A blog from a wastewater guy about various things

Tuesday, February 28, 2012

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.

Saturday, February 25, 2012

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.

Friday, February 24, 2012

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, February 19, 2012

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!

Saturday, February 18, 2012

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.

Friday, February 17, 2012

SPORTS

I went to a local sports bar for fish dinner Friday night.  In the Toledo area we have a channel, Buckeye Cable Sports Network devoted to localsports of all sorts.  I watched Whitmer and  Toledo Central Catholic play.  I noted that the parochial schools and the non Toledo Public Schools bring  a lot more fans.  At some of the TPS games there arent enough people to start a fight, and when there are fights, its the black girls who are fighting.  My daughter went to Start HS, about 1600 students and sometimes they have fewer fans in the seats for a football game than my old school with less than 400 students.

The boys are much more athletic than in my day, but less disciplined on offense.  They are better conditioined, too, as some teams play full court press for the whole game.

I watched the highlights of the Waite and Start girls BB game.  Girls basketball today looks like the game we played when I was a yoot:  lots of passes and jump shots, and rebounds close to the basket and well below the rim

My daughter Sarah played broomball, a big girls sport here.  She was the league leading scorer and her team, the Start Chaos, were champions her senior year.  Here is a picture of her with Lauren Szyzmanski and Samatha Bauman. Sarah is on the left.  She has her mom's megawatt smile.  as she gets older she looks more like her mom.


here is one from the prom



The other girls are her best friends Ella Rywalski and Meredith Shalda

And here you thought I could only talk about poo.

Monday, February 6, 2012

GRAVITY THICKENER OPERATION

Gravity thickeneers can be a useful and easy to operate piece of equiment.  However, there are many who do not operate it properly.  This includes the engineers who wrotde the chapter on gravity thickening in the soon to be published EPA solids handling manual.  If you do not operat it properly, you will have poor performance and a smelly putrid mess.

Here is what is important:

Gravity thicvkening depends upon compressive settling. that is, you allow a sludge blanet to form so the the weight of the blanket above presses water out of the sludge on the bottom.  The sludge collectors have vertical bars, or pickets on theem to stir the blanket a bit and release watger and gas from the blanket.  If the blanket gets septic, you will have lots of gas and scum poor performance and a big stink.

How to optimize thickener operation
  • Pump lots of thin fresh sludge.  Your primary clarifier should ave a ZERO blanket.  Yes, it should.  This keeps the sludge fresh and promotes fast settling in the thickener.  I taught this co9ncept to PSG at the old New Bedford MA plant and the assistant supt. said that they imrpooved primary clarifier removals by 30%.
  • Your surrface overgflow rate should be 400-800 gpd/sf  sometimes you can go higher
  • Use plenty of dilution water to keep the overflow rate up where it belongs.  dilution water should be secondary or final effluent
  • If you arer thickening primary sludge your solids loading rate can be up to 15 Lbs/day/sf
  • If you are thickening WAS it should be no more than 8 Lbs/day/sf and a rate of 4 Lbs/day/sf is better.  Even lower can be better.
  • Draw sludge out on a regular basis.  Put the underflow pump on a timer.  If you have fancy monitoring equipment, you can have the underflow pump shit off when the density meter says the sludge is thin.
  • Check your blanket and maintain what works best.
  • If you thicken cosettled primary and WAS, treat it as WAS for the purpose of solids loading
That waswn't so difficult, was it?

OPERATOR FOLLIES #5

Many  years ago I was working on a start up when I sent into the laboratory and saw two operators smoking dope under the big air intake in the center of the room.  I said  "Jeez guys, all the places you have here to fuck off and youo choose the lab?  They were good operators, though, all of them.  One of the men liked to have a real good time and one night at a party he had a little too much and kinda dozed off.  While he was not paying attention a woman painted his nails and wrfote "I Love You" on the back of his neck.  His wife was not amused

The Fabulous Thunderbirds have a song for occasions like this, called "Amnesia"  I'll try to fnd it on You Tube.

I found it.  The guitarist is JImmie Vaughn, brother of Stevie Ray





She said I went and took back my ring
I don't remember a doggone thing