fine bubble aeration in lift station wet well

[andjelko]

Can fine bubble aeration be used successfully (for odor control) in lift station wet wells? I know this method is usually used in WW treatment plants, where considerable settling has already occured. Will fine bubble aeration be cost effective in wet wells, as we are now dealing with RAW sewage? (not somewhat treated, as in WW treatment plants).

 

[gibfrog]

1) Wet Well's for gravity systems do not usually smell, unless there is some problem, such as repumping and splashing septic raw influent or improper pump cycling. Consider eliminating the source, such as replacing the repumping with a gravity collection system or eliminating the splashing by introducing the septic feed below the low water level or analyzing the pumping cycle.

2) Aeration may increase the odor problem. The odor problem may be solved by introducing sludge (if you are near a WWTP) or chlorine. If you use aeration, vent the system or force the waste H2S/air into a charcoal or mulch bed or some other odor absorbing media. (You could just force the waste H2S/air into the odor absorbing media w/o aeration)

3) Odor problems are not uncommon. It has been about 16 years since I dealt with them. (I have a current project with one that we will simply eliminate the repumping by installing a new gravity collection system and combining three lift stations into one.)

I hopes that this helps a bit. Clifford H Laubstein
FL Registered PE 58662

 

I agree with gibfrog, that by aerating the wetwell you're more likely to strip the odors and vent even more sulfides/mercaptans from the station. My utility generally has carbon scrubbers on the vent air to control odors at the station - typically using Calgon's centaur carbon.

The odors are likely due to high turbulence in your wetwell (such as drops from influent pipe or channel into wetwell below), or possibly from the manholes just upstream. Can you raise the operating level to prevent such turbulence?

To minimize corrosion and odors downstream, at many stations we have force main air injection. Where there are downstream air reliefs, we substitute the ability to feed ferrous (or chlorine at one station).

 

[andjelko]

Thank you for your responses, but just to clarify a bit.
The lift station doesn't exist yet, I am just looking into odor control measures for a future 10,000 gpm lift station. Fine bubble aeration is an option I am considering. I am a bit sceptical due to the fact that I am dealing with raw sewage, and there is a chance that the costs of for example maintenance/cleaning will outweigh the benefits (if any) of fine bubble aeration on very raw sewage in this wet well.
Are there any other methods other than FB aeration you suggest, which have been proven to be cost-effective?
where could I find more info on this topic?
thank you!

 

[mmo]

Hi andjelko
I have been working with aereation systems for a long time and I agree with gibfrog and others that aereation will increase smell. take into account that you will introducing almos 80% or a inert gas so it will strip odors rather than eliminate them. In some special cases, pure oxygen has introduced just to oxydize odors but is a very expensive method and I do not have results from this experiment.
Aeration willnot be a real solution. May be think about a small water scrubber or somethig else to clean exit air.
But if what you want is to avoid settlement the trpuboe is different
rgds.

 

[gibfrog]

For more info, please check out the bookstore at

http://www.wef.org

(Water Environmrnt Federation).

Search the manuals of practice, written in conjunction with the ASCE [American Society of Civil Engineers] (free character search "mop&quot. Check out the "Design of Wastewater and Stormwater Pumping Stations MOP Fd-20", "Gravity Sanitary Sewer Design & Construction MOP FD-5" and "Preliminary Treatment for Wastewater Facilities MOP OM-2"

Or search google.com -

http://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=wastewater+odor+control&btnG=Google+Search

Best of Luck...... Clifford H Laubstein
FL Registered PE 58662

 

[wwoper]

I see you may still be looking into, and thought of one more potential problem you will need to consider if you pursue the "fine bubble" - you will encounter problems with grit (and probably screenings) deposition which will foul your fine bubble diffusers! (There is insufficient air to keep suspended!) Where we install fine bubble diffusers, we always install good grit removal upstream to eliminate fouling of the diffusers. Without good grit removal, we're limited to "coarse bubble" to keep better mixed and grit suspended. In addition, unless your wetwell is split into two chambers which can be isolated, you will have considerable hassle shutting down the wetwell so you can occasionally / routinely hose and pump out the grit.