Reverse Osmosis Treats Aquifer Water

It's a way to quench deep thirst of growing populace

GEORGE ANDREASSI / The Stuart News (Florida) 30dec03

JENSEN BEACH -- Four football fields below the earth's surface, smelly, brackish water lies amidst fractured limestone in the Floridan Aquifer.

Through a process known as reverse osmosis, which removes salt and other impurities, that slimy, undrinkable liquid is converted into clean water at Martin County's North County Water Treatment Plant near Pineapple Park.

Tapping water from the Floridan Aquifer and treating it through reverse osmosis is the wave of the future to meet the needs of the growing populace in Martin County and the rest of the Treasure Coast, county and state officials said.

"It's very good, very high-quality water," said county Utilities Director John Polley. "The fact that we do use reverse osmosis and membrane softening not only takes out things that could contaminate the water, like bacteria and pesticides, it also removes the items that can lead to taste and odor problems."

How to provide water for the steadily growing population is a longstanding issue throughout Florida. Building reverse osmosis water treatment plants that tap into the Floridan Aquifer is helping Martin County, Port St. Lucie and other local governments meet the growing need for drinking water.

The Martin County Commission is expected to award a $15 million contract in January for a new reverse osmosis water treatment plant in Tropical Farms, Polley said.

After the plant is completed in December 2005, all of Martin County's 25,000 water customers are expected to be using water that originates mainly from the Floridan Aquifer, Polley said.

That will dramatically reduce the demand for water from the Surficial Aquifer, which is located less then 150 feet below the earth's surface and is the source of water for most private wells, Polley said.

Overpumping the Surficial Aquifer could damage environmentally sensitive wetlands by lowering the groundwater water table, state and county officials said. Wells supplied by the Surficial Aquifer are also subject to salt water intrusion and pollution from contaminated runoff.

The new water treatment plant in Tropical Farms is required by the county's master development plan, which says that new water treatment facilities must be designed when demand reaches 70 percent of capacity and built when demand reaches 80 percent of capacity, Polley said.

The Martin County water system is capable of producing 12 million gallons per day and the demand is 9.4 million gallons per day, county records show. That means demand is at more than 78 percent of capacity.

The expansion at the Tropical Farms Water Treatment Plant that includes tapping into the Floridan Aquifer for raw water will enable the county to phase out old-fashioned Surficial Aquifer supplied facilities in Palm City and Port Salerno, county officials said.

The Martin Downs Water Treatment Plant was built in 1982 and the Vista Salerno Water Treatment Plant was built in 1984.

Those older plants are expected to have increased difficulty meeting state and federal regulations in the future as standards become stricter, Polley said.

After those water treatment plants are shut down, the facilities in Tropical Farms and Jensen Beach, which were linked in July by pipes laid beneath the St. Lucie River, will serve the county's water needs for the next 10 years.

Drawbacks remain

There are drawbacks to the reverse osmosis technology.

A reverse osmosis water treatment plant costs more than twice as much to build as an old-fashioned lime-softening filtration system, which uses water from the Surficial Aquifer, county officials said.

Another controversial aspect of the reverse osmosis process is the use of deep-well injection to dispose of the waste products leftover by the process. The wells are about 3,000 feet below the earth's surface and some environmentalists fear the waste products will seep back up into the aquifer and contaminate the water supply.

But Polley said utility industry officials have confidence that the deep-well injection process, which is regulated by the federal and state governments, is environmentally sound.

Another benefit of the reverse osmosis water treatment plants is that they are mainly computer operated, Polley said. That means fewer workers are needed.

In addition to replacing the water currently produced by the older facilities, the expansion of the water treatment plant in Tropical Farms is needed to serve new development, Polley said.

In recent years, the county has also provided water service to hundreds of homes in several older communities that had been served by antiquated private utilities. They include Woodside and Fox Run in Palm City, Leilani Heights and Fisherman's Haven in Jensen Beach, and Pinelake Gardens and St. Lucie Settlement in the central part of the county.

Another 150 homes in Port Salerno have been connected to the county water system because of contamination in the ground water from the old Solitron toxic waste site on Cove Road.

In addition, hundreds of homeowners in Old Palm City will be allowed to hook up to the county water system for free next year because of the petroleum related contamination in the ground water in their neighborhood.

Connection encouraged

County officials also try to encourage property owners within the urban area who rely on wells and septic tanks to connect to the county utility system to reduce the pressure on the Surficial Aquifer.

Reducing the county utility's reliance on the Surficial Aquifer should also benefit environmentally sensitive wetlands, state and county officials said.

The county built the reverse osmosis treatment plant in Jensen Beach in 1993 to tap into the Floridan Aquifer because of concerns that the old system was drawing so much water out of the Surficial Aquifer that the nearby Savannas were being impacted, said Jim Mercurio, the county's treatment superintendent.

The water from the reverse osmosis water treatment plant is mixed with water produced by the lime-softening filtration plant built in 1982, county officials said.

The final product is collected in massive storage tanks before being pumped through pipes beneath the streets of Jensen Beach, Hutchinson Island and Sewall's Point, eventually flowing out of the taps of local homes and businesses.

Plant opened in April

South Martin Regional Utilities, which serves about 8,000 water customers in Hobe Sound and Jupiter Island, opened a reverse osmosis water treatment facility in April that produces two million gallons per day, said Utilities Director Gene Rauth.

The Fort Pierce Utilities Authority put a new reverse osmosis water treatment plant on line in December 2002, officials said. The plant pumps five million gallons of water per day. The City of Port St. Lucie started operating a reverse osmosis facility in 1999 that pumps 10 million gallons per day, and another facility is under construction.

By tapping to the Floridan Aquifer for water, the utilities are following the advice of the South Florida Water Management District, a state agency that regulates the local water supply.

The state's water supply plan for the Treasure Coast encourages utilities to move away from pumping water out of the Surficial Aquifer and toward tapping the water in the Floridan Aquifer, said Mark Elsner, a top planner with the water management district in West Palm Beach.

"We consider that the Surficial Aquifer system in much of the coastal area up there is maximized," Elsner said.

- george.andreassi@scripps.com

source: http://www.tcpalm.com/tcp/the_news_local_news/article/0,1651,TCP_1028_2539696,00.html 30dec03