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What Happens After You Flush
The Boise watershed includes the South, Middle and North forks of the Boise River, Mores Creek and Foothills
drainages from the lower basin. But if you start at the headwaters of teh Boise River, you're looking at an area
that extends from the base of the Sawtooths to the Oregon state line.
The size of the drainage doesn't guarantee
a healthy supply, especially when most people are unwittingly working against it. Dog droppings left on the ground wash
into the river and are its second largest source of harmful bacteria, and flushing chemicals pollutes wastewater to such an
extreme that it's almost impossible to clean. The West Boise Wastwater Treatment Plan processes nearly 30 million
gallons of wastewater every day, discharging it cleaner than the river it came from.
Here is how it works:
1. Water moves from city sewer pipes to an
influent tank three stories deep.
2. From there it is pumped into a screen room where large, nonbiodegradable solids
and grit are removed.
3. The remaining liquid moves into clarifiers, where it is run through several fine sets
of teeth. Biosolids are removed.
4. Water flows into the aeration basin where oxygen levels are controlled
to stimulate waste-eating microorganisms.
5. Water is run through secondary clarifiers, and the return activated
sludge is cycled back to the aeration basin for the "bugs."
6. The rest of the water moves into ultraviolet
disinfection channels that sterilize harmful bacteria before pumping the water into the Boise River.
7. Surplus
sludge goes to the digester, where it is heated to 98.6 degrees.
8. Methane gas emanates from the heated sludge
and is stored for re-use.
9. Leftover sludge is squeezed in a belt press, and water goes to the influent tank.
10. Biosolids are collected and transported to a city-owned farm that grows feed crops for Idaho farm animals.
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