This project evaluated the performance of biological denitrification (BDN) for drinking water treatment with a specific focus on co-contaminant removal and minimizing waste stream volume. In addition to generating a knowledge base of the presence of denitrifying bacteria in different groundwater sources, the initial bench scale testing defined and validated a simple testing protocol that utilities may be able to implement in order to quickly determine whether denitrifying bacteria are present in their water sources. Evaluating co-contaminant removal with the BDN process is of great interest to water agencies having groundwater with multiple contaminants. Lastly, minimizing the waste treatment volume can drastically increase the maximum treatment capacity of utilities using this method. Tailored collaboration partner: Los Angeles County Department of Public Works. Published in 2014.