Aging facilities, increasingly strict regulations and growing communities are resulting in the need for significant investment in new drinking water infrastructure. As these demands place increasing strain on the capacity of existing treatment systems, many municipalities are turning to membrane filtration to treat their sources of surface and ground water.
Government regulations aiming to ensure the safety and quality of public water supply are significant drivers in the growth of membrane filtration for treating municipal drinking water. Compared to conventional water treatment, where the quality of the treated water varies with feed water quality, membrane filtration (which includes ultrafiltration (UF) and reverse osmosis (RO)) is capable of yielding water of consistently high quality regardless of source variability.
Coastal community meets demands
James City County is a 144-square mile municipality in the picturesque coastal region of Virginia. Like many desirable locations on the east coast of the U.S., the population of James City County is currently rapidly growing - by well over 33% from 1990 to 1999. The consequent increase in demand for drinking water has resulted in the James City Service Authority (JCSA) increasing its groundwater withdrawals from 600 million gallons per year to over 1 billion. By 2010, the JCSA expects the population to grow another 40 percent, with a commensurate need for additional potable water.
To meet its long-term forecasted water demand, the JCSA is augmenting its existing fresh ground water resources with saline groundwater, employing reverse osmosis (RO) desalination systems provided by Aquious – Water Equipment Technologies, the advanced membrane separation unit of ITT Industries. The effort to increase the supply of water is taking place at the JCSA's Five Forks Water Treatment Facility. This facility consists of five on-site wells drawing brackish groundwater from the Middle and Lower Potomac Aquifers.
RO desalination systems provide water treatment
The Five Forks Water Treatment Facility provides nearly two million gallons a day (2.0 MGD) of potable water. The new membrane based system which produces this water comprises of four RO modules or "trains", each capable of producing up to one million gallons per day (MGD) for a total of 4.0 MGD. Two trains are fully piped and operating, while the other two are available for plant expansion. County officials decided to purchase all four trains immediately, so they would be assured of having identical equipment when the projected Phase II of the Five Forks project doubles plant capacity around 2010. Commissioned in April of this year, the output of the plant is blended with water from other sources so that the facility is able to provide James City County residents and businesses with a total of 2.5 MGD.
During the desalination process, the brackish well water is forced under high pressure through a semi-permeable reverse-osmosis membrane, which retains salt and minerals. From every gallon drawn from the wells, the system yields 0.8 gallon of potable water. The remaining 0.2-gallon of concentrate is then discharged into the James River via a 12-inch underground pipeline. The concentrate discharge is permitted and monitored for compliance by the Virginia Department of Environmental Quality and does not adversely affect the quality of water in the James River.
Package systems provide solution
In addition to the RO units, Aquious also provided the variable frequency drives for the submersible well pumps, and a pilot unit to be used for the testing of different membranes and pre-treatment and post-treatment chemicals. Aquious also supplied the instrumentation, controls and computer-programming services for the plant wide SCADA system, from wellhead to potable water distribution.
Michael D. Vergakis, chief engineer of water for the JCSA said the county is pleased with the design and performance of the equipment supplied by Aquious. "Although we have only been running the plant a short time, and we are still working through start-up and completing punch-list items," he comments, "the plant is running every bit as well as we had hoped it would run. JCSA is looking forward to a long-term relationship with Aquious for support of the existing plant, as well as the Phase II Expansion. In fact, we are exploring options for moving forward ahead of schedule on the expansion."
