Best diffuser for aerating wastewater tank with high BOD?

Question

Hi,

 

I recently purchased a rotary vane compressor (GAST AT05 Rotary Vane) and I am trying to figure out what type and how many diffusers I should use with it. Here are the motor specs:

 

1/4HP, 60Hz, 115V,
Phase 1, 1725 RPM, 4.7A, 1.00SF
10 PSI Max. Pressure Continuous Duty
4.8 CFM Open Flow
Marathon Motor
 

We are using it to treat brewery wastewater (high in BOD's). We will most likely encounter some sludge formation on the bottom of our treatment pit. Anything that is clog resistant would be better.

It is about 6 feet deep. We have three chambers in the basin. The one we are using first is 10'x10'. I will know more about flow rates in the coming days. We are brewing our second batch tomorrow. I am assuming we will need to treat 1000 - 5000 gallons?

Thanks for your help.
 

Answer 1

Hello,

The pump has a fairly low output at only 4.8 CFM but since the basin is only 10' x 10' you could get four or more airstones into the tank, with one cfm flow for each diffuser. A small or fine bubble system would be best and with the sludge in the basin you would want something that can be cleaned fairly easily as with any diffuser there will be issues of clogging in such a situation.

Probably the best bet, and less expensive, would be fine bubble stones. You could run 3 to 6 of these airstones with your pump. They can be cleaned with muriatic acid when they start getting fouled up. It's a good cheap option: http://www.thepondreport.com/store/diffusers-airstones/airstones-diffusers

Whatever way you go you should use a 1/2" or 5/8" feeder line from your pump manifold to each diffuser to reduce back pressure although with a shallow tank like that it won't make much of an issue.. If suspended solids are an issue you might need to put the diffuser in a weighted pail so it isn't touching the bottom.

We do have some weighted asssemblies with the same airstones attached to reduce any stirring of sediments but for a low-cost solution just put the airstone into a small plastic pail with a few stones to weigh it down.