Bromide induced the formation of brominated halonitromethanes from aspartic acid in the UV/chlorine disinfection process

Brominated halonitromethanes (Br-HNMs) are generated in water disinfection processes and present high toxicity to human health. This work used aspartic acid (ASP) as the precursor to reveal that bromide (Br⁻) induced the production of Br-HNMs in the UV/chlorine disinfection process. Consequently, six Br-HNMs were identified, and their yields presented an increasing and then declining evolution over the reaction time from 0 to 15 min. Also, the total Br-HNMs yield reached the maximum of 251.1 μg L⁻¹ at 5 min and then declined to 107.1 μg L⁻¹. The total Br-HNMs yield increased from 2.40 to 251.14 μg L⁻¹ with the increase of Cl₂:Br⁻ ratios from 0.25 to 3.0 by increasing free chlorine dosage with a fixed Br⁻ concentration, and it increased from 207.59 to 251.14 μg L⁻¹ and then decreased to 93.44 μg L⁻¹ with the increase of Cl₂:Br⁻ ratio from 1.0 to 3.6 by increasing Br⁻ concentration with a fixed free chlorine dosage. Besides, the total Br-HNMs yield reached the highest value (251.14 μg L⁻¹) at pH 7.0 and the lowest value (74.20 μg L⁻¹) at pH 8.0. Subsequently, the possible reaction mechanism of Br-HNMs generated from ASP was deduced, and the changes in toxicity of Br-HNMs also followed an increasing and then declining trend, closely relating to Br-HNMs yields and Br⁻ utilization. This work explored and illustrated the yields, influence factors, reaction mechanisms, and toxicity of Br-HNMs formed from Br⁻ containing ASP water during UV/chlorine disinfection, which might help to control Br-HNMs formation.