The City of Ft. Lauderdale Peele-Dixie Water Treatment Plant is a 12 MGD (1,893 M<sup>3</sup>/day)
facility with four membrane system trains producing 3 MGD (473 M<sup>3</sup>/day) capacity per train. This
plant required a significant review of the optimal dosing of sulfuric acid in lowering feed pH and
the use of antiscalant to control the precipitation of hardness while maintaining sufficient levels
of alkalinity to meet permeate quality goals and chemical costs. The plant used a low TDS well
water supply from the Biscayne Aquifer ranging from 350 to 500 ppm, feed iron up to 2 ppm,
total hardness up to 270 ppm as CaCO<sub>3</sub>, alkalinity before acidification up 270 ppm as CaCO<sub>3</sub>,
TOC as high as 11 ppm, and color as high as 90 Color Units. The
permeate quality goals of this potable water treatment facility were very stringent and required
extensive pilot testing to develop an optimal spiral wound membrane design configuration using
both RO (reverse osmosis) and NF (nanofilter) membranes. A minimum level of permeate alkalinity was desired to make the
finished water less corrosive in the city's distribution piping.
The system configuration by train is a 53 pressure vessel 1st stage by 24 pressure vessel 2nd
stage pyramidal two-stage array with seven element long pressure vessels. The design
incorporated the use of seven ultra-low pressure reverse osmosis (RO) membrane elements per pressure vessel
in the 1st stage. This is followed by a 2nd stage containing 4 ultra-low pressure RO membrane
elements and then 3 high-flow/low-rejection nanofiltration (NF) membrane elements in the same pressure
vessel.
This unique design, referred to as a Double Hybrid RO/NF design, produced the client's
required stringent permeate water quality at a very low operating pressure of about 100 psi.
Pilot testing was required to develop and confirm a design basis and rejection criteria for each
type of RO and NF membrane employed. The position of each RO and NF membrane in the
system has an impact on the specific water quality that the train can produce. Includes tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 920 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 12 |
| Published : | 11/01/2009 |
