Homemade Mini Microbulator

I had ordered the KIS aeration compost tea brewer ($290 + $30 shipping), having read the glowing recommendations by Dr. Elaine Ingham and Jeff Lowenfells of Teaming-with fame, but unfortunately something is up with their manufacturing process and they’re on back order until July (or indefinitely?).  I cancelled my order and settled on Mr. Tim J. Wilson’s new and improved Mini Microbulator. Also check out his website, full to the brim with info on brewers, brewing, complete with microscope assays (this one for the mini microbulator).

Here is his Mini Microbulator – love that name! – at work.

This one is also for sale, but I just bought the plans ($7 – thanks Mr. Tim!). I got the Elemental O2 Commercial Air Pump (951 gph) from my local hydroponic store – this cool place, it’s like a candy store! In the end it cost me: $7 for plans, $33.43 for the pump, $38.08 for the fittings and hose (and tax) = $78.51.

Though in his plans Mr. Tim uses a 3/8″ ID (inner dimension) hose (with a 3/8″ barb) I followed the advice he gave in a comment on this video:

Your airlift will run with extreme more efficiency if you use a larger diameter airline. Just eliminate the little brass nipple which screws into the pump and use an airline which goes over the nub on the pump, * score the nub with a hacksaw to create something for the airline to grip * clamp the airline securely,  * use a similar size air input nipple into the base of the airlift. This way you will get full efficiency and higher capacity dissolved oxygen from the bioreactor.

So I used a 1/2″ ID vinyl hose (and a 1/2″ barb) instead. I didn’t score the nub on the pump because it probably voids the warranty. I clamped it tightly and will keep an eye on whether it pops out.  HOWEVER

{IMPORTANT UPDATE 6/9} The pump cannot handle the difference between the intake/output ratio if you eliminate the brass adapter. It becomes MUCH louder and the short-circuit-like noises it makes indicate it’s not working properly. At first I thought it was the pump malfunctioning, but when the second one also did this, the store cleared up the mystery for me (thanks, guys!). So, the brass nipple went back in, and I went back to the hardware store for the 3/8″ ID hose…

The base of the airlift fits very tightly (almost not) into my bucket, but it’s a good thing. It makes it super stable and wedges everything together, which means I don’t have to glue any of the fittings together and will make for more through cleanup after each brew.

The riser sits in the middle of the bucket, which prohibits the formation of that vortex everyone likes (Mr. Tim’s 50 gallon microbulator does create a vortex). From what I could see from my first test runs, a lot of air gets pumped into the water/tea, though. Mr. Tim writes that “the dissolved oxygen (DO2) of a finished batch has been over 7 ppm for us with water TDS at around 75 ppm but as high as 9 ppm DO2.” Elaine Ingham writes (here for  a pdf of the best scientific primer on compost tea ever) that the tea should remain in the aerobic range at all times, that is, above 6 ppm or 70 to 80% dissolved oxygen. At some point I’d love to buy an oxygen probe to do my own tests. After I get my microscope!

But first, I can’t wait to make my first brew {UPDATE: I did!}. But I’ll have to find a good place to locate this operation first. The pump is pretty loud, as well as all the splashing, and as a brew usually take over 24 hours, preferably 36 hours, I’m not sure I can get away with it in the basement under our small, one-story, house…

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  1. Were you able to work out the issue regarding the removal of the brass nipple with Tim (I saw that he asked you to email him)? I’m building the same brewer and thought I may run into the same issue since I’m using the Elemental 571 gph pump which is weaker than what you are using.

  2. Hi Joe, the guys at the hydroponics store told me it’s not good to remove the nipple because its diameter (of the air output) is calibrated to the air intake. It works, but the wear and tear must be higher when not used as designed. The moment I replaced it, the pump stopped making noises. So I am now using it with the nipple.

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