Monday, May 26, 2014

Treatment to Tap: How Your Water Gets To Your Home

 Most people never get an inside look at how their municipal water is treated and cleaned, and certainly after 9/11 water sources and treatment plants became greatly restricted to the public. I paid a visit to Santa Barbara’s Cater Treatment Plant for a firsthand exclusive look at just how cities get their water, how it is processed and secured. This is an inside look that few get to experience. The Cater Treatment Plant is similar to many cities across the U.S., and though every water treatment plant is different, this will give an overview of what goes on behind closed doors. First off this is a “surface water plant,” meaning the water they use is not pumped from an aquifer, it is, as the name implies, surface water: from rain and watershed runoff, and this is not a wastewater treatment plant.

Every city has a water resources division who collect, clean, store and distribute our municipal/tap water. Moving water around seems like a simple process, but it is actually a complicated, highly refined system. To begin with Santa Barbara, like all of Southern California, is a semi-arid climate and though we are populated with trees and the Pacific Ocean gleams in the distance, we are not a water rich area. Cater obtains its surface water from Lake Cachuma over the mountains, located in the Santa Ynez Valley. The water leaves Lake Cachuma through an intake tower which connects to a 6.4 mile-long tunnel underneath the Santa Ynez Mountains, then connects to the South Coast Conduit which conveys water to the Cater plant, all done by gravity flow. Water of course is a finite resource and it costs money to transport and clean water for public consumption, all reflected in your water bill, which is stunningly inexpensive.
Inside the plant and underneath the ground our water flows through color coded pipes
Untreated surface water has a slightly negative charge so a positively charged coagulant chemical (aluminum chlorohydrate) is added which neutralizes the charge. An added polymer helps bind, and adds weight to, the suspended material in the water, so the tendency for water particles to push apart has been reduced, and they now clump together, known as coagulation. The water is put into a flocculation basin (imagine really big paddle mixers turning very slowly) causing additional particle collisions, thereby making any suspended material in the water, algae and silt for example, heavy enough to drop to the bottom. Ozone (activated oxygen in essence) disinfects the raw water at the beginning of the treatment process which helps oxidize dissolved minerals like iron and manganese, and conditions the water for a more efficient treatment process.
Though the water looks calm on the surface, beneath it's being cleaned
Then the water moves into a sedimentation basin where a large squeegee-type device rakes the heavy particles that have dropped to the bottom on the basin towards an auger which removes them to three solid recovery beds where the suspended materials dry naturally using sun and ambient wind. Once fully dry it looks like fine black dirt, and it’s stunning and slightly disturbing to see visually what has been removed from our water. There’s also a filtration system whereby the water percolates through 30 inches of carbon, then a foot of sand. Chlorine is still widely used in many water utilities and Cater adds chlorine at the very end of the treatment process to provide a “disinfectant residual” meaning it helps kill of bacteria as it makes its way through pipes towards your tap.
These three solid recovery beds show the final (R) solids removed from our drinking water

Water samples are routinely collected at the plant and run through multiple panels monitoring for turbidity (the amount of suspended and dissolved particles in the water unseen by the human eye), chlorine and bacteria, among a host of other things. Eventually the clean water is held in a “finished water reservoir,” ready to leave Cater and snake its way through a series of labyrinthine pipes. Cater processes an average of 18-20 million gallons of water per day for the residents of Santa Barbara.

Fences help protect public water supplies
Underneath your feet, regardless of what city you’re in, is a maze of hundreds of miles of pipes. These pipes are monitored constantly because a break in an underground pipe means the possibility of bacteria getting into the water supply. Additionally, pipes do not last forever, but out of sight, out of mind, right? Added to that is that certain soils have corrosive effects on underground pipes over time (this is more common in the Eastern U.S. where pipes are much older, some as many as 100 years old) therefore pipes need to be replaced. Every city has a replacement goal for aging pipes to prevent any issues with our water becoming contaminated, but pipe replacement is a time consuming and costly endeavor. Blacktop needs to be pulled up, roads closed, repairs made, water needs to be rerouted and occasionally shut off, not to mention that residents don’t like to have detours on their way to work. But replacement is necessary. Without it, you might not have the water you expect. And this is one of the reasons that your municipal water division in your city or town is an unsung hero – they monitor, clean and protect the water that comes to your house every single day. So the next time you turn on your tap, you’ll a basic idea of the work and effort it took for that water to effortlessly flow.

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