The overall objectives of this project were to modify, demonstrate, and optimize an existing treatment process to simultaneously remove both arsenic and manganese. Installing a single process to simultaneously remove both arsenic and manganese is desirable to simplify operations, reduce costs, and minimize plant footprints. A secondary objective was to establish an efficient design approach for other utilities implementing this process. This project was conducted at a full-scale operating well site with an existing manganese removal system. This project provides practical results that are directly applicable to utilities that have both arsenic and manganese issues. The treatability and other operating information obtained by this full-scale study could serve as benchmarks for other utilities that are considering this simple technology. The bench- and pilot-testing protocols established in this project will allow utilities to set up their own bench and pilot tests and obtain the planning and design information they need with minimal effort. The findings on the arsenic concentrations in the backwash waste and the evaluation of various waste disposal options provide valuable insight for waste management, and the cost analysis presents a useful tool for project planning.