Phosphate removal by sorption on activated sludge was investigated in pilot and plant scale at the Baltimore, Maryland, Back River Sewage Works. These studies revealed that the activated sludge plant was obtaining high phosphorus removal under conditions similar to those found in the San Antonio Rilling Plant. Pilot investigations were made on the amenability of the waste and activated sludge to phosphate removal. The effects of suspended solids and dissolved oxygen concentrations in the mixed liquor, phosphate additions, oxygen demanding substrate additions, and the addition of aluminum, iron, and magnesium salts on phosphate removal were determined and found to agree with previous information. The waste and sludge were very amenable to phosphate removal. (Author)