Many regions in the United States have excessive levels of ammonia in their groundwater as a result of natural or agricultural sources. Although ammonia in water does not pose a direct health concern, nitrification (i.e., conversion of ammonia to nitrite and nitrate by bacteria) of significant levels of excessive ammonia from the source water in the drinking water distribution system may pose a concern. Specifically, nitrification in the distribution system leads to potential corrosion problems, oxidant demand, taste and odor complaints, and elevated nitrite levels. In addition, ammonia can interfere with the effectiveness of some drinking water treatment processes. Across the United States, including small communities like Palo, Iowa, (approx. pop. 1026) there are relatively high levels of ammonia in the drinking water supplies. PaloÃ¢â‚¬â„¢s groundwater contains 3.3 mg N/L. Given the negative issues associated with ammonia, there was a serious need for Palo to establish an effective treatment approach to remove it from their water. With the support of the United States Environmental Protection Agency (EPA) Region 7, the Iowa Department of Natural Resources (DNR) and the City of Palo, EPA researchers performed a year-long pilot study in Palo to evaluate the use of an innovative biological drinking water treatment process to remove ammonia from their water. After the success of the pilot study, the DNR approved the cityÃ¢â‚¬â„¢s plans to construct a full-scale treatment system based on the design and operating configurations identified during the pilot study. The objective of this study was to document the operation and treatment effectiveness of the city of PaloÃ¢â‚¬â„¢s innovative full-scale biological ammonia removal drinking water treatment plant. The treatment plant engineering design criteria and operating conditions are presented, and development of the project from pilot to full-scale is discussed. Lastly, lessons learned from the project, and future considerations when designing and operating biological treatment systems for ammonia reduction are presented.