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Ok, My fish tanks are near finished, i have most of the pieces and parts to complete the solids settler (swirl filter). Now im thinking, its time to work on a de-gassing unit. I have an idea as to how it should work and the type of material it should be built with, but would like to see what other have used.

Part of the waste water treatment plant (At work) uses an AFU (Air flotation unit) to separate the material that is lighter that water. Im thinking this would be similar in design. The AFU has a way of skimming froth off the top of the water, my question is, Will a de-gassing unit in an AP system produce alot of froth and is it necessary to have a froth skimmer?

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With allowing the Rafts to fluctuate from the siphon dumps, definitely make your drains from the raft beds very big or you need to make sure there is plenty of extra room in the raft bed above the normal stand pipe level to handle the fluctuation.  A 2" drain is probably not big enough for more than one small media bed (100 gallons) dumping into a 4x8 raft bed.  I'm getting away with a 2" drain on such a set up but if I had more than one media bed feeding that side raft, I would definitely recommend at least 3" drains if not bigger.  I let the raft beds fluctuate with the sump tank so the actual drain pipe in the raft bed is no where near the surface.  If it was setting the water height in the raft bed and then trying to keep up with the siphon dump, it would fluctuate much more.

Definitely any solids or froth could be very nice fertilizers once stabilized.

UVI would dump it's excess solids from the settlement tanks, net tank etc into a pond and aerate it for a time and then pump the sludge into a dewatering bag so they could re, claim the water and then use the de-watered sludge as soil fertilizer for gardening.

They found that the sludge worked just as well as chemical fertilizer applied at the same nitrogen rates.

Stabilized really just means when it no longer stinks I guess.  Kinda like how to know when compost is stabilized.  Can you seal it in a plastic bag for a time and not be knocked over when you open the bag back up.  (warning, if the bag inflates during the few days you have it sealed up, you might not want to breath when you open it.)

UVI used a polymer for flocculation along with the geofabric of the dewatering bag but they also ran tests using burlap with and without the flocculation and found the burlap worked almost as well as the costly geofabric and without the polymer you lost more of the solids back into the water, but you could still retain over 50% I think and the polymer is costly and not organic.

So.......  What I picked up from that was get some burlap bags and once you have let the gunk sit and aerate for a time. scoop into the burlap and let the water seep back out (tip, if you can collect that water it should be pretty rich too.)  Then use the contents from the bags and rich compost in the garden.

Biggest drawback here is needing to have the space to deal with the solids and the extra steps involved with playing in sludge.  If you enjoy playing in your worm poop, then playing in the fish poop will probably be just fine with you.  However, if you don't enjoy playing in the worm castings, then the fish sludge will probably be even worse and you might want to find ways to avoid these operations.

Well if thinking a little differently. Refering back to the de-gasser, with the channel to remove the froth and foam. My thought is to run a small pipe from my sump pump to the froth channel washing the froth into a bucket. Then using an additional pump with a float switch, pump this nutient rich froth back to the inlet of the growbeds. Im thinking about 5 to 10 gallons a day of froth and the sump water used to flush it.

What im thinking is the rites and rates that aren't used by the plants (the first time through the beds) will be concentrated in the froth and instead of just returning this water to the fish tanks where it will do no good, return it directly to the growbeds where it can build up over time to make the water in the growbeds very nutrient rich. If this works, the water returning to the fish tanks should be much cleaner and better for the fish, and the water in the growbeds should be very good for the plants. What do you think?

While I think the base theory may work.  I have a feeling that the actual result may not be much benefit for the extra equipment, plumbing, and complexity involved.  Now that is just an initial gut feeling and has no basis in any actual testing on my part.  If you have the stuff, space and time to tinker with it, I'd be interested to hear about any testing and results you carry out from it.  However, if the extra effort adding this would take might hinder you getting your aquaponics online, definitely skip it so you can get your aquaponics going in some fashion as I've never seen anything that would indicate that such an addition should be required.

Tony, if you've sized and proportioned your system (bio-filtration to stocking density and to an extent for the purpose of my plants), you shouldn't really have any nitrites to worry about...and from every credible study I've come across (in RAS) unless you're in the many hundreds or thousand + nitrate ppm you shouldn't have too much to worry about.

It's a pretty cool project you're working on and all, real interesting stuff, but I share TC's sentiments as to the necessity of it...especially if you're racing against the clock before winter and all (if that's the case). Now I might be talking out of my ass here, but honestly you're probably good to go with a swirl filter and maybe some fines collection/filter. When spring rolls around you might implement or work on the de-gassing unit before the heat of the summer sets in (for your aforementioned reasons O2, increased biological activity etc)...

Insulation as well as heating air and water might be a good place to invest time, energy and money at this time. Don't get me wrong, I'm personally really interested in seeing your de-gasser up and running, but winter in Ohio is right around the corner and without good heating, your system (bacteria as well as fish) isn't going to be able to support the biological activity that you would need the de-gassing unit for in the first place. Just my 2cents. 

Guys, I'm not planning on putting water in my system until next spring. That way i will have all winter to get it completed. My greenhouse is just a metal frame at this point. I still need to trench the lines from the fish room to the greenhouse, The swirl filter still needs completed, So i have more to do than time to do it before winter.

Cool beans then :)

I wish I had your patience and planning. I usually get a wild idea to expand, grab a thousand fish, and frantically build to stay in front of disaster. Ah well.

I personally stock pretty heavy, and feed pretty heavy, and don't have any froth to worry about. Then again I don't have any reason to run an anaerobic denitrification zone, or degas. The only place I have ever had much foam is in a suspended floc tank, which is pretty interesting, but still not enough to do anything in terms of treating the foam. I look forward to your project as well, keep us posted. 

Tony Gilliam said:

Guys, I'm not planning on putting water in my system until next spring. That way i will have all winter to get it completed. My greenhouse is just a metal frame at this point. I still need to trench the lines from the fish room to the greenhouse, The swirl filter still needs completed, So i have more to do than time to do it before winter.


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