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Adding Treated Wastewater To Aquifer Considered

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By MIKE SALINERO

The Tampa Tribune

Published: September 23, 2008

TAMPA - Regional water managers are spending a half million dollars researching whether Hillsborough County should inject millions of gallons of treated wastewater into the vast underground lake known as the Floridan Aquifer.

If Hillsborough adopts the practice, called aquifer recharge, it would become the first county in Florida to use the technique.

Aquifer recharge is a way to reuse wastewater now dumped into rivers and bays. The injections would stop saltwater from flowing into the aquifer at the coast and bolster groundwater supplies to meet future population growth.

The Southwest Florida Water Management District is studying the concept, which originated in California more than 30 years ago. The study should be done by the end of March.

"We're not asking to build it or get it permitted" right now, said Dave Moore, the water district executive director. "We're asking: What are people doing around the country or around the globe and do something similar here that's safe for the environment and creates additional water supply."

Rainwater that seeps underground in Florida is carried like a conveyor belt toward the coast, where it escapes the aquifer through springs and seeps. Moore said if highly treated wastewater could be injected near the coast, it would allow more groundwater to be pumped farther inland.

"If you can put a gallon of reclaimed water in, you can take out a gallon of water for processing on somebody's water-use permit," said Steve Daignault, Tampa's director of Public Works and Utilities.

Is It Cost-Effective?

A key question the district must answer is whether recharge is the most cost-effective way to increase water supplies. The wastewater would have to be treated to drinking water standards before state authorities would allow it in the groundwater, an expensive proposition. Moore estimates a 40-million-gallon-a-day reclamation plant with the best treatment methods would cost $200 million or more.

Other unknowns: Where are the best places to inject the wastewater, and what areas would be given credits to pump more groundwater that would be offset by the aquifer injections. Some areas in Polk County and southern Hillsborough are limited in how much they can pump because of depleted groundwater levels there.

California pioneered aquifer recharge in 1976 with the opening of Water Factory 21 in Orange County. The plant treats sewer water to drinking water standards, then mixes it with deep-well water. The combination is injected into aquifers prone to saltwater intrusion.

This year, Orange County began operating the world's largest water reclamation plant, a facility that can turn 70 million gallons of treated sewage into drinking water every day. The end product is injected into the groundwater basin.

The continuous infusion of treated wastewater allows Orange County to produce more drinking water for its 2.3 million residents, replacing sources from outside the county that are becoming unavailable. No environmental or public health problems have been linked to recharge.

Development, Drought Force Issue

Florida is struggling with some of the same challenges that forced California to seek alternatives to groundwater pumping in the 1970s. Rapid population growth and frequent droughts have depleted Florida's once-abundant groundwater supply, drying up lakes and springs.

One answer, everyone agrees, is better use of reclaimed water.

In Tampa, 60 million gallons of treated wastewater is dumped into Tampa Bay daily. The water's high nitrogen level is causing state environmental authorities to threaten the city with fines if it doesn't limit discharges.

Tampa was working with Hillsborough County, Tampa Electric Co. and Mosaic Fertilizer on a proposal to pipe the city's effluent east for the expansion of TECO's Polk Power Station. The pipeline was to pass an abandoned Mosaic mine where an aquifer storage project was contemplated.

TECO officials decided the pipeline from Tampa to Polk County was too expensive. The company is now talking to Plant City, Lakeland and Polk County about buying their reclaimed water. The recharge project at the Mosaic mine is still on the table.

Phil Compton, who works on local water issues for the Sierra Club, said aquifer recharge might work as long as the water is cleaned up sufficiently before it is injected underground. "I think it's definitely something worth studying. If they put it in the aquifer there should be some additional filtration. It may be a more cost effective way and would do a better job of removing the remaining contaminants."

Reporter Mike Salinero can be reached at (813) 259-8303 or msalinero@tampatrib.com

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