N-nitrosodimethylamine (NDMA) is a potent carcinogen that is frequently detected nitrosamine from water chloramination. This study investigated the occurrence of NDMA and its potential precursor, ranitidine (RNT), in four wastewater treatment plants (WWTPs). Additionally, the effects of chloramination methods and oxidative pretreatment on the NDMA formation potential (FP) were assessed. Concentration levels of NDMA in the WWTPs waters ranged from 2.5 (detection limit) to 72.6 ng/L, while RNT values ranged from 1.32 to 186.9 ng/L. Further study indicated that the NDMA-FPs from chloraminated wastewaters varied between 36.2 and 227.8 ng/L. Nonetheless, chloramination methods and oxidative pretreatment significantly impacted the NDMA-FP levels. For example, breakpoint chlorination and stepwise chloramination promoted NDMA-FP when compared to preformed chloramination, which could be attributed to the formation of dichloramine and chlorine species. In contrast, prechlorination was found to effectively mitigate NDMA-FP, based on integrated ultraviolet (UV) irradiation. Notably, UV irradiation with free chlorine (UV/Cl2) or permanganate (UV/MnO4 -) reduced NDMA-FP by up to 70%. This study suggests that UV/MnO4 - and UV/Cl2 may be used as alternative mitigation strategies for reducing nitrosamine-FP in the water treatment process.

Abstract
1. Introduction
2. Material and methods
    2.1 Chloramination of precursors and oxidative
    2.2 Analysis
3. Results and discussion
    3.1 NDMA occurrence and formation potential inwastewater
    3.2 Importance of chloramine methods
    3.3 NDMA formation potential reduction duringpretreatment
4. Conclusions
References

• 민기(한국과학기술연구원 물자원순환연구단) | Mingizem Gashaw Seid (Center for Water Cycle Research, Korea Institute of Science and Technology)
• 손아섬(한국과학기술연구원 물자원순환연구단, 고려대학교 건축사회환경공학과) | Aseom Son (Center for Water Cycle Research, Korea Institute of Science and Technology, Civil, Environmental, and Architectural Engineering, Korea University)
• 조강우(포항공과대학교 환경공학부,연세대학교 미래융합연구원) | Kangwoo Cho (Division of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Institute for Convergence Research and Education in Advanced Technology (I-CREATE), Yonsei University)
• 홍석원(한국과학기술연구원 물자원순환연구단,과학기술연합대학원대학교 한국과학기술연구원스쿨 에너지-환경 융합공학과) | Seok Won Hong (Center for Water Cycle Research, Korea Institute of Science and Technology,Division of Energy and Environment Technology, KIST-School, University of Science and Technology) Corresponding author