To prevent legionella disease, hospitals are having to scald their lines periodically to stop the spread of respiratory disease throughout the building. If the controls are set to 90F in the first tank the water enters and then 120F in the second, the temperatures are just right to grow the legionella.
If however, the temperatures are set to 150F in the first one the water enters, the organisms are scalded to death. Then, the sanitized water can enter the last tank set at 120F, providing only dead organisms to be temporarily stored in the final tank. The second tank would need only to heat when the tank lost heat through the day.
If the first tank is set at 130F and the second at 150F, that would also sanitize the water. In most instances you would need a quality mixing valve to reduce the water temperature to prevent scalding children; they have been damaged by 110F water. The choice is yours.