The biologically treated water moves from the Aeration Tanks into the two Secondary Clarifiers. These tanks look like the Primary Clarifiers and can hold 400,000 gallons each.
You may have been keeping count and noticed that at this point we have contained a total of 2,250,000 gallons, or2 million, two hundred fifty thousand gallons of wastewater! And we're not through the plant yet!
Here, like in the Primary Clarifiers, the water coming from the Aeration Tanks, or what we call Mixed Liquor, is given time to settle to the bottom of the tanks while the clear effluent flows over the top of the tanks. The bottom solids, or Activated Sludge, are pumped back to the beginning of the Aeration Tanks where the organisms resume feeding. Left uncontrolled, the number of organisms would eventually become too numerous, and must periodically be removed. This is accomplished by pumping a small amount of the activated sludge back to the bottom of the Primary Clarifiers for disposal with the Primary Sludge.
At this stage of treatment, most of the requirements for our DEC Permit have been met. However, we have another phase of treatment which may be used as we someday reach our design flow capacity.
The cleaned water flowing over the Secondary Clarifiers must now be lifted to the next level of treatment as we have run out of downhill slope!
We do this by the action of two screw lifts located under the green tarp. Each actually looks like a giant turning screw which carries the water up to the next level and can move 9,800 gallons per minute.