Meet the team (previously with Ionics Incorporated, but now with Seven Seas Water) involved in designing, building and commissioning the largest desalination plant in the Western Hemisphere.
The Trinidad Water and Sewage Authority (WASA) required an abundance of industrial and potable quality water to supply local industrial off takers and potable water customers. Ionics Incorporated and Hafeez Karamath Engineering Services Limited in Trinidad partnered to form Desalcott (The Desalination Company of Trinidad and Tobago) to build and operate the 36MGD (136,000 m3/d) facility. Phased construction began in June of 2000 and commissioning commenced in March of 2002. Among the leaders who saw this project thru to completion are; Brian Hernon (then Head of Engineering for Ionics responsible for overall system design) Bill Sheahan (lead Project Manager), and Allan Pott (Process Engineer and lead Plant Operations Manger), all current Seven Seas Water employees.
The quality of the feed water source from the Gulf of Paria, located off western Trinidad and approximately 10 miles from the Oronco River near Venezuela, is compromised by the river’s run off. This presents challenges seasonally in regard to very high turbidity (over 100 ppm TSS) and salinity fluctuations. Additionally, the intake is located in a ship turning basin so any activity in the area results in further contamination.
The ocean feed water is pumped from the ship turning basin and the difficult to treat gulf water enters into a robust pretreatment system consisting of flocculation, sedimentation, single-stage media filtration and cartridge filtration.
Once treated, the feed water is sent through a two pass membrane process. The seawater is pressurized by centrifugal pumps and is fed to the heart of the facility, a two pass reverse osmosis (RO) system. The 1st Pass System consists of six seawater reverse osmosis (SWRO) units, followed by the 2nd Pass System, consisting of six brackish water reverse osmosis (BWRO) units.
The 1st Pass System is a two-stage system. The first stage consists of 6 trains, each containing 1,456 seawater membrane elements. The second stage of the system consists of 910 seawater membrane elements. A Calder Pelton energy recovery turbins (ERT) are driven by the Pass one reject stream, which recovers energy and reduces the energy required by the pumps to operate.
The 2nd Pass BWRO treats permeate from the 1st Pass SWRO to produce the final high- quality water requirements. Also a two stage system, each 2nd Pass BWRO is made up of 600 brackish water membrane elements. The product water is delivered and stored in a 10.5 million gallon tank on site. The reject from the second pass system is returned to a clearwell within the facility and reintroduced as feed water to the 1st Pass SWRO.
Each First pass unit has a 208 x 130 7M array and each second pass unit has a 80 x 20 6M array. Both first and second pass membrane units have inter-stage boost pumps. Pass one achieves 55% recovery, pass two 95% recovery. So the final product water can be delivered as potable water to be used by industrial off takers or residential customer, post treatment is required. This includes pH adjustment, remineralization and disinfection.
The material contained in this case study is provided for informational purposes only. The information contained is accurate only as of the date the case study was issued. Seven Seas Water disavows any obligation to update information contained in this case study after the date of issuance.