THE VIRGINIAN-PILOT
Copyright (c) 1995, Landmark Communications, Inc.
DATE: Monday, September 11, 1995 TAG: 9509110039
SECTION: LOCAL PAGE: B1 EDITION: FINAL
SOURCE: BY JAMES SCHULTZ, STAFF WRITER
LENGTH: Long : 109 lines
Turn the tap in some Chesapeake neighborhoods, and the water that emerges may seem more brine than beverage. But residents' thirst for clean, fresh water is due to be slaked.
A $72 million water project in the works will upgrade the city's current treatment plant on Battlefield Boulevard. A new building next door will house special equipment and filters to cleanse city water of dissolved salts, minerals and organic substances.
Once complete, by July 1998, city officials say the facility will produce water the equal of the premium bottled variety on store shelves.
``Chesapeake is famous in Hampton Roads for salt in its drinking water,'' said Francis A. Sanders Jr., Chesapeake's water resources administrator. ``Our intent is to take care of high chloride (levels) and to make Chesapeake water taste good.''
Spurring the plant upgrade are federal regulations that will kick in by June 1998, establishing more stringent clean-water standards, particularly for dissolved organic matter. To meet those requirements, officials are opting for a process called reverse osmosis, a young but proven technology that will remove almost every impurity from the more than 8 million gallons of treated Northwest River water that flows daily to residents of Greenbrier, Great Bridge and Deep Creek.
``One of the benefits of reverse osmosis is that you don't have to worry about future regulations,'' said O.J. Morin, a senior desalination specialist in Florida with the engineering firm Black & Veatch. ``It takes just about everything out of the water. In fact, you have to add chemicals back in.''
At the heart of Chesapeake's improved facility will be filters known as membranes. Composed of very thin layers of a specially designed plastic - each layer is less than a 10th the thickness of a human hair - the membranes are wound in a spiral, assuming a cylindrical shape.
Pumps will force water at high pressure, on the order of 500 to 600 pounds per square inch, through the filters and into a collector pipe at the center of each membrane. The pipe, scored with small holes, collects the purified water and channels it for further treatment and disinfection.
Some chemicals will be added back into the cleansed water, to balance acid levels, for instance, and to assist in the removal of small dirt particles as the water travels through pipes. But the only two additions that will directly affect consumers, water administrator Sanders said, are teeth-decay-fighting fluorides and small amounts of bacteria-killing chlorine.
``We're looking at swamp-type water,'' he said. ``It comes from leaves and branches that fall and dissolve into such things as tannic acid. The membrane process is very effective at removing so many things.''
Depending on the water's chemical composition, which is constantly changing due to wind, rain and other factors, traditional treatment techniques also will be used. In addition, the use of conventional equipment will reduce the power required to squeeze water through through the membranes, saving money.
According to Sanders, about 30 percent of the flow entering the plant will end up as wastewater - concentrated brine that will have to be disposed of.
Because the brine contains roughly the same amount of dissolved salts and minerals normally found in the Southern Branch of the Elizabeth River, a system of pipes will funnel the discharge there, at no environmental harm.
``You don't want to put water in worse than the receiving body: in this case, the Elizabeth River,'' he said. ``There will be times when we will be actually improving the river.''
Reverse osmosis is used by Virginia Power's Chesapeake Energy Center near the Gilmerton Bridge. There, a reverse-osmosis unit removes impurities from Chesapeake city water before it is used to power steam turbines.
The resulting product is ultra-pure, saving wear and tear on turbine blades by reducing the buildup of potentially damaging minerals.
On the Outer Banks of North Carolina, tens of thousands of tourists and residents drink desalted water from a brackish supply drawn from 400-feet-deep wells. According to Robert Crutchfield, plant superintendent of the Dare County Desalination Plant in Kill Devil Hills, his facility is presently able to provide up to 3 million gallons of drinking water a day.
``I would have to say our plant's performance has been very good,'' Crutchfield said. ``The membranes have performed well. We still have some original membranes from 1989. And our operating costs have been within expectations.''
A thirsty world is increasingly turning to desalting to provide potable water - an estimated 6 billion gallons a day in 1995. According to figures from the International Desalination Association, some 120 countries used various processes to produce fresh water from either brackish or sea waters.
In the United States, reverse osmosis is the technology of choice, because it can be used relatively easily and inexpensively with brackish water. Desalination of ocean water remains quite expensive and therefore almost nonexistent in this country.
``Wholesale'' production of fresh from sea water has traditionally been pricey - at $6 to $7 per 1,000 gallons, vs. 75 cents for reverse osmosis - because only costly metallic alloys can withstand the corrosive effects of ocean water as it's boiled to steam and then condensed into a purified form.
Parched areas may, however, eventually turn to the oceans for their drinking water. While there is yet no large-scale ocean desalting plant in the United States, new technologies now being tested could change that. But not for a while, says desalting specialist Morin.
``Seawater desalting won't happen here in the United States unless circumstances change: until we have to dig very deep wells or pump in water from a great distance and it will cost more for that than to desalt,'' he said.
``Or until there is no brackish or fresh water left. ILLUSTRATION: HOW TO MAKE WATER FRESH AND CLEAN FOR CHESAPEAKE
Graphic
Research by JIM SCHULTZ;
Graphic by ROBERT D. VOROS/Staff
SOURCE: City of Chesapeake, International Desalination Association
KEYWORDS: DESALINAZATION WATER by CNB