Something’s fishy at the water treatment plant

By Nancy Bartels, Managing Editor

The new Georgia Aquarium (GA) in Atlanta is the largest indoor marine environment in the world. Opened in 2005, GA is home to more than 100,000 marine creatures, including beluga whales, whale sharks, piranhas, domestic catfish and even home-grown coral reefs. The centerpiece of the aquarium is the 6.2-million-gallon Ocean Voyager exhibit that replicates the marine life of Central America’s Meso-American Barrier Reef. This tank alone is 263 long x 126 wide x 33 ft deep at its deepest point. An instant hit, the aquarium boasted well over 3.5 million visitors in its first year.

Maintaining a healthy home for the more than 500 species of marine life at GA is a water-treatment facility that would do a small city proud. Designed and built by systems integrator RCK Controls, which specializes in automated control systems for marine environments, it regulates “anything affecting the fish habitats,” says John Hale, RCK’s project manager for the installation.

The aquarium reuses the millions of gallons of water in its exhibits with a complex, closed-loop filtration system that ultimately leaves only small amounts of sludge, which are pure enough to be dumped into Atlanta’s sewer system or local landfills.

More than 3,000 Opto 22 I/O points are at the heart of the automated control system at the Georgia Aquarium.

“We recover all the dirty water we can and get the salt out and recycle it as well. Everything else is retained in house. We go to extreme lengths to keep closed loops,” says Hale.

It’s a system that requires constant monitoring. Water quality, temperature, level, flow rate, oxygen, protein, salt and ozone content, and many other environmental factors all need close attention.

“Some of the species are very sensitive to water temperature, salinity, pH balance, etc.,” says Joe Poniatowski, GA’s life support systems manager. “We have to have very precise control over the water treatment systems.”

A Really Big Deal
Like the challenge itself, everything about the scale of the GA water treatment installation is big. The project took about 2.5 years from start to finish and had a $200-million initial budget.

Underground, below the public areas of the aquarium, are acres containing the water treatment facility—everything from the 65,000-gallon-plus capacity mixing tanks where saltwater for the exhibits is created, to the reclamation tanks that store and recirculate the water in the fish tanks every 90 minutes.

The Ocean Voyager exhibit alone requires 56 25-hp pumps to keep the water moving at 50,000 gallons per minute through the system. The filtration system uses 61 miles of pipe and includes dozens of sand filtration tanks and protein skimmers to clean the water.

Keeping It Clean
Water reuse is crucial to the GA system. The loop for the Ocean Voyager exhibit runs from the saltwater mixing tanks to the exhibits, and then back to the reclamation tanks.

Water from the aquarium is pumped into filter tanks, where it trickles through layers of sand that remove particulates. “As the sand filters start to accumulate debris, we backwash them and blow all the dirty parts into a backwash recovery basin,” says Hale.

In parallel operations, the water is also treated with carbon filters to remove chlorine and fluoride, protein skimmers to remove dissolved organic waste through fractionation, ozone injection and treatment to burn off additional waste matter, and deaeration to remove excess ozone from the water before it goes back into the tanks. In the end, all that’s left is a sludge that is dried and taken to local landfills. All the while, the temperature, level and flow rate of the water have to be carefully monitored.

Mission Control
Manually monitoring and maintaining such a complex system would be a difficult, if not impossible, full-time job, says Poniatowski. RCK’s automated system relieves his 13-person staff, part of which is on duty 24 hours a day, of some mundane responsibilities.

The alternative would be to add significantly more staff to do the monitoring manually, says Hale. “Automation is perfect for these kinds of water quality management systems. Many of the tasks the control system monitors are mundane ones that humans tend to grow bored with. These end up being forgotten, mis-scheduled or done impatiently with brute force, says Hale. Automated controls help moderate costs and problems associated with having a large human staff.

In a sense, GA owes its existence to automated controls. Without them, such elaborate exhibits would be “unfeasible,” says Hale.

The RCK system is a combination of off-the-shelf hardware and custom-designed software—10 RCK custom controllers using 583 analog and 2,523 digital mistic and Snap I/O points from Opto 22.

This whale shark is the largest inhabitant of the Ocean Voyager exhibit that replicates a Central American barrier reef environment. The water in this largest tank in the exhibition is kept at a constant 78 °F.

Control panels are everywhere in the underground facility. The Opto 22 I/O points interpret data, such as the flow rate, and send it to microprocessor cards that read the information and forward it to the RCK system, which controls the processes.

“We use off-the-shelf hardware,” explains Hale. “We needed 3 amp outputs and relays in series. Opto has a solid-state module that will carry 3 amps and last forever. We needed to avoid electromechanical components, which can fail,” he says.

RCK writes its own software because of dissatisfaction with commercially available systems. “We tried various people’s controls, but all of them suffered from lack of support or other limitations, so over time, we started writing our own HMI and add-on code and began accumulating all this expertise. Finally we asked, ‘Why are we messing with this stuff that never is as flexible as we want?’” explains Hale. “We’ve been using our own system for about seven years now. It’s a script-based language from the end-user perspective. It can be modified on the fly. You can see in plain English what’s going on.”

To provide that essential visibility into GA’s critical life-support systems for Poniatowski and his staff, RCK also designed its own graphical user interface to show important system health indicators, such as water temperature, level, oxidation reduction potential and valve operation, as well as alerts to any process problems, directly on computer screens. 

The system uses standard Ethernet-enabled components that communicate over GA’s secure, dedicated Ethernet network, allowing full monitoring from any connected PC or laptop—an added bonus that enables staff to more easily monitor the miles of equipment. Wireless connectivity enables life-support staff carrying handheld computers to receive alarm data instantly.

Ultimately, all that monitoring, controlling, filtering, cleaning and recycling has been worth it. Thanks in part to RCK Controls and Opto 22, the GA has not only become the destination of choice for school field trips and fish enthusiasts and a cool new venue for events from corporate meetings to weddings, but, just as important, a community of 100,000 happy and comfortable fish.