The heavy rains that flood streets and wash out beach parties in Destin, Fla., don’t bother Richard Griswold. In fact, they can make him happy, since the precipitation fills his utility’s underground storage and recovery system with water, which then can be used for irrigation around the community.

“Storage is critical,” says Griswold, general manager of Destin Water Users Inc. (DWUI). “Unlike drinking water, which follows a preset law of supply and demand, there are no guidelines for reuse. It’s a different animal altogether. Demand can exceed supply. We need to make the supply of reclaimed water reliable; otherwise, people will not use it.”

That’s why rainy days are welcome within Griswold’s agency and its George French Water Reclamation Facility. “We anticipate oncoming rain days and figure out what we can do with the water,” he says. “On a normal day, 100 percent of the wastewater we treat is going out as reclaim. We look for heavy rainfall days when we can actually store water for future reuse.”

Simple process

While total water reuse and the underground recharge system set Destin apart from many other utilities, the agency’s water and wastewater treatment infrastructure is fairly typical. At six square miles in area, Destin sits on a densely populated island between Choctawhatchee Bay and the Gulf of Mexico on the Florida Panhandle. About 20,000 residents live there in winter, but the population swells to 60,000 during the summer fishing and tourism season.

The community draws drinking water from the Upper Florida Aquifer, which Griswold says is both “sweet” and prolific. DWUI operates five deep coastal wells and partners with other communities on an inland wellfield. Each well has its own chlorine injection system, and after onsite disinfection, the water is pumped into the distribution system. Total flow is about 6 mgd.

The community’s wastewater enters the treatment plant through two step screens (Spaans Babcock). The water then flows into an equalization basin and is pumped to a series of racetrack-type oxidation ditches (WesTech) for biological treatment. From the ditches, the water flows to six circular clarifiers outfitted by WesTech.

Three screw pumps (Spaans Babcock) lift the clarified water to six mixed media traveling bridge filters (four by Infilco Degremont, two by Ovivo) which are followed by chlorination. Almost all of the treated water is reused for irrigation by the homeowners, commercial property owners, condominium developments and golf courses. It is stored either in above-ground tanks (6.75 million gallon capacity) or in a new underground storage and recovery basin. A portion is returned to the treatment facility for equipment washdown.

Aerobic digesters process the biosolids. Waste solids are thickened with polymer and then dewatered to a 15 percent cake on a belt filter press (Ashbrook). The material is hauled to a privately operated land application site, shared with several other treatment agencies, where it is recycled as a soil amendment for hay crops.

Recognized for excellence

Destin has been honored with a 2000 U.S. EPA Region 4 reclaim water Award of Excellence and has been recognized many times for its safety record by state and regional organizations. “It’s part of our culture,” says Griswold. “We talk about safety on the first day and every day. All our managers are responsible for it. We just make it happen.”

Destin has a safety committee, important enough to have its own charter within the DWUI utility. The committee’s goals aren’t just the usual statements about the number of lost time accidents. “We don’t focus on that,” says Griswold. “Rather, our concern is identifying the issues that endanger our employees and the public, and how we can minimize those.”

It’s an approach that differs quite a bit from the time when Griswold joined the utility 14 years ago. “Back then, safety was just left up to the employees, and the budget for safety was zero,” he says. “When I came here, the big issue was which department was going to pay for the yellow paint to mark safety hazards. Now we put safety in the budget. The directors approve it without much discussion, and the program is off and running.”

The utility’s maintenance program is also undergoing modernization. For years, according to Griswold, Destin has relied on experienced plant operators to maintain the pumps and other equipment, but that history is slipping away as older employees retire. DWUI is replacing that institutional memory with a more programmatic asset management program.

“In the old days, department managers simply knew what had to be done,” he says. “That worked fairly well because we had employees who knew everything they needed to know. Now we’re building a database. We started by using GIS, but as asset management software developed, good packages became available to use.” Destin chose a system from Cityworks.

Griswold’s operation has taken a similar step-by-step approach to energy consumption. “We had an audit, but the report really didn’t recommend anything we weren’t doing,” he says. “We’ve looked at aeration and diffusers, but it’s a hefty cost at first and the payback is 20 years.”

Instead, Destin has installed variable-frequency drives nearly everywhere and uses soft starts on pumps and other machinery. “We’ve also looked at our buildings, upgrading insulation to reduce HVAC costs, and converting to LED lights where we can,” says Griswold. “We’re taking the low-hanging fruit, doing a little bit at a time.”

Aquifer storage and recovery

The underground storage and recovery system is Destin’s pride and joy. “We started working on it in 2000,” says Griswold. Work has proceeded slowly, in parallel with development of the regulations, but at present seven wells are operating, each at 250 gpm in and out.

Above-ground storage is expensive and requires space. “We have a shallow aquifer here,” Griswold explains. The storage wells are about 160 feet deep, and the entire soil complex is sand. “It’s an excellent storage system. The reclaimed water forms a bubble around the tip of the well.” As the bubble grows, Destin hydrogeologists can identify the interface between the reclaimed water and the natural groundwater, which serves as a barrier to saltwater intrusion. As demand exceeds supply, the bubble can be tapped to provide additional reclaimed water.

“Anyone who thinks they can design a new reclaimed water system and make it efficient doesn’t know what they’re talking about,” Griswold says. “You can’t plan for all the conditions you’ll face. You don’t see these lessons in the textbooks, where there’s more information on how to make reclaimed water than what to do with it. There are no guidelines for reuse, no annual average days. Demand can exceed supply. You guess and hope you’re right.”

In addition to the underground storage capacity, DWUI works with customers on water conservation. “We’ve learned the value of conservation of reclaimed water,” Griswold says. “We spend a lot of time with our customers on how best to conserve. Overwatering is as bad for a landscape as underwatering. We talk about that. Our reuse coordinator goes out and helps set timers on residential watering systems.”

That’s just one of the reclaimed water lessons the Destin utility has learned. Another is the value customers place on reclaimed water. “Customers value reclaimed water more than they do drinking water,” Griswold maintains. “We had a huge drinking water outage here at one time and didn’t get a single call or complaint from our customers. But when we had an issue with the reclaimed water system, the phone rang constantly. People were mad. I’ve learned that a reliable supply of reclaimed water is critical to the success of the system.”

Which takes the discussion back to rainfall. Because of the need to keep the reclaimed water supply at adequate levels, Destin keeps a close eye on the weather. “We get 52 to 58 inches of rainfall a year,” Griswold says. “It’s been pretty normal lately.” But just to be safe, DWUI has installed its own weather station. That way, Griswold says, there’s no need to rely on outside sources for vital data.