MORE OPERATOR FOLLIES

A nice Ohio WWTP put sludge into the waters of the state (well a ditch anyway) when an operator was told to transfer sludge from one tank to another, and then failed to turn the pump off and overflowed the tank.  Andy Barienbrock is trying to help you out with his minimum staffing, but full automation and unattended operations is looking good

PROCESS CONTROL WITH A FLOWMETER PART 4

In this last part we will look at how to account for sludge blankets that or 2 feet deep and more.

In this example wwe will use the old Lynn Marshall average between MLSS and RAS

But Jim! We don't have any MLSS or RAS data!

Fear not, nimrod, I'll show you how

Lets use the 70' diameter clarifier from above

The blanket depth is 2 ft

The blanket volume is 35 x 35 x 3.14 x 2 x 7.48 = 57,500 gallons

to get the MLSS equivalent volume we take the average of the RAS solids and the MLSS solids

From the above lessons, the RAS equivalent is 3 and the MLSS equivalent is 1.  So

MLSS equivalent = 3+1/2 or 4/2=2

MLSS equiivalent gallons = 57,500 x 2 = 115,000 gallons

Total MLSS = 1,000,000 + 115,000 = 1, 115,000

for an 8 day MCRT  1,115,000/8 139,375 gallons as MLSS or 46,500 gallons as RAS

Pretty neat, huh?

A NEW MUSICAL INTERLUDE

I have been reading one of my favorite blogs,  http://www.fredoneverything.net/. , and thinking about moving to Mexico as No one is hiring me.  And with that in mind, some music from Steve Miller.  I coldn't find a good version by Steve Miller, so her is one from Les Dudek

53 Studebaker going for broke............

PROCESS CONTROL WITH A FLOWMETER, PART 3

Some of you are going to whine and say, "but Jim, you forgot about the clarifier inventory!"  I haven't forgotten.  I am just bringing you along one step at a time, and lots of you never consider the clarifier inventory, or use the OEPA calcualation, which is WRONG ( I hope Andy Barienbrock doesn't read this, or he'll never renew my license: I'm already in trouble for standing up to Dear Leader).  I will show you 2 ways to calculate the clarifier inventory as MLSS gallons.

The first way is to assume that the clarifier inventory is pounds is 25-35% of the aeration tank inventory and then add it to the aeration gallons, like this

Total inventory = aeration tank volume X 1.25 = 1, 250,000 from our earlier examples

For an 8 day MCRT, then 1,250,000 gallons/8 =156,250 gallons of mixed liquor to waste, or for mixed liquor as determined in part 2, 156,250/3 = 52,100 gallons of RAS.

Alternatively, you can measure the blanket volume and calculate an MLSS equivalent inventory, like so

Inf. Flow = 2 MGD
RAS Flow = 1 MGD
Aeration Tank Volume = 1MG
Clarifier Diameter = 70'
Blanket Volume = 1'

If the blanket is 1 ft. deep, I would assume that all the blanket is the same concentration as the RAS.  If it is deeper, you should make a different assumption.  Thats for part 4.

the volume of one foot of blanket is pie are squared x 1 ft. or
35' x 35' x 3.14 x 1ft x 7.48gal/cf = 28,800 gallons
The MLSS equivalent is 3 x 28,800 = 86,300 gallons

Therefore, total MLSS inventory as gallons of MLSS are 1, 086,300

For an 8 day MCRT of MLSS to waste it's, 1,086,300/8 = 135,787 gallons
as RAS it's 135,787/3 = 45,262 gallons

That wasn't so hard, was it?

NOTE: when you waste RAS you should do it with a timer on the pumps so you can waste out during all parts of the day.  RAS concnetration changes during the day and to have an accurate portion, you need to remove some several times during the day,

PROCESS CONTROL WITH A FLOWMETER, PART TWO

In part 1, I showed you how to do process control with and aeration, a flowmeter and wasting mixed liquor.  Now you are going to complain about wasting mixed liquor.  So now I will show yoyu how to do it with RAS

Lets review the conditions

Flow = 2 MGD
RAS Flow + 1 MGD
Aeration tank volume = 1 MGD

The RAS will be more concentrated than the MLSS, so we have to find the concentration factor.

Isn't that east?  No sampling or analysis and no nagging from me to do your sampling right

For the next lesson wil will add the clarifier mixed liquor inventory and not use the lab.

The concentration factor is:  Influent Flow+RAS Flow/RAS Flow
Or 2 MGD + 1 MGD/1 MGD  = 3/1 = 3

By mass balance the RAS is 3 times as concnetrated as the MLSS.
So, the RAS flow needed to maintain an 8 day MCRT is 1 MG/8/3 or 125,000/3 = 41,700 gallons

If you have problems with this call me at 419-367-2749

MERRY CHRISTMAS

Here is a nice little rendition of this song

Merry Christmas

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