Collier County's North County Regional Water Treatment Plant (NCRWTP) is a combined
nanofiltration (NF)/reverse osmosis (RO) treatment facility, with design production capacity of
20-mgd (12-mgd NF, 8-mgd RO). The RO portion of the NCRWTP treats brackish water from 11
wells in the Lower Hawthorne Aquifer. Since their construction in 1998, 4 of the 11 wells have
experienced increased total dissolved solids (TDS). The chloride concentrations in these four
wells increased from a range of 2,000-3,000 mg/L to 6,000-10,000 mg/L by 2002, rendering
them useless to the existing low pressure RO system.
The production loss from these wells allows the NCRWTP to marginally meet the 11-mgd raw
water required for the RO portion of the treatment system by eliminating available redundancy.
Additional wells are planned for the future to improve the raw water supply capability; however,
the prospect of abandoning four highly productive, permitted, and relatively new wells is not
favorable. Instead, the concept of independently treating the raw water from the high salinity
wells was investigated.
Treating high salinity groundwater using seawater RO (SWRO) technology is a new concept in
Florida. In theory, this scenario presents an ideal application for SWRO technology because of
the high quality of the groundwater with respect to silt density index (SDI) and turbidity and the
history of successful treatment of water from the Lower Hawthorne Aquifer by RO. However, the
absence of past experience with SWRO technology and the potential for unforeseeable
treatment challenges warranted demonstration testing.
The objectives for this RO demonstration study were three-fold:
verify treatability of high salinity Lower Hawthorne groundwater with SWRO technology
and minimal pretreatment (5-micron filtration and scale inhibitor only);
develop energy use, chemical consumption, and cleaning interval data to estimate
operational costs and establish full-scale design criteria; and,
familiarize Collier County operations staff with isobaric energy recovery technology.
This paper discusses the application of the latest seawater technology for the treatment of
highly brackish groundwater in Florida. Included is information on the development of the
demonstration testing protocol, establishment of the most economical design recovery and flux
rates, and the performance of the low energy seawater membranes and isobaric energy
recovery devices. Operational data from the demonstration study is presented, including operating pressures, water quality, and energy usage. This paper serves as a roadmap to other
utilities who are suffering from a reduction in potable water supply due to salt water intrusion
and provides concrete evidence that the latest seawater technology and design concepts
significantly lower the cost of treating high salinity water. Includes tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 380 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 15 |
| Published : | 03/01/2007 |
