Florida Keys Aqueduct Authority (FKAA) owns, maintains and operates two seawater reverse osmosis (SWRO) facilities to produce potable water in the event of emergency or disruption to the transmission pipeline that coveys the primary ground water source serving the Keys island chain from Florida City on the mainland. A 2 million gallon per day (MGD) SWRO facility is located on Stock Island near Key West and a 1 MGD facility is located on the island of Marathon in the middle keys. The facilities originally date back to the mid 1960’s with a major retrofit performed in the early 1980’s. In the late 1990’s the plants were in severe disrepair from the demanding environment and corrosive materials of construction.
Harn R/O Systems, Inc. became involved in 1997 and has performed staged rehabilitation work on these facilities that has allowed them to continue reliable operation with an economical approach. The initial work consisted of design, fabrication and installation of new fiberglass RO permeator support frames to replace the rusted-out steel frames that supported the existing DuPont Hollow Fiber Permeators, replacing the carbon steel lap joint backup flanges and permeator connections on the high pressure feed manifolds and concentrate manifolds.
The second phase was the replacement of the original Dupont Permeators with Toyobo Permeators that were specially designed by Toyobo with Harn’s assistance to match the Dupont dimensions. The third phase was the replacement of all of the high pressure 316 SS piping manifolds and valves with AL6XN super stainless steel manifolds and SMO254 valves for the Stock Island trains. The piping design by Harn used the same dimensions for all four RO trains even though each RO train’s existing piping was of varying dimensions. The fourth phase was developing and installing Teflon lined braided PVDF plastic high-pressure feed and concentrate hoses to replace the 304 braided Teflon hoses. The fifth phase was the replacement of high-pressure valves and modification of the existing 316 SS piping manifolds with electropolishing for the Marathon trains. The last phase to date was designing fabricating and installing sample panels for each RO train that allows the monitoring of all of the individual process streams at one location. As funds become available additional improvements will be made to enhance the operation and maintenance of the systems.
Harn’s extensive membrane treatment knowledge and experience with retrofitting existing systems allowed the facilities to be incrementally upgraded in a cohesive and phased approach as the funding became available. Each phase leveraged the previous improvements performed in an economical way using high-quality, low-corrosion materials and components that decreased the operational and maintenance costs of the facility and extended the useful life.
Stock Island RO Train with AL6XN piping, SMO254 valves and braided