A LOGICAL MBR

Membrane bioreactors (MBR) are becoming quite popular these days.  I designed one.  MBRs have the advantage of producing reuse quality effluent  and have a small footprint.  They have 2 BIG disadvantage:

1.  The design to peak flows are usually just 2:1
2.  They have a BIG energy demand because of the scour air needed to keep the membranes clean, and the low alpha of the fine bubble diffusers due to the high MLSS that the manufacturers tout. Additionaly, if you live in the cold weather part of the country, you will need to buy lots of extra membranes because  low temperature adversely affects the membrane flux rate

I will propose a different solutioon:  Put the membranes downstream of the secondary clarifiers. Why?

1.  You only need 1/3 of the membranes compared to an MBR
2.  The requirement for scouring air is much reduced, saving energy
3   The membranes can be bypassed, if necessary
4.  You can still eliminate disinfectioin in some states, as the membranes remove the bacteria.

This makes a lot more sense to me.

YOU CAN'T GO HOME AGAIN

Once you have been a consultant, you can never be an operator again.  You can teach operators, design plants, troubleshoot plants, write books, fill in as superintendent, run performance tests, start up equipment, win awards, but you  will never be considered to be competent to work at a plant again.

OPERATOR FOLLIES #6

A few years ago I was working at a plant and needed an operator for a "teachable moment".  I found an operator watching Oprah Winfrey, and he was very angry with me for pulling him away from his TV show.  Really now, Oprah?  Oprah?  What kind of man are you? You could at least watch ESPN.  I bet he watched the "men are pigs" channel too (lifetime).

The belt press operator had a TV in his cubicle too.

This same plant declined to interview me for an assistant plant manager position.

Unattended operation looks better all the time.

RAS RATES

I have been thinking about how to determine the optimum RAS rate for years.  Here's what I think:

The optimum RAS  rate is the one that maintains the system in equilibrium with a minimal blanket.

What RAS control methods are there?

PROPORTIONAL RAS

The proportional RAS scheme is where you select the RAS rate to be a percentage of the influent flow, and to change the RAS flow with the influent flow.  This is supposed to make sure there is sudffdicient RAS to treat the wastewater as the flow changes.

There are two big problems with this method
1.  It assumes that there ios a big inventory to be returned to the aeration tank at a moments notice. Your mixed liquor belongs in the aeration tank, not the clarifier blanket.
2   It will overload the clarifier at high flow.

RAS SS = CONCENTRATION OF SLUDGE IN THE 30 MINUTE SETTLOMETER (AKA RSC=SSC30)

In this scheme the RAS flow is adjusted to maintain the RAS SS at the same concentration as the solids in the bottom of your 30 minute settleometer.  This means that if you have a higher SVI, your RAS flow will be higher, and if your SVI is lower your RAS flow will be lower.  This temds to work pretty well, as long as you pay attention to the blankets at high RAS flow.

CONSTANT RAS FLOW

In this scheme you set the RAS flow and leave it there

This scheme can work well, although it means that you store some of your MLSS in the clarifier blanket at high flow and then return it at low flow.  Still, this works well as long as you pay attention to the blanket

CONSTANT BLANKET LEVEL

In this scheme, you adjust the RAS flow to maintain a level blanket.

This works well as long as you are willing to measure the blanket level several times a day and to keep a LOW blanket level - 2 ft or less.  a 6-inch blanket is not too low.

SUNDAY PAPERS

This is one of my favorite Joe Jackson songs.  In England all the papers are moe tabloidlike than here., Makes for some intresting reading, especially for people in Portsmouth, who havew been marryinjg cousins for far too long.  I think pop music lost its way in the 90's  I agree with the state ment that the past is a different country, but thats a topic for another day

I'll have a techniczal posting in the nest few days

1,000 PAGEVIEWS

Thank you loyal readers!

THERE GOES THE NEIGHBORHOOD

I went out today tto find that the rear window in my van had beed bashed in with a brick.  It must havew been a good heave, because  found the brick up by the front seats.  Nothing was taken.  It must have been the local yoots. Maybe the ones I challenged when they walked 6 abreast in the middle of the road.  Mayve it's time to move and put the house up for section 8 housing.

One side of my car was keyed too.  I tghink a gated community would be good.  A "vibrant" neighborhood means crime.