A Life Aquatic: Sensors Keep Aquarium Stable

The Shark Reef at Mandalay Bay Resort Casino exhibit contains over 1,200 aquatic species including sharks, crocodiles, piranhas, rays, sea turtles, jellyfish, and other freshwater and saltwater fish. Las Vegas’ only AZA Accredited Animal Care Facility, i.e., by the American Zoo and Aquarium Association, the attraction also houses five of the 12 known existing golden saltwater crocodiles, one of the most endangered species in the world. Maintaining the environment for these very special species is a great challenge for the life support crew. To insure the best water quality possible, the exhibit relies on several analytical measurements using a variety of Signet instruments from GF Piping Systems.

Over 1.6 million gallons of water is recycled hourly through the array of pipes and water treatment equipment. About 300,000 gallons are used for freshwater exhibits, while the rest is salt water made onsite by mixing salt imported from the Red Sea with trace elements found in natural seawater. The recycled and incoming water can be treated consistently, but only with use of reliable analytical equipment. Salinity, pH, ORP, flow, and temperature are the measured parameters and controlling them insures water quality. The pH of incoming city water to the exhibit is never consistent due to various drought conditions in the Southwest. The recycled water also contains microorganisms and fish waste and must be treated before it’s 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 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 wasn’t 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, maintained at 32-33 ppt, are monitored using a conductivity sensor with a salinity meter. The salinity measurement is made using a Signet Model 5900 ProPoint Salinity Monitor and a conductivity sensor. This measurement is used to help the exhibit simulate salinity of natural seawater, which is critical to maintaining fish health.

The freshwater exhibits must maintain a pH level of around 7, while the salt water exhibits are at about 8.2. This is measured using Signet pH sensors and instruments. The pH value of the make-up water sent to the freshwater and salt water generation units must be monitored and controlled before it enters the unit 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.”

Signet panel mount instruments for various measurements at the Shark Reef Exhibit at the Mandalay Bay Resort Hotel

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 ensure enough ozone has been injected. Later down the line, ORP is measured again to insure the ozone and its by-products, such as hypochlorous or hypobromous acid, has dissipated out of the water. Any ozone left in the line “is an extreme irritant to the sensitive gills of the fish” says Jewell. A maximum ORP level of 350 millivolts is required.

Temperature of the water is maintained at approximate shoreline temperatures of 72° to 75°F. Still, 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’ fresh and salt water systems. Any upsets in the system can potentially cost the attraction millions of dollars to recover.

GF Piping, of Tustin, CA, supplies plastic pipe, fittings, tubing, valves, actuators, rotameters, fusion machines, secondary containment, tank linings, heat exchangers, custom products, and sensors and instrumentation for industrial process control. Contact: George Fischer Inc., 800-854-4090 or www.us.piping.georgefischer.com