The 756,000-gpd Plantation Bay Water Treatment Plant was built by a private developer in the 1980s to serve approximately 1,600 residents of a residential community along with a private community golf course. Over the years, the facility had degraded and the original lime softening treatment process was no longer effective enough to maintain regulatory compliance and to meet other aesthetic goals. Other challenges included:
- A groundwater supply with high organic content resulted in finished water that periodically exceeded the MCL of 80 µg/L for TTHMs
- High color in the groundwater supply (approaching 90 color units), resulted in customer complaints and the shutdown of two of four wells
- High iron levels
- Water hardness (~325 mg/L as CaCO3)
Flagler County purchased the facility in 2014 with the goal of improving water quality and bringing the facility back into regulatory compliance. To accomplish this, the county implemented a nanofiltration (NF) system. NF is ideally suited to remove dissolved constituents such as hardness, color and TOC. The new treatment process also includes oxidation, pressurized multi-media filtration, pH adjustment, antiscalent, cartridge filtration, and disinfection. A partial NF bypass stream was designed to add pH and alkalinity to the permeate water, resulting in lower chemical usage and operational costs. The system is designed to include a 2-stage NF system with an overall recovery of approximately 80%.
Concurrent with design, a four-month pilot test was performed. Based on the results of the pilot study, the county commenced with construction.
Since the chloride levels of the water supply are so low (~25 mg/L), the NF can be beneficially reused for golf course irrigation with no damage to plants, grass and other landscaping. The concentrate is sent to the effluent stream of the Plantation Bay Water Reclamation Facility, where it blends with reclaimed water to supplement the County’s reclaimed water system and used by a local golf course. This eliminates the need for concentrate disposal through deep well injection or surface water discharge.