Zeta Potential Measurements in the Control of Coagulation Chemical Doses

The Philadelphia Water Department, through its water quality and research division and its operations divisions, conducts studies to develop better methods of control of chemical doses, and greater efficiency in the use of chemicals. In previous laboratory, pilot plant, and full‐plant scale tests on coagulation, the laboratory jar stirring test has been used as a control method, and research has been directed to the effectiveness of various coagulants‐alum, ferrous and ferric salts, and sodium aluminate and of numerous coagulant aids. In this continuing work, the use of a zeta potential (ZP) microscope and cell was investigated. Some of the preliminary study results obtained with this equipment are presented, along with a brief discussion of the published findings of other writers and of the purpose and possible future use of ZP.