Landfill leachate and municipal wastewater are major sources of chemical pollutants that contaminate our drinking water sources. Evaluating the dissolved organic chemical composition in wastewater treatment plants is therefore essential to understand how the discharge impacts the environment, wildlife, and human health. In this study, we utilized a nontargeted analysis method coupling liquid chromatography and tandem mass spectrometry (LC-MS/MS) to analyze chemical features at different points along two landfill leachate treatment plants (LLTPs) and two municipal wastewater treatment plants (WWTPs) in the Southeastern United States. Significant feature differences were observed for the WWTPs where activated sludge clarification was employed versus the LLTPs utilizing reverse osmosis. Specifically, even though both LLTPs had the largest number of features in their influent water, their effluent following reverse osmosis yielded a lower number of features than the WWTPs. Additionally, the clarification processes of each WWTP exhibited different efficiencies as chemical disinfection removed more features than UV disinfection. Feature identification was then made using the LC, MS, and MS/MS information. Analysis of the identified molecules showed that lipids were the most effectively removed from all plants, while alkaloid and organic nitrogen compounds were the most recalcitrant.