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Design Guidelines for Aeration Systems and Blowers

Design Guidelines for Aeration Systems and Blowers

(OP)
HI: I have been involved in several aeration system upgrades over the past few years. We always consult manufacturer's of the Diffusers and grids and manufacturer's of the blowers. Together the two parts make up the aeration system for many wastewater treatment processes. The Diffuser Mfg's provide a layout, a recommended flow and the pressure required at the inlet to the diffuser system. The Blower Mfg takes this number and makes a sizing recommendation for the blower typically based on a single operating point. This process has a few concerns for me and I was wondering if you may have some thoughts, opinions and experiences concerning this:

My problems (they are many, but, I won't go there) are:

- it appears as if this process requires that I delegate some of my design responsibility to some one who may not be a licensed professional and does not participate directly in the liability associated with the work;
- with diffuser design as far as the number/area of membrane varies widely from manufacturer to manufacturer. It appears to be due to the loading assumptions made and sometimes these are not easily found;
- when the blower Mfg uses a single design point to size a blower, there doesn't appear to be a consideration of all the loading scenarios that may be present, nor, does it appear to be able to allow the actual operation point of the blowers to be selected;
- there doesn't appear to be a great deal of cooperation between the Blower Mfg and the Diffuser Mfg.

Have you participated in this process and what are your thoughts about it?

Have you come across a concise publication that provides for guidelines for system design? The whole system not one or the other.

Are there any ASTM or other standards that go into the detail of this pairing of equipment? The typical design standard TR-16 and 10-States appear relatively vague to me.

I'll stop here even though there is a lot more. Thanks for anything you might have to say.

RE: Design Guidelines for Aeration Systems and Blowers

The US EPA Design Manual -Fine Pore Aeration Systems is a great reference text. It is over 25 yrs old now but the principles are still relevant.
However you will need to read it and understand it to tackle some of the issues you have raised above.
Then you will have to apply the knowledge and get involved in specification /design , tendering etc so that you understand what you want and tell people.
Whilst there are many good blower and diffuser engineers out there there are also many who know very little.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

RE: Design Guidelines for Aeration Systems and Blowers

- it appears as if this process requires that I delegate some of my design responsibility to some one who may not be a licensed professional and does not participate directly in the liability associated with the work;

There are some reputable diffuser companies that know how to design the diffuser grids to get the effluent quality that you want. There are others that do not. You can check out their design using biowin. There are shysters out there that just want to make a sale


- with diffuser design as far as the number/area of membrane varies widely from manufacturer to manufacturer. It appears to be due to the loading assumptions made and sometimes these are not easily found;

You as the engineer are supposed to be giving them the initial design loads and the target effluent quality among other things. You should understand the concepts of alpha, sote, membrane flux rates, effective surface area for membranes among other things. You should at least have experience in the different membranes that there are out in the industry and their pros and cons.



- when the blower Mfg uses a single design point to size a blower, there doesn't appear to be a consideration of all the loading scenarios that may be present, nor, does it appear to be able to allow the actual operation point of the blowers to be selected;

A blower is no different from a water pump. Performance of a water pump is based on simple point on the performance curve. It is up to you to check with the blower manufacturer to determine if the blower performance envelope can deliver enough oxygen to meet the varying flow, loading scenarios and temperature scemarios that you will encounter


- there doesn't appear to be a great deal of cooperation between the Blower Mfg and the Diffuser Mfg.

I am not sure why you think there should be. Neither of these companies are responsible for the performance of the other manufacturer's equipment. It is up to you to select the blower and operating point THAT YOU WANT AND YOU ARE CONFIDENT IT WILL PERFORM WITHIN YOUR DESIGN ENVELOPE. It is up to you to select the diffuser design THAT YOU WANT AND YOU ARE CONFIDENT IT WILL PERFORM WITHIN YOUR DESIGN ENVELOPE.. That is what an engineer is for

Have you participated in this process and what are your thoughts about it? Do you have a senior engineer who has done this before guiding you?


Have you come across a concise publication that provides for guidelines for system design? The whole system not one or the other. I do not think anything like this exists. Proper design engineering is all about preparing a worst case/best case design envelope of conditions under which the equipment must perform. For example, what happens if the air temperature is 95 oF or 0 oF....what happens if the wastewater temperature varies from 75 oF to 50 oF....what happens if the alpha I assume is different...what happens if my loading is different...can my equipment cover this in the event it happens? The upper and lower extreme likely conditions are called boundary conditions and if we design for these boundary condtions we call this our design envelope that we expect our equipment will work under. Publications don't go into that detail. Engineers have to think "...what if...". You as an engineer are cobbling all the pieces together to put together a custom solution

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