Page 19 - SIMPLIFIED WASTEWATER TREATMENT FUNDAMENTALS\ Advanced Activated Sludge P3
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Aeration Contact Time
Winter Season Contact Time Example
In the middle of the winter season, this northern wastewater facility’s wastewater temperatures are
approaching 8 C (46 F). Under these extreme conditions of slow cellular metabolisms, Process Control
dictates a need of at least 6 hours of Contact Time to adsorb enough food before leaving the Aeration
Basin to settle and absorb (or ingest food) within the Secondary Clarifier.
Factors:
Flow 0.8 MGD (combined Influent Flow + RAS Flow) Aeration Basin Volume 430,100 gallons
Detention Time Formula
Volume MG x 24 Hours = Hours Volume 0.4301 MG x 24 Hours = 12.9 Hours
Flow MGD Combined Inf + RAS Flow 0.8 MGD
Under this low flow winter season scenario, the Aeration Basin is easily meeting the 6-hour process target.
