That's right Stacy. 4000 UK gallons, all running just with the Secoh air pump. I'll copy some specs down here:
The tank (diameter=4.56 m or 15 foot, volume= 18000 liters or 4000 UK gallons) is built with coarrugated, galvanized steel sheets. The base (concrete mixed with Sika polypropylene fibers) was waterproofed with SIKA 107 Top Seal and acrylic paint for swimmingpools. The water circulation and filtration run exclusively through two airlifts of 110 mm or 4.33 inches. They aim to create a circular current whose direction of rotation can be easily changed just moving the airlift's elbows. A Secoh air pump (41 watts) provides air to the airlifts via 20 mm (0.8 inches) flex PVC pipe. A third, external airlift will purge the dirt from the central drain. It will be powered by a second and smaller air pump coupled to a timer.
Very nice idea there! I am curious as to the number and positioning of the bottom drains. Why did you feel the need for three of them, and why are they positioned the way they are? Nothing wrong with it that I see, I am just curious as to your reasoning
Also do you feel as though your biological filtration would be more efficient if you added an aerator to stir the plastic media? Or are you relying on the media to help mechanically filter the water as well as perform nitrification?
Last questions have to do with the height of the airlift returns and the style of air injection... Why did you decide to add an additional 2"+ of lift to them by elevating the elbows so high? You would gain potentially 20% more flow by lowing the outlets so that the center of the 4" elbow is flush with the surface of the water. Also it appears as though you are using a single air barb for injection into the riser tubes. This is creating a large bubble instead of multiple smaller bubbles. Why did you choose this for of injection? Simplicity and cost? I am kind of an "Airlift Nerd" so I like to ask these kinds of questions. If you are interested in some of my airlift systems let me know and I will share a couple videos as well.
I would prefer to fluidize the media myself.
air injection into an airlift needn't be bubbles. The most efficient area for a lift is with what's called plug/bubble flow. That happens when the air exceeds 25% of the volume within the lift. Bubbles will become large enough to reach the sides. Above that point, pipe friction will pull micro-bubbles off that, in turn, will lubricate the sides and lower pipe friction. A single injection point works fine as long as the line and barb don't restrict the flow of air. If the barb isn't large enough, a second one can be added.
Lowering the 90 to the waterline would increase efficiency(and flow) Changing the 90 to a T would allow the air to escape so the water can flow a little easier.
These are just points for edification. The pond is to be proud of! Any time we delve into new processes there will be a long learning curve for us to find out it's idiosyncrasies.
Question... I have a airlift setup and we made my TPRs 4' below the water which is now causing a problem as they do not flow. We tried to run a pipe up to the surface and some of them are now flowing. Would it work to run another airline to each TPR and inject 4' below the waterline to increase the flow out those pipes? Currently it is only getting a good flow rate out of a 4" pipe that is just below the surface. I had to actually put a extension on the airlift of about 12" to get the water to stop flowing out of the airlift tank. I'm thinking this is because of back pressure of the TPRs and inserting a airline on each TPR where it enters the pond will relieve the pressure of the pond weight thereby increasing my flow.
Is there anymore info as to how someone would setup a backwash with a airlift? Could you do a airlift backwash on a S&G filter too?
7,400 gallon airlift pond and bog in the making
I have to agree and disagree at the same time Rich.
In small diameter riser tube airlifts then i agree in that larger bubbles (slug bubble flow) will create more flow than multiple small bubbles. I have tested this myself.
In large diameter riser tube airlifts (pipes larger than 2" in diameter) multiple bubbles become more efficient at moving the water as well as lifting it than slug bubble flow. Again I have tested this and confirmed the results. Lots of small bubbles will always out perform a few large bubbles in large diameter airlifts.
A TPR is a gravity flow device so you must create the excess head in the source leading to the lift. If it's in a tank that's at the pond's level you must make the input to the TPR line by dropping from a 90 attached to the exit line.
Injecting the air low on that added line will create a rise in that line(the air/water mix will raise the apparent surface of that line and allow that excess water to enter the TPR line and force water out to the pond.
I am thinking from your 2nd response that it will work.
Last edited by ellisr63; 01-09-2013 at 08:14 PM.
7,400 gallon airlift pond and bog in the making
You build looks great to me. I like the way you have designed it, and it is impressive that you operate the filtration using so little power. Well done! Thanks for sharing the video with us!