Due to population growth and urbanization, water resources are increasingly affected by municipal wastewater effluents in urban water cycle. Municipal wastewater effluents contain various contaminants of concern such as antibiotics, antibiotic resistant bacteria and genes, nitrosamines or precursors of nitrosamines etc. Oxidation processes (e.g., ozonation, UV/H2O2 or ferrate oxidation) can be applied for enhanced wastewater treatment or drinking water treatment to minimize the negative effects of such contaminants to aquatic organisms or humans. Recent studies have also demonstrated that many micropollutants can be eliminated by ozonation at economically applicable treatment condition. With these backgrounds, I will talk about the following selected research topics in detail: 1) deactivation kinetics of antibiotics resistance genes during oxidative water treatment and 2) formation of NDMA from ozonation of hydrazide compounds: reaction kinetics, mechanisms, and implications for wastewater ozonation.