Archive for November, 2011

Ground to Glass

Filed Under Category Health, Water, Water Contaminant, Water Supply by Annie Barbour

Each morning in many houses besides your own, a daily routine begins. You brush your teeth, shower, flush the toilet, make a family-sized batch of oatmeal and remind your children to brush their teeth too. Though morning routines are not identical, life’s basic necessities and cleanliness norms suggest that “getting ready” always requires one thing: water. When you turn the faucet’s handle, you expect water to readily flow from it. But how does it get there, from start to finish?

As we explained in a previous blog post about the water cycle, initially the water is supplied through precipitation, and is collected as surface water or groundwater in a river, local lake or a well. Water is then pumped from one of these sources to a water treatment plant, for the town’s use. Once it reaches the plant, the water goes through a series of treatment processes, to make it safe to drink and use in your home. A typical water treatment plant includes the following processes: coagulation, sedimentation, filtration, disinfection and storage.

After sediment is removed from the water through coagulation, sedimentation and filtration, the water needs to be disinfected to remove illness-causing pathogens. The Environmental Protection Agency (EPA) sets contamination limits for drinking water according to the Safe Drinking Water Act, which are all based on a minimal, healthy level.  Arsenic, lead, viruses and mercury are just a few of the contaminants regulated by the EPA, and reduced by water treatment plants.

Public water systems disinfect water through one or more processes, including chlorine treatment, ultraviolet radiation (UV), and less common alternatives including ozonation, boiling and pasteurization. Gaseous forms of chlorine treat public water, reducing disease-causing bacteria and organisms, and removes minerals like iron and hydrogen sulfide. After primary disinfection occurs and the water leaves the municipality, some disinfectant remains to continuously keep water safe. Some utilities have switched from free chlorine to chloramines for maintaining a disinfectant residual in the distribution system. The secondary or residual disinfectant can, and often times does, affect the taste and odor of your tap water, though is not harmful. Alternatively, ultraviolet treatment kills contaminants through radiation, and safely improves water quality. This type of process does not affect the taste or odor after the fact, albeit nor does it have a disinfectant residual.

The filtered and disinfected water is stored and then used when it is needed. Tanks, aquifers and water towers, are all types of reservoirs used for water storage.  Water towers typically hold enough of a water supply for one day of the population’s use. Water towers are usually elevated by structure and location, providing sufficient pressure to deliver water to the homes and businesses within the town. After the water volume in the tower is reduced from a day’s use, more water is pumped in at night when usage is minimal from the municipal source.  By the time you awake in the morning, the tower is filled with clean water – ready for you, your family and your town’s use.

What is the initial source of your drinking water? Do you know how it’s treated?