Planning, design and construction of a water treatment plant to disinfect dry-weather flows discharging into the San Antonio River from the San Antonio Zoo. The San Antonio Zoo discharges about 1,700 gallons per minute, or about 2.5 million gallons per day of water to the San Antonio River during dry weather. The discharge contains high levels of bacteria, which contribute to water quality degradation in the river. The ultraviolet disinfection process is housed in a water treatment plant adjacent to the zoo outfall. The peak plant capacity is 3.88 MGD (for “dry-weather” flows), with storm water being bypassed around the plant. Environmental clearances and regulatory permits were required.