One of the original goals in SBEP’s first Comprehensive Conservation and Management Plan was the removal of surface wastewater discharges to Sarasota Bay. Wastewater discharges contribute excess nitrogen to estuaries, which can cause algal blooms that reduce the amount of light that seagrasses need to grow while also depleting available oxygen for resident fish populations, the major cause of periodic fish kills. In 1990, wastewater contributed about 50 percent of the total nitrogen to Sarasota Bay. When the Comprehensive Conservation and Management Plan was adopted in 1995, the community had already made many improvements to wastewater treatment within the watershed. Nitrogen loads had decreased by 25 percent as a result of enacting the Grizzle-Figg Act of 1990, which required all regional wastewater treatment plants with direct surface water discharge to meet Advanced Wastewater Treatment (AWT) standards. However, several major discharges to Sarasota Bay remained, each contributing excess nitrogen and fresh water to the Bay.
Over time, those discharges have been removed as local governments and state agencies invested millions of dollars in modernizing our region’s wastewater treatment systems. In May of this year, Sarasota County decommissioned the Siesta Key Wastewater Treatment Plant, the last remaining full-time discharge of wastewater to Sarasota Bay. Wastewater from Siesta Key residences is now pumped to Sarasota County’s large treatment facility on Bee Ridge Road.
Because treated wastewater still retains low levels of nutrients, removing any wastewater discharges reduces nitrogen loads to Sarasota Bay. When wastewater discharges were removed from Whitaker Bayou in 2015, nitrogen loads to the Bayou were reduced tenfold. Removing discharges also helps restore salinity regimes in Sarasota Bay, which historically received less fresh water from the watershed than it does today. The City of Sarasota discharged nine million gallons of treated wastewater into Whitaker Bayou every day until the discharge was removed in 2015.
The full story of removing wastewater discharge to Sarasota Bay would not be complete without talking about the “purple pipes” that distribute reclaimed water throughout the region. Reclaimed water is highly treated, disinfected, and purified wastewater that is used for a variety of needs that require non-potable fresh water, such as irrigation, wetlands restoration, groundwater recharge, and industrial applications. Today, approximately 65% of wastewater in the Sarasota Bay watershed is treated and reclaimed for irrigating agriculture fields, golf courses, and newer residential communities, thereby reducing water demand on the Floridan Aquifer.
In general, it is more difficult to create new reuse systems in established urban settings due to aging infrastructure, so reuse rates in these areas tend to be very low. For example, in Southeast Florida counties, reuse rates are less than 10%. In areas with newer development, reuse rates are closer to 100%. According to the Southwest Florida Water Management District, Southwest Florida reuses 54% of its wastewater compared to a 30% average reuse rate across the state.
Florida reclaims more water than any other state in the country. Nationwide, the average reuse rate is only 7%. Still, statewide, Florida communities discharge over 2 billion gallons of variously treated effluent to surface waterbodies. 2008 legislation requires utilities with ocean outfalls to reuse 60 percent of discharge by 2025. As a result, communities with existing ocean outfalls are considering other ways to deal with their wastewater. In Miami-Dade County, construction is underway on a deep-well injection system that will inject wastewater 10,000 feet underground, deeper than any other wastewater injection system in the country.
During the rainy summer months in the Sarasota Bay area, there is not enough surface storage capacity to manage recycled water as demand declines for alternative supply. Therefore, the remaining 35% of the region’s wastewater output that is not reused is treated and sent about 2,000 feet underground into confined deep injection wells underneath the Floridan Aquifer. This method of disposal disperses the impact of the discharge by allowing the water to filter through thousands of feet of karst limestone before reaching other bodies of water, including oceans and drinking water sources.
Treating wastewater involves tradeoffs. Our region’s current system for treating and recycling wastewater reduces nitrogen loads to Sarasota Bay, restores natural salinity regimes in the Bay, and reduces demand for freshwater from the Floridan Aquifer, thus slowing saltwater intrusion into the aquifer. However, environmental risks remain, and preventative measures such as water conservation, advanced wastewater treatment, and planning sufficient treatment capacity for storm events are important to reducing those risks.