Felix Wang and Keith Scott, CH2M HILL, UAE
The Sharjah Electricity and Water Authority, in the rapidly developing United Arab Emirates, is responsible for providing reliable and affordable electricity and water to the Emirate of Sharjah.
As water demand increases, the Authority is turning to seawater reverse osmosis (SWRO) membrane desalination to diversify and augment its potable water supplies. Instead of using heat to release fresh water, the SWRO desalination process employs membrane separation, which significantly reduces energy use.
“The Emirate of Sharjah needs additional water supplies,” says CH2M HILL’s Felix Wang who served as commissioning manager and process engineer. “Salty water comes from the taps in some areas, such as Khor Fakkan. The new desalination plants will serve a critical need in the existing distribution network. It feels great to know that we are doing good work for the people of Sharjah.”
CH2M HILL partnered with the Sharjah Electricity and Water Authority to provide design, construction, and commissioning services for the authority’s first foray into SWRO desalination. The Layyah and Khor Fakkan SWRO desalination plants began exporting desalinated water in October, and for the third plant in Kalba, ME&I construction works started the end February.
Commissioning of the plant will take place August / September. The plant is expected to be handed over to SEWA by the end of November 2009.
Delivering the goods
The three plants were delivered as engineer-procure-construct (EPC) contracts, with CH2M HILL undertaking single-source responsibility for delivering the facilities.
The plants will provide more than 60 000 m3 per day of high-quality desalinated water to the people of Sharjah. Though thermal desalination has traditionally been used in the Middle East, especially in the Arabian Gulf, CH2M HILL was able to lower capital and operating costs by using the new desalination technologies.
The plants CH2M HILL delivered not only provide potable water to the Sharjah people, but also use much less energy than a traditional SWRO facility, making these projects particularly important to the region.
The environments and source waters of the three plant sites differ dramatically, each presenting unique design and engineering challenges. The Layyah SWRO desalination plant lies on the Persian Gulf, about 15 km northeast of Dubai. The Gulf is protected from the open sea and has salinity levels among the highest in the world for seawater bodies.
In recent years, the Layyah site has also experienced high suspended solids along the coastline from the intensive land reclamation works of nearby projects such as Palm Islands, which presented CH2M HILL with additional design considerations for treatment strategy.
The Khor Fakkan and Kalba SWRO desalination plants are located on the opposite side of the Oman Peninsula on the east coast of the UAE, facing the Persian Sea.
An array of advanced desalination technologies was selected at each plant to best address the site-specific challenges presented by their unique locations. The Layyah and Khor Fakkan sites use dual-stage media filters for treatment of the raw seawater prior to reaching the high-pressure SWRO system.
The Layyah site incorporates a dissolved air floatation system before the seawater reaches media filters for enhanced removal of particulates and better protection against accidental oil spills and seasonal algae blooms.
Instead of conventional media filtration, the Kalba desalination plant will use high-performance ultrafiltration membranes, specifically designed for SWRO pretreatment applications. The Kalba plant will be part of the small but rapidly growing number of seawater desalination plants that use advanced low-pressure membrane technology.
All three plants incorporate the highest efficiency energy recovery devices available on the market. These innovative technologies result in the production of desalinated seawater at lower capital and operating costs than conventional systems.
Pilot-testing was conducted at the Layyah SWRO plant for 1 year to design and optimize the operational parameters for the future full-scale facility.
One of the objectives of the pilot testing was to compare the performance of a conventional 8-inch SWRO system, which is the current industry standard, with a large-diameter 16-inch SWRO system. Pilot-testing was also conducted at the Kalba site to establish the design criteria and cleaning regimes at the site-specific source water.
“As the Layyah and Khor Fakkan desalination plants were installed and commissioned simultaneously, we were in the unique position to capitalize on the economies of scale for sharing our lessons learned, equipment sourcing, commissioning procedures, and process optimization among the two plants,” Wang said. “We will now transfer this gained knowledge to expedite the delivery of the third desalination plant at Kalba.”
CH2M HILL’s Keith Scott, programme manager and a seasoned veteran of design-build desalination projects, is responsible for the concurrent delivery of the three desalination plants.
The schedule called for the plants to be constructed and commissioned within six months of each other, with the 30-day plant proving periods to be completed for all three plants by fourth quarter 2009.
“We were able to successfully deliver these EPC projects by staffing lean, skilled, and efficient delivery teams at each site during final installation and commissioning works, and maintaining tight QA/QC control of the work of CH2M HILL and our subcontractors,” Scott said.
Working conditions at the peak of the desert summer often exceeded 45 C with 50 per cent humidity.
“The constant awareness of health, safety, and the environment by our staff,” Scott said, “many of whom are new hires to CH2M HILL, was paramount to the successful delivery of these projects.”
“At the conclusion of these projects,” Scott added, “the team can look to each other and be extremely proud of what we have accomplished together: single-source EPC delivery of three desalination plants to the water-starved Emirate of Sharjah that will serve as showcase facilities for [the authority] and CH2M HILL.”