The purpose of the Pilot Plant installed at the City of Trenton was to establish the efficacy of removing phosphorous from waste water using a biological system. The project was initiated on February 1, 1967 and continued through to May 31, 1969. The major activities of this project were, the design and fabrication of the two 10 gpm activated sludge process uinits; the determination of the operating parameters which result in phosphorous removal and the operation of continuous flow through system utilizing acid stripping modification of conventional activated sludge for phosphorous removal. (Author)