How is sewage waste water purified and used?


Some of you might have wondered what indeed happens to the sewage that leaves our homes.

Just read on.

The sewage from tens of thousands of homes passes through the sewers, and reach what are called Sewage Treatment Plants (STPs).

The sewage waste water is usually purified and recycled at sewage treatment plants.

At the sewage treatment plant, you will usually find three stages of purification.

  • The first stage, also called the Primary Treatment stage, is where large solid particles are removed.
  • The Secondary Treatment stage is a critical one. This is where a whole lot of the organic waste is treated, usually through the use of bacteria which consume these and in turn get accumulated as sludge. (This organic sludge can be removed and used generate biogas). At the end of the second stage, most of the stuff that you and I see in water as waste is gone.
  • What are left in the water now are usually micro stuff quite a few of which could be hazardous/toxic but are dissolved in water. The Tertiary Treatment stage thus uses methods such chemical treatment and UV-based purification that get our water rid of toxic stuff as well.

At the end of the tertiary stage, the water is so clean that you can drink it and live happily ever after.

I strongly recommend that you visit the sewage treatment plant nearest to you. If they are welcoming folks out there, you can see all three stages in operation right in front of you. If you are the lucky one, your sewage treatment plant might even offer a sample of the purified water for you to take home!


How is sewage waste water purified and used? - Cleantech Guide

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