July-August 2009

Using Water More Than Once

Working together to protect the water supply and the environment

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Photo: City of Boca Raton

By Diane Gow McDilda

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It’s rare for a project to satisfy multiple parties and alleviate a range of environmental concerns, but for one water reuse project in South Florida, the benefits are various and sundry. From reducing demand on potable water, to improving coastal water quality and even helping to guard against salt water intrusion, the city of Boca Raton’s reclaimed water initiative illustrates that regulators, municipalities, and private industry can collaborate with everyone’s interest at heart.

“Boca Raton is setting a great example in an area that has lagged behind the rest of the state in reuse,” says Mark Elsner, P.E., a director in the water supply department of the South Florida Water Management District (SFWMD). “Reuse is an integral part of water resources management, wastewater management, and ecosystem management in Florida. It reduces demands on valuable surface and groundwater used for drinking water sources, eliminates discharges that may pollute valuable surface waters, recharges groundwater, and postpones costly investment for development of new water sources and supplies.”

Man’s Hand
With 53 inches of rainfall annually, how is it that South Florida isn’t awash in water? At one time, it was. Where summer showers once fell on swamps and slowly replenished underlying aquifers, the quick-and-plentiful rains are now channeled away from residents and businesses through storm drains and canals that border shopping centers and cut through subdivisions. As the population rises and irrigation continues to draw water, supply management becomes more crucial.

Photo: City of Boca Raton
Boca Raton has become home to a population of 86,000 people, along with affluent gated communities and high-end golf and country clubs.
The coastal community of Boca Raton spans 29 square miles of mainland and spits of land wedged between the Atlantic Ocean and Intercoastal Waterway. It is home to a population of 86,000 people, along with affluent gated communities and high-end golf and country clubs. And until severe droughts in 2001, and another in 2007, water was considered bountiful.

In 2001, water levels in Lake Okeechobee dropped to a record low of 8.97 feet, this in a lake with an average depth of 9 feet. Lake Okeechobee, covering 730 square miles, is the second largest lake in the US. Its drainage basin spans 4,600 square miles, and it’s a source of drinking water for lakeside communities and a backup supply for others in the southeastern part of the state, like the city of Boca Raton.

The 2007 drought saw similar low water levels, further straining water supplies and leaving channel markers in the lake high and dry. It also instigated mandatory Phase II water restrictions, which are only implemented during severe drought. In an effort to shrink demand by 30%, watering was restricted to limited times—twice a week for residents and businesses, including golf courses. For the 22 golf courses in Boca Raton, this meant the rough was truly rough—and brown.

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Water is provided by the City of Boca Raton Utility Services, but water management for the city is under the authority of the SFWMD. The SFWMD is one of five water management districts in Florida, and is responsible for water quality, flood control, water supply, and environmental restoration. It’s the oldest and largest district, and spans the southern tip of the state from Orlando to The Florida Keys. The city of Boca Raton, within Palm Beach County, lies within an area designed as the Lower East Coast (LEC), for water supply planning. Other areas within the SFWMD’s jurisdiction surround Lake Okeechobee and include the Kissimmee Basin, Upper East Coast, and Lower West Coast.

The LEC spans 6,100 square miles and, along with Palm Beach County, includes Miami-Dade County, most of Monroe County, and the eastern portions of Hendry and Collier Counties. Water in the LEC is supplied by the surficial aquifer system and the Biscayne Aquifer, along with surface water from the Everglades and Lake Okeechobee. Next Page >

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edo

August 1st, 2009 5:17 AM PT

Recycling water is the wave of the future but it must be done carefully for critical public health reasons. It would be interesting to watch this project over time with an epidemiological overlay for the spread of antibiotic resistance into the community. I doubt, however, that the system is set up for gathering such data. Illnesses complicated with antibiotic resistance, especially in the elderly, see added costs and prolonged recovery times. Today, complications from antibiotic resistant organisms cause more deaths than AIDS. Nonetheless, removal of antibiotic resistance carrying microbes and their genetic fragments from reclaimed water has proved to be difficult. For example, along with their $500 dollar hammers, those attempting to supply clean water for long-term space travel have run into problems with antibiotic resistance. The Johnson Space Center evaluated antibiotic resistance in two water reclamation systems developed for space missions. To their surprise, the study results indicated antibiotic resistant bacteria in all systems were resistant to many antibiotics including beta-lactam antibiotics and a beta-lactam, beta-lactamase inhibitor combination, amoxicillin with clavulanic acid (see: http://www.springerlink.com/content/vr3355q13g3571t6/ ) In running lab analyses out here in California on reclaimed (recycled) water, we are finding two issues that consistently crop up. The first is that multi-antibiotic resistant bacteria are noted in the finished reclaimed (recycled) water. The second is that the farther out in the system, the higher the counts of indicators. As an example of the second case, we tested reclaimed water that met all applicable standards for California recycled water at the plant before being put through the delivery system. The water tested out as non-detect. Then we went to the point of use (POU) and retested the water. At POU, using a simple most probable number (9-tube, PR lactose in Durham tubes) we noted that all tubes were positive. Interestingly, the numbers that are used for this test do not go that high, i.e., the indicator bacterial numbers at the POU were off the chart. This kind of result merely shows the serious public health implications in using standard tests to look for organisms that may be pathogens or carry antibiotic resistance. The tests used generally throughout the industry are not capable of demonstrating that the water is safe, merely that certain indicators are not above specified limits. This was the conclusion of the work done by Valerie Harwood and Joan B. Rose, which included tests on finished reclaimed water from Florida (see: http://aem.asm.org/cgi/content/abstract/71/6/3163). In their work, Harwood, et al note: Microorganisms were detected in disinfected effluent samples at the following frequencies: total coliforms, 63%; fecal coliforms, 27%; enterococci, 27%; C. perfringens, 61%; F-specific coliphages, 40%; and enteric viruses, 31%. Cryptosporidium oocysts and Giardia cysts were detected in 70% and 80%, respectively, of reclaimed water samples. Viable Cryptosporidium, based on cell culture infectivity assays, was detected in 20% of the reclaimed water samples. No strong correlation was found for any indicator-pathogen combination. When data for all indicators were tested using discriminant analysis, the presence/absence patterns for Giardia cysts, Cryptosporidium oocysts, infectious Cryptosporidium, and infectious enteric viruses were predicted for over 71% of disinfected effluents. The failure of measurements of single indicator organism to correlate with pathogens suggests that public health is not adequately protected by simple monitoring schemes based on detection of a single indicator, particularly at the detection limits routinely employed. Dr. Edo McGowan

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