PROCESS CONTROL WITH JUST A FLOWMETER, PART ONE

You all know that I think your samplings ande testngs are inadequate to get an accurate quantification of your mixed liquor inventory, and how much you waste.  I'm sure you are all irritated at my daring to suggest that you do extra work.  So, I put the little gerbil in my head to work and came up with an easier way for you to do process control.  Actually, I thought this up years ago but didn't publish it.  In the interim, Alex Exter, the mad Russian, and others have published papers on it.  Still, I thought it up myself with no help, like Newton and Leibniz with calculus. Here is a simple example.  More complex examples will follow after you digest this one

Lets take aplant laid out like so

Flow 2 MGD
RAS  Flow 1 MGD
Aeration tank volume  1 MG
Clarifier dimensions  70' diameter x 12' swd
Desired MCRT  8 days
Wasting Mixed liquor to primary tank

The aeration tank has one million gallons



like this





If you are wasting mixed liquor, to maintain an 8 day MCRT, you waste 1/8th of 1 million gallons or 125,000 gallons

See, that's easy, no pesky sampling and analysis.  Your flow meter is more accurate than your sampling and analysis.

Next time we will figure out wastime with RAS