Conserving Water by Using Another Source: Reclaimed Wastewater

GAINESVILLE, Fla. — With Florida’s potable water resources facing increased strains from factors like an ever-expanding population and saltwater intrusion, University of Florida researchers say relief could come from an increasingly abundant source: reclaimed wastewater.

“The general public needs to be aware that reclaimed wastewater is an option that can be cost-effective and conserve our water resources,” said Kimberly Moore, an environmental horticulture professor at the UF Institute of Food and Agricultural Sciences. “If homeowners can reuse more wastewater while maintaining a successful landscape, then they won’t need to pump as much from the aquifer, conserving water and reducing the potential for saltwater intrusion.”

Two plants are part of Kim Moore’s experiments at the Fort Lauderdale Research and Education Center. One has received 200 ml of tap water, left, and the other the same amount of wastewater. (courtesy of Kim Moore, UF/IFAS)

Much of Moore’s research at the UF/IFAS Fort Lauderdale Research and Education Center has focused on applying reclaimed water to grow containerized plants, which she hopes will eventually inform the greenhouse nursery industry on how to best utilize this water resource.

Wastewater is treated in a two- to three-step process. The first two steps remove solid wastes and contaminants; the third “advanced treatment” stage further purifies the water, although some nutrients, such as nitrogen and phosphorus, will remain after advanced treatment. The treated wastewater is then kept in tanks that are open in many facilities, meaning the nutrient levels could potentially be diluted during rainier seasons.

All wastewater treatment facilities in the state must adhere to a standard minimum level of treatment, Moore said, but the problem – and the reason for her research – is that the remaining nutrients can vary and may still be too much for certain plants to handle.

“We discovered that it’s really more the sodium in the water than it is the other nutrients that affect how well a plant grows,” said Moore, whose latest tests are investigating the salt tolerance of various foliage plants. “The plant is going to take up much of the nitrogen, phosphorus and other useful nutrients, but it doesn’t like the sodium.”

But Moore said her region is also lacking much of the infrastructure to pump reclaimed water to those who may wish to use it.

On the other side of the state, the Tampa Bay region was among the earliest adopters of laying the necessary purple pipe to transport treated wastewater, said Mary Lusk, an assistant professor in the UF Soil and Water Sciences Department based at the UF/IFAS Gulf Coast Research and Education Center in Hillsborough County. Lusk’s research involving reclaimed water centers around its residential use.

“In the Tampa Bay area, there are a lot of communities that are entirely irrigated with reclaimed water, and it’s expanding,” Lusk said. “My larger research question deals with sources of nutrients to urban stormwater runoff, which can be many things – fertilizer, pet waste, even just the atmosphere – but it can also be reclaimed water when it’s used for irrigation and people over-apply or water the sidewalks.”

Reclaimed water users in residential settings should be sure to apply as recommended, she said.

“Reclaimed water should not be used for recreational activities, like a kids’ pool or sprinkler, or applied to any food product that is not going to be skinned, peeled, boiled or cooked in some way,” Lusk advised. “There are absolutely no documented cases in Florida of harm from such uses, but we err on the side of caution.”

She emphasized the value in using reclaimed water, though, in the correct way.

“Treated wastewater does contain nutrients, and if it’s not sent back into the community for reuse somehow, the usual way of disposing of that is to discharge it into our water bodies,” Lusk said. “We need to use this water, but we need to use it wisely.”

Paving the way for more people to best use reclaimed water is important, Moore said.

“I hope that my research helps wastewater treatment facilities determine a standard nutrient level range,” she said. “Especially for the greenhouse industry and containerized production, growers expect a consistent product of a certain quality if they are going to use reclaimed water and use it effectively.”

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The mission of the University of Florida Institute of Food and Agricultural Sciences is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS works to bring science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents. Visit the UF/IFAS website at ifas.ufl.edu and follow us on social media at @UF_IFAS.

Click to view full-sized infographic. (UF/IFAS)

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