I was inspired by Ethan's threads about making a Foam Fractionator (FF), and wanted to experiment with another method of removing dissolved organic compounds (DOC's) that is modeled after the Protein Skimmers I have used before on my salt water aquarium.
I had an extra 55 gallon barrel and some extra PVC pipe & fittings. So here is a drawing of what I put together after some trial and error. I'll follow it up with pics and some discussion about the results.
Basically, I made a protein skimmer inside of a barrel, so that water flows down through the 4" pipe into the barrel, in the opposite direction of the air going up the 4" pipe. I narrowed the opening to 3" pipe at the water surface, causing the bubbles to accelerate and push up the 3" PVC pipe.
The 3" pipe is 17" long, giving plenty of "adjustment" room so that water stays in the pipe, but bubbles and foam want to push out the top of the pipe.
In order to prevent the bubbles (which are coated with the DOC's) from landing back in the barrel, I cut a hole in the bottom of a 5 gallon bucket, and used PL Adhesive to attach the bucket to the pipe (a bulkhead or fitting of some sort would be a better option).
Another issue to address was that I didn't want the collection bucket to fill with slime/water and get heavy, so I added a drain down low on the bucket and directed it to a bucket on the ground which is easy to carry off and dump.
The upside down ice cream bucket on top of the 3" pipe is suspended so that it does not actually touch the pipe. It serves to shield the forming bubbles from wind, and to keep little splashes from popping bubbles from flying all over; instead, it all hits the inside of the ice cream bucket, and falls into the collection bucket.
I used a bungee cord to help hold the unit upright inside the barrel.
I did not glue most of the pipe fittings inside the barrel to allow for adjustments. Here's the concept drawing: