Digester supernatant contains high concentrations of nitrogen and phosphorus. Also, poor quality supernatant discharged from an anaerobic digester can have an adverse effect on the overall efficiency of a wastewater treatment plant. The report discusses the building and demonstrating of a unique, trailer-mounted, and completely self-contained pilot plant. The pilot plant is designed to investigate the improvement of digester supernatant quality, with particular emphasis on the removal of nitrogen and phosphorus. The pilot plant treatment sequence consists of carbon dioxide removal via air-stripping, lime precipitation of phosphorus and carbonaceous particulate matter, and removal of nitrogen by packed-tower ammonia-stripping. The pilot plant was operated over a two-month period at a trickling filter plant where two-stage anaerobic digestion is practiced. It was found that 80-95% of supernatant phosphorus could be removed at a lime dosage equal to 50 pounds of hydrated lime per pound of phosphorus removed. Average ammonia-nitrogen removal was 82%, achieved at an air flow rate equal to 83,000 cubic feet of air per pound of NH3-N removed. Normal lime precipitation removed about one-half of the supernatant TOC, COD, AND Organic Nitrogen. The average decrease in suspended solids was 64%. (Author)