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"Going – Going – Gone!"
You’ve just watched the water go down the drain in the kitchen sink,
or down the hole in the toilet. Where does it
go from there? This is now called "wastewater" and it goes
through special pipes to the wastewater treatment plant.
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"Sticks and Stones… Can break the Pump!"
The first stop on the journey of
wastewater is through a grinder or
bar screen. This is where large pieces of rags, toys, trash, sticks,
dead fish/small animals, money and other debris are removed from the
wastewater. These objects could damage the pumps if this gets into
them!
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"Nitty Gritty"
The next stop on wastewater journey is the Grit Removal Chamber.
This is where sand and gravel settle out in the chamber or tank.
Grit is heavy and abrasive and might scratch and damage the pumps
so they won’t work anymore. This could cause the whole process to
stop! These 'settled' objects and the large objects from before
are all removed and sent to a landfill. |
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"Settle Down In There!"
Now it’s time to get rid of the rest of the settleable solids! After the
grit is removed, the wastewater flows into the primary clarifiers,
big tanks where, what's now called SLUDGE, settles to the bottom and the
scum floats to the top. The wastewater is now in two parts - SLUDGE
and LIQUID.
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"Boy! This Really Bugs Me!"
The liquid still needs some cleaning so it is carried to large tanks
where air is blown into it. A population of tiny microorganisms live in this
tank, where they survive by feeding on the organics in the wastewater. The blowing air sets these
little 'bugs' in action to start chomping away on the rest of the solids in
the water. They literally eat this up! And what’s left is a little
cleaner liquid. This is called "BNR(Biological Nutrient Removal)".
There are also two nutrients removed in this process,
nitrogen and phosphorus. The 'bugs' remove the nitrogen and
chemicals (typically aluminum sulfate) are added to remove the
phosphorous. These nutrients are removed because they promote
algae growth, which reduces the amount of oxygen in the water.
(This would not be good for fish and plants that depend on the
air in water!)
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"Bleached"
Our water now reaches the point where chlorine is added to kill off
any pathogenic (disease-causing) bacteria. This is similar to adding
chlorine to your swimming pools. The amount of chlorine added is
carefully monitored to make sure not too much is added, but if it is,
then some of it will be removed. Too much chlorine can be harmful
to aquatic and wildlife.
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"Down River!"
When the liquid is finally 90% clean of its original organic content,
it is pumped back into a nearby stream. At this point, the water is
actually cleaner than the natural stream water itself!
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"Now, What Happened to the...."
While the water is being cleaned up and returned to the nearby stream,
the sludge is continuing on its journey to its new home. First, the
sludge is dewatered by using a belt filter press, centrifuges, vacuum
filters, or drying beds. Sometimes lime is added
to help with the dewatering process. Now we have 'biosolids', which can
be used to help fertilize landfills. (For more information on Biosolids
Recycling, click here).
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