenuated the TCNM-FP by 17–47% for 9 of 14 samples but increased the TCNM-FP for two of the other samples. A longer irradiation time (≤36 h) further reduced the TCNM-FP in a non-nitrified effluent with low nitrite and nitrate concentrations but increased the TCNM-FP in two nitrified effluents by 2–3-fold. When nitrite (0.1–2 mg N/L) was spiked into effluent samples, an increase in the TCNM-FP after irradiation was observed. The higher the nitrite concentration, the greater the increase in the TCNM-FP. In the presence of ∼1 mg N/L of nitrite, sunlight irradiation for 8 h increased the TCNM-FP of four wastewater samples by 0.3–3.6 μg/mg C. In contrast, the spike of nitrate up to 20 mg N/L had no effect. The nitrite–sunlight effect was also observed for four model precursors (humic acid, tryptophan, tyrosine, and phenol). Humic acid and tryptophan featured larger increases in the TCNM-FP compared to those of tyrosine and phenol after sunlight irradiation.

Section: Environmental Implicationmentioning

confidence: 64%

Section: Resultsmentioning

confidence: 93%

Effects of Sunlight on the Trichloronitromethane Formation Potential of Wastewater Effluents: Dependence on Nitrite Concentration

Kralles

Dai

2019

“…The origin of nitromethane was investigated. Previous research observed a 10-fold increase in halonitromethane formation from chlorinating humic acid or natural organic matter (NOM) in the presence of nitrite, , and nitrite can increase chloropicrin formation from glycine during ozone/chlorine treatment . Therefore, prior to model precursor experiments, we investigated whether the nitrogen source of nitromethane in wastewater is dissolved organic nitrogen (DON) rather than inorganic nitrogen.…”

Section: Resultsmentioning

confidence: 99%

Transformation of N-Methylamine Drugs during Wastewater Ozonation: Formation of Nitromethane, an Efficient Precursor to Halonitromethanes

Shi

McCurry

2020

Potable reuse of wastewater is expanding, and ozonation for water reuse is becoming more common, either as a preoxidant before membranes or as part of ozone/biological activated carbon (O3/BAC) systems. However, previous research has demonstrated that ozone drastically increases the formation potential of genotoxic halonitromethanes (HNMs), including during O3/BAC. Chloropicrin, the most common HNM, is synthesized by chlorinating nitromethane, suggesting that nitromethane may be the immediate precursor of chloropicrin, although nitromethane is unlikely to occur naturally in wastewater. We hypothesized that wastewater ozonation forms nitromethane, which would be the key intermediate toward HNMs. Ozonation of wastewater effluent was shown to form abundant nitromethane, which explained the majority (in one case, all) of subsequent chloropicrin formation. Next, we investigated a suspected category of nitromethane precursor: stimulant drugs, such as ephedrine and methamphetamine, and certain antidepressants. These drugs all feature N-methylamine functional groups, and certain N-alkylamines have been shown to produce primary nitroalkanes upon ozonation. Ozonation of N-methylamine drugs ubiquitously formed nitromethane, typically at >50% yield. Subsequent chlorination converted nitromethane to chloropicrin. The reaction mechanism was investigated to understand the variation in nitromethane yield between different precursors. These results suggest that nitromethane fate during reuse and nitromethane control should be investigated.

“…The nitrite concentration in groundwaters varies from a few nanograms per liter to the milligram per liter level, depending on the microbial nitrification and denitrification activities . The bimolecular rate constant of NO 2 – oxidation by SO 4 •– is 8.8 × 10 8 M –1 s –1 .…”

Section: Introductionmentioning

confidence: 99%

Formation of Nitrophenolic Byproducts during Heat-Activated Peroxydisulfate Oxidation in the Presence of Natural Organic Matter and Nitrite

Yang

et al. 2019

Sulfate radical (SO4 •–)-based advanced oxidation is a viable in situ remediation technology for degrading organic contaminants in the subsurface. In this study, we demonstrated that SO4 •– could induce the activation of nitrite, an anion commonly present in the subsurface environment, leading to the formation of nitrophenolic byproducts. Fourier-transform infrared spectroscope and 15N nuclear magnetic resonance analysis revealed that the inorganic nitrite was incorporated into natural organic matter (NOM) to form organic nitrogen upon SO4 •– oxidation. Nitrophenolic byproducts, including 2-hydroxy-5-nitrobenzoic acid, 4-nitrophenol, and 2,4-dinitrophenol, were identified using high-resolution mass spectrometry in combination with a 15N labeling technique. Formation of nitrated byproducts was ascribed to the scavenging of SO4 •– by nitrite, which not only generated the nitrating agent NO2 • but also inhibited the degradation of organic compounds, making them more available to the reactions with NO2 •. The phenolic moieties in NOM served as the main reactive sites for NO2 • attack. The nitration begins with H abstraction on the phenoxy oxygen, followed by the addition of another NO2 • to its ortho or para site. Decarboxylation followed by NO2 • addition can also generate nitrophenolic byproducts. To the best of our knowledge, this is the first study reporting the nitration of NOM and formation of toxic nitrophenolic byproducts during SO4 •–-based oxidation. It sheds light on the potential risks of this technology in subsurface remediation practices.