A behind-the-scenes view of the Brookfield Zoo's dolphin pool

This past summer Editor Kirstin Pires and I traveled to Chicago for a tour of the Brookfield Zoo's dolphin habitat. Of course, every one else at the zoo that warm August day spent their time on things like looking at animals and buying souvenirs and cotton candy. We, on the other hand, were there to see and ask questions about the massive sand filters, backwashing schedule and ozone treatment of the marine mammals' habitats.

The tour, led by Dave Derk, supervisor of the zoo's Life Support/Water Quality department, and John Kanzia, Environmental Quality Manager, brought us to parts of the operation ordinary visitors don't get a chance to see and gave us a chance to observe the similarities and differences between their dolphin pool and the pools we usually write about.

The first question we put to our guides was a simple one: How does water treatment for dolphins and seals differ from water treatment in backyard pools? Derk's rather frank answer hinted at the scope of his team's job and what we were about to see.

"The dolphins are getting 100 to 110 pounds of food a day. That's going in and coming out," says Derk. "With kids, you hope they're not going to the bathroom in the water. With the animals, you know they are."

Seven Seas

Brookfield's Atlantic bluefin dolphins are located in a part of the park called Seven Seas, which is also home to the zoo's pinnipeds, a family of animals that includes seals, sea lions and walruses. This article will focus on the million-gallon dolphin area, which includes a large indoor show pool, a medical pool for isolating ailing animals, and holding pools on the north and south ends.

Water from these pools is brought into the filtration room via a 24-inch main line where it's filtered by four 12-foot-diameter sand filters, each with a dedicated pump and 25-horsepower motor. The motors run at 1,800 RPM and are each capable of moving an astounding 1,350 gallons of water per minute.

"We can set in what our flow rates are," Derk explains, pointing to a screen on the newly updated computer system that runs things in Life Support's nearby office and control room. "We play with these values based on turbidity, based on whether they're doing a lot of algae scrubbing and our filters are clogging too quickly. "We have the option to either speed them up to clear the water more or slow them down so they don't clog in the middle of the night."

Despite the massive dirt- and debrisholding capabilities the huge filters connected to these pumps and motors possess, they need frequent backwashing. Each filter is equipped with a flow meter, and once the flow slows to a certain level, the filters are backwashed into the dirty recovery basin, a huge vessel that we stood atop while marveling at the absolutely filthy water it contained. From there, the backwash water is sent through two 5-foot-diameter recovery filters and a foam fractionator until it's clean and can be transferred into the adjacent clean recovery basin.

"The clean recovery basin is then what's used the next time we backwash a filter," Kanzia explains. "We send clean, recovered water to the system. The backwash recovery filters are backwashed to the sewer." This closed-loop system keeps saltwater out of the municipal sewer system, saves the park money and conserves water. "Even though it's dirty saltwater, it's valuable because we have to pay for our salt," Derk says.

Sanitization

After the water's been filtered, 80 percent is sent back to the pools while the remaining 20 percent is separated out and sent to the ozone tower, which is divided by a concrete weir into contact and degas chambers.

"We inject ozone into the contact side through a Mazzei injector," says Kanzia. "The ozonated water then flows over a weir and splashes down into the degas side of the tower. The agitating and splashing action causes the ozone to degas out of the water." Air from the degas tower is then sent though a heating element that breaks the ozone back into oxygen, after which it's vented outside.

"In this facility, we make true ozone," Derk says. "We're taking an O2 molecule, hitting it with 10,000 volts and making O3. That ozone is an unbelievable disinfectant. That one extra oxygen molecule just wants to rip apart viruses, bacteria and everything that we throw at it."

Before zoo operators switched to ozone, Derk says chlorine was the main disinfectant used. "Ozone was becoming more heavily used in institutions across the United States," he explains. "And more and more people realized that it was a superior oxidant that doesn't carry over to the pool if you run it right. "So we just did what everybody else was doing and started backing off on chlorine and increasing the ozone."

Derk's team still uses salt chlorine generators to produce a residual level of chlorine in the dolphin pool as a secondary disinfectant, but they stopped doing that in the 600,000- gallon pinniped pool three years ago after park vets pointed out potential problems for two new fur seals the zoo had acquired. "Our animal people felt it would affect the oil on the coats of the fur seals," Derk says.

"And from what I hear, there were cloudy-eye issues and all the animals seemed like they were a bit uncomfortable with the chlorine in there," Kanzia adds.

Water Testing

Given the amount of waste produced by the dolphins, frequent water testing is a must. Derk and his crew test the water twice per day for chlorine and pH and to make sure the temperature stays around 55 or 60 degrees Fahrenheit, heating and even chilling it when necessary. In addition, Kanzia runs tests once a week.

"I do a full water-quality workup on it. I'll run alkalinity, turbidity and a host of other tests - basically everything you'd check on a home aquarium or pool," Kanzia says. "Then quarterly I'll send out a sample to an outside lab to test for metals, major salts and total organic carbon."

The Life Support team has a lot of tools at its disposal, including the computer system, which closely monitors the parameters the staff tests for. One area where the Seven Seas pools are less automated than many backyard pools, though, is in chemical metering. That's by design, according to Derk.

"We don't have pH control on the system," he explains. "We have the capability, but my fear is that if the pH probe or ORP probe were to break in line, or if it were to get dirty overnight - say a piece of uneaten fish hits it and sits on there - the ozonator is going to skyrocket or it's going to keep pumping our acid inhibitor or our base inhibitor into our exhibits. "The ORP and ozone isn't as critical with the mammals as it would be with the fish, but still I don't want to cook the animals' eyes."

Aside from those factors, the computer drives and monitors everything, Derk says.

"It has an alarm and it can page us, so if in the middle of the night a filter were to get clogged or if we have a power outage, it will alert us," he says. "Also, when we're backwashing, we watch the critical parts of it and we're able to leave the office. But if I walk into the office and everything is beeping, I know something happened. Uh-oh, what's happening?! Then we'll address it."

Dolphins On The Move

One of the major differences between pools at a zoo and those in a backyard (besides the heavy filtration and sanitization load) is that the animals are always in the water. No matter how much use a residential pool gets from kids during a summer heat wave, eventually they're going to come out. And when a homeowner wants to replace equipment or replaster, kids can simply keep themselves occupied on land. Not so with dolphins.

So what does the zoo do with the animals when it needs to perform some maintenance on the pool?

"We're looking at recoating the dolphin pool, and while we're at it we'll be changing out our valves and recoating the insides of the filters - the sand is getting old," Derk says. "So mid next year we'll actually ship the dolphins out to one of the other institutions that we deal with." "I know we were considering Indianapolis," Kanzia adds. "We're also part of a dolphin-breeding program so we may also be able to send them down to Florida."

This process is a lot like you'd imagine, with the dolphins riding in specially designed slings and their handlers keeping them moist and as comfortable as possible.

Kanzia says that the renovation process will take several weeks, after which the dolphins will be returned, none worse for the wear, to the million-gallon pool they call home.