Induced Genotoxicity in Nitrate‐Rich Water Treated With Medium‐Pressure Ultraviolet Processes

Abstract

Just as with chlorination, medium‐pressure (MP) ultraviolet (UV) treatment applied for disinfection purposes has been found to cause formation of genotoxic compounds, measured by the Ames test. By lowering the nitrate and dissolved organic carbon (DOC) content, the Ames test response was reduced substantially. The impact of nitrate photolysis on formation of genotoxic compounds was confirmed. A representative organic micro pollutant selection had no significant impact on the Ames test response. Formation of genotoxic compounds was found after MP UV disinfection, photolysis, and advanced oxidation of pretreated groundwater. In addition to nitrate and DOC content, aromaticity of organic matter had a strong impact. Ames test responses were converted into 4‐nitroquinoline oxide (4‐NQO) equivalent concentrations to enable quantitative comparison and to apply simple risk assessment. Based on the threshold for toxicological concern, already at doses applied for MP UV disinfection, the 4‐NQO equivalent concentration of formed genotoxic compounds in nitrate‐rich water exceeded the limit of no risk.

Organic Contaminant Abatement in Reclaimed Water by UV/H2O2 and a Combined Process Consisting of O3/H2O2 Followed by UV/H2O2: Prediction of Abatement Efficiency, Energy Consumption, and Byproduct Formation

“…The combination of UV with hydrogen peroxide (UV/H 2 O 2 ) is an advanced oxidation process (AOP) which has been shown to be a potential option to attenuate micropollutants in wastewater effluents. − Formation of toxic byproducts is typically less of an issue for UV/H 2 O 2 , , although formation of mutagenic/genotoxic byproducts was recently reported after medium pressure UV/H 2 O 2 treatment of nitrate-containing waters. , Studies in clean water matrices (e.g., drinking water) have shown that UV/H 2 O 2 is energy-intensive due to the low UV absorption of H 2 O 2 , which results in low OH radical (·OH) formation efficacy. This is compounded by the high ·OH scavenging rate by wastewater matrix components such as dissolved organic matter (DOM) , and by the limited UV transmittance of conventionally treated wastewaters.…”

Emerging investigator series: contributions of reactive nitrogen species to transformations of organic compounds in water: a critical review

“…Several nitroaromatic compounds and nitrosamines are known to produce a response in the Ames test, 25,30,100 and multiple studies have shown that RNS reactions with DOM during UV irradiation result in the formation of nitrophenols and a simultaneous increase in the Ames response. 51,78,94,95,101 Similarly, genotoxicity increased and nitrated products formed in a full-scale MPUV/H 2 O 2 treatment process. 78 The contribution of specific nitr(os)ated products to the increased genotoxicity is unknown.…”

Mitigation options for chemicals of emerging concern in surface waters; operationalising solutions-focused risk assessment

“…Oxidative processes are well-known for their possible creation of disinfection by-products, their formation also depends on process conditions and matrix properties such as nitrate and DOC content. [93][94][95]…”