Effect of spring runoff on 2,6-dichloro-1,4-benzoquinone formation during water treatment

This study investigated the impacts of spring runoff on the formation of halobenzoquinones (HBQs) and their correlation with common water quality parameters (WQPs) and aromatic amino acids (AAs) in source water. Source water and treated water samples were collected at two drinking water treatment plants in 2021, 2022, and 2023. HBQs and aromatic AAs were analyzed using solid phase extraction with high performance liquid chromatography-tandem mass spectrometry methods. The only HBQs detected in treated water were 2,6-dichloro-1,4-benzoquinone (DCBQ) and hydroxy‑DCBQ (OH-DCBQ). The concentration of DCBQ was 3-4 times higher during spring runoff events than during non-spring-runoff periods, suggesting the impact of spring runoff on the formation of DCBQ. The DCBQ concentrations in finished water positively correlated with the color, dissolved organic carbon, total organic nitrogen, and specific ultraviolet absorbance WQPs of source water in 2021 and 2022. The temporal trend of the total aromatic AAs determined in source water was strongly and positively correlated to DCBQ in finished water. Finally, there was a significant positive correlation between the concentration of DCBQ determined immediately following the addition of chlorine and the presence of its transformation product, OH-DCBQ, in finished water. The results also showed that powdered activated carbon can remove some of the HBQ precursors in the source water to reduce DCBQ formation. This study demonstrated that WQPs and aromatic AAs are useful indicators for the removal of precursors to reduce HBQ formation during drinking water treatment.