Pasco County, Florida, is putting reclaimed water to use in a new way that makes the regional drinking water supply more sustainable and repairs some damage done by past wellfield withdrawals.

The Florida county, which more than 20 years ago committed to reuse 100% of its reclaimed water, built a 176-acre wetland on a cattle ranch to receive excess reclaimed water from five wastewater treatment plants.

Although much of the water is used for irrigation and industrial processes, about 10 mgd was being returned to the aquifer through rapid-rate infiltration basin systems, or RRIBS. County officials thought there must be a better way to handle that water, and ultimately, they built one. Known as the 4G Wetlands Project, it was built at the 4G Ranch, about 35 miles north of Tampa.

Damage undone

“One goal of this project was to take water that was just being infiltrated into the ground and do something good with it,” says Jeff Harris, Pasco County senior environmental scientist. And project manager. “We suffered through decades and decades of environmental harm that was at least in part from wellfield withdrawals. It dried up a lot of lakes and wetlands.”

The 4G Wetlands Project did a lot more than restore dried up wetlands. “It’s a water project, it’s an ecological project, and it’s a reclaimed water management project,” Harris says. The project consists of 15 ponds (wetland cells) of various sizes and shapes that occupy about 133 acres. The entire site, including access roads, buffer zones and berms, covers 176 acres.

The reclaimed water comes in through a 24-inch pipe connected to the Pasco County Master Reuse System, which includes a 500-million-gallon reclaimed water reservoir. The water goes through a manifold with 15 flow-control valves and is distributed to the wetland cells through 8-inch pipes.  

Floating solar-powered sensors on the ponds transmit water-level data to a control panel at the manifold, so the water can be automatically piped to where it is needed most. The wetlands require less maintenance than the RRIBS.

“I’ve often said in presentations that it’s the most dynamic reclaimed water system in the country, maybe in the world,” Harris says. “It’s fed by five treatment plants. It’s advanced secondary treatment, so the nutrients are still in it. That is perfect for golf courses and lawns. It’s completely looped, so we can move water from one part of the county all the way to the other side. It’s a very dynamic system — hundreds and hundreds of miles of pipeline.”

Recharging the aquifer

The ponds are constructed with shallow, deep and transitional areas. They were planted with native vegetation appropriate to the water levels. There are some wet prairies near the tops of the berms and on islands; some areas are dry enough for cypress trees. The water levels are managed to mimic the seasonal hydrological cycle.

“The wetland is located in a watershed upstream of a public supply wellfield,” Harris says. “The water that infiltrates slowly through that wetland ultimately ends up in the Upper Floridan Aquifer and moves downstream toward the wellfield. It provides for a more sustainable water supply.” The wetland was designed to allow infiltration of up to 5 mgd.

While relatively high nitrogen levels in reclaimed water are desirable for irrigation, that is not the case when the water is going back to the aquifer. The wetland solves that problem, too. It naturally denitrifies the water.

“It’s a fantastic biological process,” Harris says. “In the root zone of the plants in the wetland, bacteria eat all that stuff up. Sometimes it can be converted to atmospheric nitrogen through plants. As the water percolates down through those soils, the bacteria eat it up. By the time it gets to even the surficial water table, it’s almost background nitrogen level. That’s the intent.”

Careful selection

The site was chosen after a long, careful search. “We rated hundreds of parcels,” Harris says. “We narrowed it down to the ones that would work, and we approached those property owners. At the 4G Ranch, the owner understood the need, and he wanted to partner with the county. It was his desire to bring back some of the lakes on his property.

“It was dry before we came out and built the project. It had been dry for decades. There were two dry lake beds. Cattle could get from one side of the ranch to the other without having to walk around the lakes. In times of drought, the ranch owner would have to dig huge burrow pits just to water his cattle.”

It was dry enough that operating earthmoving equipment on the site wasn’t a problem. Soil was scraped up from the pond beds to make berms around each pond. The berms are about 4 feet above grade level and are 10 feet wide and flat on top.

“We built a wetland on an upland, as funny as that sounds,” Harris says. In addition to the wetlands created, the project lifted the surficial aquifer, to the benefit of hundreds of acres of nearby wetlands that had been degraded from wellfield withdrawals. The 4G Ranch still has cattle, but they don’t walk through the ponds. The berms are protected by split-rail PVC fencing with hog fencing between the rails to exclude cattle and feral hogs. “We don’t want animals in there destroying berms,” Harris says.

Model for future

Pasco County officials expect this $14 million project to be a model for future projects because of the public-private partnership and the multiple benefits: wildlife habitat, a more sustainable water supply, ecological restoration and improved management of reclaimed water. In May 2017, the project was named Reuse Project of the Year by the Florida Water Environment Association.

“We built true natural wetlands,” Harris says. “They’re beautiful. We host tours. We bring public agencies out. Soon we’ll be taking school kids out to show them what ecology looks like and how we can leverage technology and engineering to reform nature.”