12-10: Field Evaluation and Verification of Biological Control in OperatingPulse Electric Field Devices (PEFDs) have been used as the sole source of water treatment in evaporative cooling water systems for over 10 years often with good results. Several field evaluations will be presented that provide detailed data on microbiological control entirely by the PEFDs. This paper will present both field and laboratory test data independently obtained from operating cooling tower water systems that rely solely on PEFDs for