Water Flow Rates / UV Exposure
The amount of time that waterborne microorganisms are in direct contact with UV radiation produced by the lamp inside the exposure chamber is the UV exposure rate. Exposure rates have long been established for a variety of living microorganisms, including common bacteria (15,000 µWs/cm²) and single-cell waterborne algae (22,000 µWs/cm²). All UV sterilizers, regardless of brand or whether called a sterilizer or a clarifier, must sterilize the targeted microorganism in order to achieve success.

A UV sterilizer's water flow rate is calculated by recognizing the established UV exposure rate at 250-280 nm for a targeted microorganism, in this case waterborne algae which is 22,000 µWs/cm². The UV operating capacity is based on the UV Output performance of the UV lamp, lamp arc length and the positioning of the lamp inside the UV exposure chamber. The operating capacity of the sterilizer must be matched to the established UV exposure rate of the waterborne algae (water flow rate @ 22,000 µWs/cm²). Other performance factors include water temperature and UV radiation transmittance.

UV Radiation Transmittance in Water
Emperor Aquatics is the only UV manufacturer to consider UV radiation transmitted through dirty or “green” water when calculating UV flow rates. Ask yourself, "Why do many folks consider purchasing a UV for their pond?" They do it, to solve a green water problem. If the customer purchases a sterilizer and installs it while a waterborne algae bloom is present, the UV’s water flow rate must consider the affect that the algae bloom will have on the transmittance of UV radiation through the green water.

This explains why our recommended water flow rates are dramatically lower than all competing brands of UV sterilizers. Unlike most UV manufacturers, when calculating water flow rates Emperor Aquatics, Inc. applies a .45 absorption coefficient factor for water clarity along with a 20 percent transmittance reduction for the quartz sleeve into the EPA exposure rate formula. This compensates for loss of UV radiation traveling through the sleeve’s glass and turbid green water.

Our company’s extensive research, development and field experience prove that applying UV sterilization conservatively is the only acceptable approach to achieving successful results. Emperor Aquatics is the only manufacturer following the UV sterilization guidelines under chart 7-30 in the EPA Design Manual for Municipal Waste Water Disinfection.