From Cloud to Cup
People use water to cook, clean, and brush their teeth, among other things, but did you ever wonder where that water comes from or how it gets to your sink? The main source of Bristol’s water supply actually falls to earth in the form of rain (or snow, depending on the season). That precipitation falls directly into reservoirs, along with water from streams, which is another type of surface water. The other source of Bristol’s water is ground water that seeps into the reservoir. Ground water consists of underground streams and springs and, also, rain, that soaks into the earth after a storm.
The water filtration center in Bristol, located on Terryville Avenue, is supplied by seven large surface water reservoirs. The water is pumped out of the reservoir into the water filtration center through a pipe, after which it is pumped through a flow splitter box that divides the water between two identical treatment trains, each putting out about six million gallons of water per day. The water filtration center carefully regulates the water as it travels through the various stages of cleansing. The water level in each of the tanks is monitored from the control room where there is a control panel that provides a picture of the system and its status. The control room comes complete with alarms and computers that control data collection (the water level in each tank), logging, display, and programming.
Reservoir water (upon its arrival at the facility) is first sent to the four filtration tanks, two for each train, each with a treatment capacity of three million gallons of water per day. Each filtration tank is layered from top to bottom with the following ingredients: 16.5 inches of anthracite, 9 inches of silica, 4.5 inches of garnet sand, 3 inches of coarse garnet, 2 inches of fine silica gravel, 2inches of medium silica gravel, and 3 inches of coarse silica gravel. This filter traps the larger pieces of dirt as the water is sucked through and then pumped into the next stage of cleansing.
The semi-clean water now enters the rapid mixing chambers (two for each train) through which six million gallons pass per day. A substance called poly aluminum, a whitish, flaky material, is then added. The water is now mechanically stirred in the flocculation basins where the smaller pieces of dirt stick to the poly aluminum. After approximately forty minutes in the mixing tanks, the water in each train is sent into a sedimentation tank (six million gallons per day) where movement is halted. In this still water, the poly aluminum and dirt-clumps settle onto lamella-inclined plates at the bottom of the tank. Valves are then opened; the dirt is sucked out, and the poly aluminum is recycled while the sewage is sent to the sewage treatment plant.
After the sedimentation tanks, the water is now clear and clean. All that is left to do before it is drinkable is to add four chemicals. Chlorine, fluoride, sodium hydroxide, and an ortho phosphate are added to the water which is then pumped through a series of half circles in another basin at the plant so they can mix and even-out in the water. About 9,000 samples of water are taken every year to make sure the parts per million in the water meet health requirements and are not harmful. These additives, among other things, protect your water from bacteria and lead poisoning and make it healthier to drink.
The water, now fit to drink, is pumped through a network of pipes to holding tanks located throughout the city. From here the water travels through more underground pipes to reach your house – and your sink! (There are 278 miles of water main in the City of Bristol.) Finally, the journey from cloud to cup is finished!
Bristol Water Filtration Center. Visitation.
Valentino, Leonard. (Superintendent, Bristol Water Department). Interview.
Water is a very precious commodity. Bristol alone uses about 5.5 million gallons of water a day. So, what happens in the time of a natural disaster, such as a flood or a drought when the regular flow of water is disrupted? Consider the summer drought of 1999. Residents were instructed to use less water, to take shorter showers, and were eventually banned from washing cars and from watering lawns. During the drought, the water in our reservoir was down to almost 56%. Ironically, the total rainfall for the year was 52.65 inches, surpassing the level of each of the previous two years; that proved to be a savior when the drought arrived. Hurricane Floyd officially ended our dry spell when it hit Bristol late in the summer. But, what if it happens again? Currently Bristol is negotiating with New Britain to buy 250,000 gallons of water per day from them. Hopefully, Mother Nature will be kinder and wetter this summer.
Valentino, Leonard. Bristol Water Department. Phone conversation.