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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. In particular, the Long Term 2 Enhanced Surface Water Treatment Rule restricts the use of conventional filtration techniques that fail to adequately control pathogen outbreaks, such as cryptosporidium. 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.
While the demand for clean water grows, many treatment systems are approaching the end of their useful life. At the same time advances in membrane filtration technology are providing systems for water treatment that are more energy efficient, less labor intensive, and occupy smaller footprints. Consequently membranes are increasingly becoming the technology of choice where municipal water infrastructure requires upgrading to meet demand.
James City County is a 144-square mile municipality in the picturesque coastal region of Virginia. Positioned at the head of the Virginia peninsula, between the James and York Rivers, James City County does not seem to be the kind of place to run out of drinking water.
However, 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 percent 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. The JCSA''s water infrastructure currently includes a central water system with 29 well facilities, and nine independent water systems with eight well facilities. This infrastructure currently supplies approximately 4.4 million gallons of water per day to 14,735 water customers.
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. The JCSA uses reverse osmosis to extract salts and other minerals, and thus to make the water potable.
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. Designed and built for easy expansion, the facility is expected to satisfy the area’s water needs until at least 2013 at the current population growth rate.
The Five Forks Groundwater Treatment Facility was designed and engineered by Buchart Horn, Inc. and WATEK Engineering Corp. 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.
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 well head to potable water distribution.
Michael D. Vergakis, Chief Engineer – 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.”
“With our own manufacturing facility and in-house research and development group,” explains Jorg Menningmann, General Manager of Aquious – Water Equipment Technologies, “we are able to engineer filtration materials and systems that exactly match the customer’s application requirements. Expertise in systems design, installation, commissioning, training and technical support services are the cornerstones of our commitment to our customers and our continued success.”