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Water, United States, North America, Government, Integrated Resources Management, Water Reuse
Balancing Act
Meeting Water Supply and Environmental Needs in Miami-Dade County
Supplying drinking water for residents while also protecting the environment is a serious challenge for utilities in South Florida. Population continues to grow and new regulations to protect the environment are becoming more stringent. Sustainable approaches to water management and integrated plans that incorporate alternative water supply projects are necessities to meet human and ecological needs.
“SDWRP will use the same treatment process as the award-winning Orange Country groundwater replenishment system…It’s rewarding to use lessons learned in California and adapt them to the complex geographic and regulatory environment of Miami-Dade County.”
Bruce Chalmers, CDM Smith vice president
The Miami-Dade Water and Sewer Department (MDWASD) currently relies on the Biscayne aquifer—which is hydraulically connected to the Everglades National Park—to supply more than 300 million gallons per day (mgd) of drinking water for most of Miami-Dade County. However, a comprehensive effort by the state and the South Florida Water Management District (SFWMD) to restrict any increase in water withdrawals from the Lower East Coast Everglades Waterbodies has prompted the need to offset any increase in water pumping from the aquifer.
“We must balance the need to supply drinking water to approximately 2.3 million consumers with meeting the district’s requirement to replenish the aquifer with an annual average of 18.6 mgd using advanced and proven treatment technologies,” explains Bertha Goldenberg, MDWASD assistant director.
Big Plans, Huge Savings
For more than 20 years, CDM Smith has been working with MDWASD to meet the area’s water and wastewater needs. In 2006, the team began work to assess the service area water demands, meet regulatory requirements, and implement sustainable water supply measures to obtain a 20-year consumptive water use permit with SFWMD. In addition to aquifer pumping regulations, planning had to consider state legislative pressure to eliminate the disposal of municipal wastewater effluent through ocean outfalls.
According to Ken Caban, CDM Smith project manager, “We had to figure out how much water MDWASD would need for the next 20 years and how to get it, while promoting environmental sustainability. We considered all options, including drawing water from the deeper Floridan aquifer, blending various source waters, reuse and conservation.” By presenting a comprehensive outline of innovative and alternative water supply projects to meet the projected demand, MDWASD successfully met approval requirements for its permit.
Unexpected Declines
While developing a 20-year master plan, the team discovered that Miami-Dade County was experiencing reduced water demands from those originally projected in the permit. Several factors led to the reduction, including MDWASD’s aggressive water conservation program, water system operational adjustments, SFWMD’s irrigation water use restrictions, and an increase in the number of days with rainfall.
“The benefit was that we could update water demand projections in hopes of modifying the water use permit and delay or eliminate $1.3 billion of capital improvements,” emphasizes Caban. MDWASD continues to improve its water conservation program and has incorporated a reduced-pressure alternative—which attempts to reduce overall water system pressures by decreasing discharge pumping at plants—into its master planning in hopes of yielding additional water demand reductions.
The Rewards of Reclaimed Water
One alternative water supply project in progress is the South District water reclamation plant (SDWRP). CDM Smith is leading the design team for the 21-mgd plant, which will be the first of its kind in Florida. SDWRP will treat filtered secondary effluent from the South District wastewater treatment plant using microfiltration, reverse osmosis, ion exchange ultraviolet light and advanced oxidation. Near-distilled quality effluent will then be pumped 6 miles to the Miami Metro Zoo, where it will be discharged into groundwater via injection wells to recharge the Biscayne aquifer.
“SDWRP will use the same treatment process as the award-winning Orange County groundwater replenishment system [designed by CDM Smith and put into operation in 2008]. It’s rewarding to use lessons learned in California and adapt them to the complex geographic and regulatory environment of Miami-Dade County,” says Bruce Chalmers, CDM Smith vice president and SDWRP project manager.
Reclaiming water uses a previously untapped resource and benefits the environment by reducing ocean discharges and augmenting drinking water supplies. With the capacity to produce 21 mgd for groundwater recharge, SDWRP can surpass the district’s aquifer replenishment requirement. In addition, the design team is working closely with state and local regulators to monitor SDWRP’s water quality.
“Completion of SDWRP will be a significant milestone in the department’s wastewater treatment and disposal history, and chart a new course for reclamation practices in Florida,” notes Vicente Arrebola, MDWASD assistant director.
Modeling the Future
SDWRP is one important element of Miami-Dade County’s comprehensive master plan. With the assistance of hydraulic modeling, CDM Smith will incorporate energy efficiency and a triple-bottom-line approach to sustainability throughout many of the proposed projects, including measures to mitigate climate change. “It is our responsibility to protect future generations by proactively conserving water and protecting the environment. Miami-Dade’s integrated approach to water resources planning will be a showcase in the region and world for years to come,” adds Ignacio Lizama, CDM Smith associate and client service manager.
Doug Yoder, MDWASD deputy director, concludes, “We no longer have the option to consider water, wastewater, and reclaimed water as independent resources. MDWASD is at the forefront of integrated water supply planning by balancing all of these elements for the daily benefit of our residents.”
