To make potable water for the Lab’s daily transient and resident population of approximately 3,000 people, water treatment engineers at BNL’s Water Treatment Facility (WTF) handle up to 6 million gallons of “raw” water per day. The water is guided through a finishing process that begins at the WTF. The WTF was built in 1963 to remove iron and manganese from the groundwater and has undergone a series of upgrades over the years, the most recent taking place in 1995-96.
Of the five in-service drinking-water wells, wells 4, 6, and 7 provide high-in-iron source water which must be “finished” before being distributed around site. Wells 10 and 11 pump water that is low in iron, so it does not require treatment. This water is simply chlorinated and the pH is adjusted before it enters the distribution system. Chlorine is added to the potable water system to provide a disinfection agent to prevent the spread of water borne diseases. Chlorination is used in every large municipal system and is probably the most important and efficient sanitary measure of production ever introduced.
BNL’s water that needs additional treatment is aerated to reduce carbon dioxide gas and aid in iron oxidation. Lime is added to raise the pH and soften the water and a polymer is added to aid in flocculation.
Flocculation, or the formation of particle aggregates which settle out of the water as sediment, begins in the retention tank. To help form “floc,” water is sent from the retention tank to a slow-mix tank.
Filtration is performed using a rapid sand filter made up of sand and anthracite coal to remove all particles. Filtered water is stored in the “wet well” before it is pumped into the air-stripping towers, which remove volatile organic compounds (VOCs) from the water being treated.
Up to 250,000 gallons of “finished” water is stored at the clear well before its final chlorination and distribution. High-service pumps send finished water from the Water Treatment Facility to the two water towers on site. The water from the two storage towers is delivered on site at 55 to 70 pounds of pressure per square inch via 45 miles of distribution pipe.