Water Supply Restoration Program

Filter Systems

 

Point of entry (POE) filters are installed when there are potential health risks associated with dermal contact (washing hands) or inhalation (Breathing the fumes coming from the water). Examples of these substances include pesticides, petroleum compounds, and solvents. Granular Activated Carbon (GAC) filters are the most commonly used POE filter systems installed on wells contaminated with these substances.

Point of Use (POU) filters are installed when the only potential health risks are associated with drinking the water (generally, inorganic substances such as nitrate or lead). The WSRP generally uses reverse osmosis systems installed under the kitchen sink for these contaminants.

Granular Activated Carbon

FDEP currently maintains approximately 1,185 of these systems, about 80 percent of which are operating on EDB (a pesticide contaminant) contaminated wells. There are approximately 150 filters currently operating on wells contaminated with solvents and approximately 110 filters on wells with petroleum contaminants.

Performance data for carbon filters indicates that these filters perform extremely well for most groundwater contaminants. The configuration of each installation is determined by the removal efficiency for that particular contaminant and the expected flow demand.

Because carbon is so effective at removing EDB, the most common filter system used for this contaminant consists of a five micron pre-filter, a flow meter, a single 54-inch tall by 10-inch diameter GAC tank, and an ultra-violet light for disinfection. This system has a capacity of 6 gallons per minute (gpm) and is sufficient for the average home.  The filter media for all systems installed for EDB is exchanged annually.

GAC filters are very successful in removing solvents or petroleum products. Filtering out Vinyl Chloride (VC) or Methyl-Tert-Butyl-Ether (MTBE) is more of a challenge. Filters on wells with VC are exchanged every six months and filters on wells with MTBE continue to be sampled quarterly and exchanged after a breakthrough at the mid-point.

Reverse Osmosis

While testing in areas with EDB and other pesticide contamination, nitrate levels greater than the State's standard of 10 mg/L were often discovered. In 1992 the Department began to restore or replace these nitrate-contaminated wells. In cases where a connection to public water system is not cost-effective, POU reverse osmosis (RO) filters are installed, usually under the kitchen sink. These filters have a total dissolved solids (TDS) indicator light to show when the filter is no longer working properly. Over 580 of these filters have been installed to date. All RO filters are exchanged annually.

Ion Exchange

Where nitrate standards are exceeded at a Public Water System and the WSRP's assistance is requested, a POE nitrate filter must be installed. For these systems an ion exchange filter, containing a nitrate removal resin, is installed which is similar in appearance to the carbon filters, although the process is quite different. These filters are sampled quarterly, because they need to be regenerated with a brine solution, to ensure the resin is performing satisfactorily.