The Shark Reef attraction, at the Mandalay Bay Resort Hotel in Las Vegas’ only American Zoo and Aquarium Association Accredited Animal Care Facility, contains more than 1,200 aquatic species including sharks, crocodiles, piranhas, rays, sea turtles, jelly fish, and other freshwater and saltwater fish. The aquarium also houses five of the 12 known existing golden saltwater crocodiles, one of the most endangered species in the world. Maintaining the water environment for these very special species is a great challenge for the life support crew. To ensure the best water quality possible, the exhibit relies on several analytical measurements using a variety of Signet instruments provided by GF Piping Systems (Tustin, Calif.).
More than 1.6 million gal of water is recycled hourly through the vast array of pipes and water treatment equipment. Approximately 0.3 million gal are used for the freshwater exhibits while the rest of the water, 1.3 million gal, is saltwater. The saltwater is made on site by mixing salt imported from the Red Sea, which contains trace elements found in natural seawater. In addition, approximately 4,000 gal of freshwater is delivered to the exhibit daily.
The recycled and incoming water can be treated consistently, but only with the use of reliable analytical equipment. Salinity, pH, ORP, flow and temperature are the measured parameters, and controlling them insures water quality. The pH of the incoming city water to the exhibit is never consistent due to the various drought conditions and elements that the water will carry. The recycled water also contains microorganisms and fish waste and must be treated before it is sent back into the exhibits.
Throughout the exhibits’ water treatment systems, flow measurements are made using Signet paddlewheel sensors at many measuring points to insure that the correct amount of water flows in and out of the displays. Initially, the flow sensors were installed in pipes with shorter-than-required straight runs upstream of the sensor. This was because there was not a lot of space to put longer run pipes. The life support operators have learned how to use their flow reading by looking at the consistent and repeatable flow reading.
Salinity levels of the salt water are monitored using a conductivity sensor with a salinity meter. The salinity is maintained at 32 to 33 parts per thousand. The salinity measurement is made using the Signet Model 5900 ProPoint Salinity Monitor and a conductivity sensor. This measurement is used to help the exhibit simulate the salinity of natural seawater, which is critical to maintaining fish health.
The freshwater exhibits must maintain a pH level of around 7 pH while the saltwater exhibits are at approximately 8.2 pH. The pH of the water is measured using Signet pH sensors and instruments. The pH value of the make-up water that is sent to the freshwater and saltwater generation units must be monitored and controlled before it enters the unit in order to control the amount of added treatment chemicals.
According to Jack Jewell, general curator at the Shark Reef at Mandalay Bay, “Low or declining pH and alkalinity levels can result in HCO3 imbalance in the animals on a long term basis.”
When the water is recycled from the fresh and salt water exhibits, ozone is injected for disinfection purposes. Using a Signet ORP sensor and instrument, the ORP of the water is measured to insure enough ozone has been injected. Later down the line, ORP is measured again to ensure that the ozone and its byproducts, such as hypochlorous or hypobromous acid, have dissipated out of the water. Any ozone left in the line “is an extreme irritant to the sensitive gills of the fish,” Jewell said. A maximum ORP level of 350 millivolts is required.
Temperature of the water is maintained at approximate shoreline temperatures of 72 to 75°F. However, the temperatures may vary slightly to simulate seasonal changes that are commonly found in nature. The water environment in the system must be maintained within tight parameters; anything outside of these parameters will be detrimental to the life of the sharks, golden saltwater crocodile and other aquatic life in the exhibits’ freshwater and saltwater systems. Any upsets in the system can potentially cost the attraction millions of dollars to recover.