Comparison of UV and UV/chlorine system on degradation of 2,4-diaminobutyric acid and formation of disinfection byproducts in subsequent chlorination

Abstract

• UV/chlorine system showed extremely excellent performance in degrading DAB. • C-C bond and C-N bond fracture were the main reactions of DAB degradation by UV. • RCS produced by UV/chlorine system preferentially attacked amino groups on DAB. • N-DBPs had great formation potential when UV/chlorine was used as pretreatment. • THMs were more prone to bromine substitution than HANs. 2,4-diaminobutyric acid (DAB) is a common non-protein amino acid with extremely high neurotoxicity in water environment, posing a serious threat to human health and animal welfare around the world. Therefore, it is necessary to take appropriate measures to remove it. In this paper, degradation of DAB in UV and UV/chlorine system were studied, and transformation pathways of DAB were preliminarily proposed based on the identified transformation products. Moreover, formation of disinfection byproducts (DBPs) during post-chlorination under different conditions were also discussed. The results indicated that the presence of reactive substances in UV/chlorine system significantly promoted the degradation of DAB, but more DBPs and their precursors were produced at the same time. UV irradiation time, pH and Cl 2 /N affected the formation of DBPs during post-chlorination to various degrees. Notably, precursors of carbonaceous DBPs were mainly formed during UV irradiation, while those of nitrogenous DBPs were mainly formed during UV/chlorine system. In the presence of bromide, brominated DBPs were the absolute dominant species, while formation of chlorinated DBPs were inhibited. Furthermore, total trihalomethane and total haloacetonitrile increased with increasing bromide concentration. Overall, special attention should be paid to DBP formation when selecting UV or UV/chlorine system as pretreatment to eliminate DAB.