Do you know where your water comes from? What is in it? And, where does it go when we are done with it? Water we use in our homes, schools, offices, or any other building goes down the drain. That is only one part of its journey.
The process of cleaning waste water varies from treatment plant to treatment plant, but there are some general steps that most of our water goes through once it goes down the drain. (Remember: water that goes down outside storm drains does NOT get cleaned!)
- Stage 1: Screening
- The big stuff is taken out—large objects would interfere with later processes.
- Stage 2: Primary Treatment
- Water flows into large tanks at a very slow rate so that particles and other pollutants separate from the water—some sink to the bottom and are scraped away, and others float and are skimmed from the surface. The waste that is removed is brought to “digesters” that break them down.
- Stage 3: Secondary Treatment
- During secondary treatment, the much clearer water goes through an environment perfectly cultivated to support microorganisms that digest small waste that do not settle out. This environment is delicate and carefully maintained—certain chemicals and contaminants can harm the microorganisms that work to clean the water, which is one reason why it is important that we keep household hazardous waste, and industrial waste out of the water. Most (98%) of wastewater in the U.S is processed with secondary treatment—some, especially those that provide water for reuse, complete tertiary treatment as well.
- Stage 4: Disinfection
- At the final stage of wastewater treatment, the microorganisms used in secondary treatment and any other bacteria are removed from the water by a small dose of chlorine and/or UV lights. The chlorine used is neutralized before the wastewater, now called “effluent” is returned to a natural water source or recycled.
In some areas wastewater isn’t all returned to rivers. In the Bay Area, purple pipes carry recycled water to public areas to water landscaping and parks—most of the time sprinklers with recycled water advertise carefully that the water should not be consumed. In many countries around the world, and now in some areas in the US, including Orange County and San Diego, reclaimed water is being used for tap water in homes.
Recycling water for use in taps is one solution to water shortages, but questions and concerns (and “ick factor”) of communities limit the spread of this practice. Would you use recycled water in your home?
The USGS Water Science School: http://water.usgs.gov/edu/wwvisit.html
Clean Water Services: Wastewater Treatment Process: https://www.cleanwaterservices.org/AboutUs/WastewaterAndStormwater/TreatmentProcess.aspx
CNN: From toilet to tap: Getting the taste for drinking recycled waste water: http://www.cnn.com/2014/05/01/world/from-toilet-to-tap-water/