Pond Boss Forums AERATION Systems questions Geothermal pre-cooling of air in the summer?

I'm just in the process of designing my 1.3 acre pond and I'v been looking at differant airation methods. I was looking at a wind powered system, and the manufacture says the air line length between the pump (wind mill) and the difusser (botton of the pond)can be up to 1,000 feet. So this got me wondering.

In my situation, if I put the wind mill on top of my hill adjacent to the pond I could fold allmost all of the supply line in a narrow trench, say about 4' deep. Wouldn't this result in some air temperature reductions via ground heat-transfer befor it is introduced to the bottom of the pond? In southern michigan we get about 10 weeks in the summer where ambient air temperatures are relatively warm even at night.

I'm wondering if anyone else has addressed this potential? It also seems like there might be some water warming effect in the winter which might augment the amount of open water durring freeze over periods? Your thoughts?
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The windmill does not produce enough volume of air to have a noticable temperature reduction affect via ground heat transfer in a 1/3 ac pond. Maybe in a 1/4 -1/3 ac but not a 1.3 ac. IMO you are wasteing your money putting a windmilll in a 1.3 ac pond. Boil will be too small and too infrequent for such a large volume of water. Cost of windmill will be 2x that of a 1/4 hp compressor system equipted with similar diffuser as the windmill.

Per previous discussions we have had here, the amount of air-water interface from the bubbles of an aeration system is very small compared with the amount of air-water interface that happens at the surface of the pond (which of course is enhanced by the aeration circulating the pond). The general consensus was that the temperature of the air going in to the diffuser/air stone has a negligable affect on pond temperature compared with the temperature of the air above the pond.

Give TMK credit. He's thinking just like the rest of us. Pondmeistering is an illness that makes you analyze, and sometimes overanalyze every angle of pond management. Heaven help us all.

Indeed this is not nearly enough aeration for a pond this size. The windmill idea is a wonderfully sustainable concept, unfortunately they are not incredibly effective (especially in large ponds). If you think about it, if the wind is blowing hard enough to spin the blades, then you are probably getting decent aeration on the surface anyways. There may be a slight de-stratifying effect caused by the rising bubbles but from my field experience, air stones do not provide sufficient de-stratification unless you use a large number of them over a large area.

OK it sounds like there are two seperate issues here.

1) First is the wind powered airator. The manufacture says the 60" windmill drives a dubble diaphram air pump that will deliver up to 5 CFM at best wind speed conditions, and will treat up to 5 acres. Is this just hype or what? I thought I was going to OVER kill the 1.3 pond?

2) The second is the potential benifit of geothermal pre-cooling. Lets say I use an electric air pump. Any benifit in atempting the pre-cooling?

Yep.


I have a windmill for aeration on my 0.9 acre pond and I like it, both aesthetically and from a lack-of-electric-bill perspective. IMHO there is no question that windmill aeration is more beneficial than no aeration at all. But I think all the above criticisms of windmill aeration are valid.

How often do "optimum wind condtions" occur? That depends on location both on a large scale (North Dakota, for example, keeps threatening to blow into Minnesota.), a medium scale (what terrain and vegetation/buldings surround your property?), and a small scale (where do you place your windmill?).

With membrance diffusers you will get more efficiency from the available air supply than with an airstone.



IMHO, no.

I'm no aeration expert but another part of the aeration equation (hey that almost rhymed) is the depth of your pond. When I performed all the research that I did related to aerating my pond I found out that it was not enough to say that a particular aeration method produced say 5 cfm. You had to know how much CFM was produced at the required PSI in order to reach the depths required at your pond. If I'm interpreting your pond diagram correctly it looks like your two deepest regions of your pond are 20 feet and 15 feet - that's fairly deep. The formulas that I found suggested that it takes .5 (1/2 of 1) PSI per vertical foot of water. So a 20 foot depth would take 10 PSI. In addition there would be some friction loss from running 1,000 feet of tubing.

I think that you would need to determine where (at what depth and location) to place the diffusers and then determine how much CFM you must have at a given PSI in order to pump 1,000 feet and to the depth that you require.

Or I could be completely wrong which is not only entirely possible but is more likely that not.

Look into using a dual head rocking piston 1/3 hp compressor for your deeper water application. It produces higher psi while maintaining good cfm in deeper waters.

IMO you will not get any noticable affect of geopre thermal cooling with either or any basic aeration method. On paper maybe but not in practical application. You would get more benefit by adding well water to the pond.

Im late to the party on this as have not been able to log on for 3-4 weeks/ Had to start a new signon to get this far (old posts gone too I guess) TMK> you are getting some good information. As far as a windmill producing up to 5 cfm I might question that part. I see the Beckermill advertised as a maximum of up to 5 cfm in the new dual diaphram design. I think the wind speed would have to be close to the cutout speed (perhaps 30-35mph) to max out out whatever the top cfm is. Koender always advertised theirs at 1.5 cfm and I could never get more that 1 cfm out of mine at any speed on a 20 ft tower.CFM should not be of great concern,lifting ability should and it is only partially effected by cfm.Example if a diffuser is rated at 2800 gallon per minute lift at 1 cfm in 12 ft of water and another is also rated at 2800 gpm at the same depth but requires 2 cfm then you might want to consider the more effecient one if it did not have drawbacks such as too small of holes or slits (tough to keep clean)price etc.If you want to lift your water 2-3 times per day then you need to know the lifting ability of the diffuser and size a system accordingly.Size a system for the "future" of your pond as they all have an increased BOD as time matures them. Placement of diffusers, current and future BOD, available water source, fish type and population, overall goals and desires of pond,budget etc etc are but some of the items to ponder. A windmill has a lot of variables. I have my Koender in a 4/10 acre display pond which gets the dissolved oxygen monitored dailey.This pond has a high demand for DO as the fish load is med-heavy and is nutrient ladden from the 38 acres of ag watershed that feeds it, It is also a very old pond 40 plus years and requires a different type of aeration than the windmill can provide to meet my goals for it.Most rotary vane pumps that are of the 10psi family will be running at max pressure in your pond at the provided depths but may work OK, as Bill mentioned a small dual head wob-l piston of some sort might be worth exploring.You are off to a great start by asking these questions so continue to do your research./ Ted

Hi, Ted.

Sorry you had to restart with a new logon. The good news is I checked and your old posts are still available for review (450 of them, reportedly) for those who can use all the good info in them.

OK sounds like the geo-pre conditioning is a busted idea, so ill settle for a shallow trench just to keep the air line out of the mowers.

Today I talked to a person at Morgan Winds,in WI. He reported that the syestem he was marketing "deadheads" at 30psi. That would be zero CFM. He also has no other pressure vs. Flow data. Apparently people are marketing these things w/o really knowing what their capibilities are? He had a lot of pond application stories, but very short on the technical side. His wind mill is 6' dia which sounded incuraging. He was very confidant about 3 CFM at 20' water depth with 15 MPH wind speed.

i have always wanted a wind mill on the farm. I like the look of them. I'll keep looking.

Thanks for all you input on this issue, but im still undesided

TMK

http://s266.photobucket.com/albums/ii254/tmikeltn/?action=view¤t=pondpreperation11-25-07.jpg

Looks like a great project.Consider a windmill that will exhaust "dual" so you can run seperate lines to at least two diffusers. I find that manifolding a windmill with a common line to pondside and then split to flow two directions is very difficult. As the psi lessens from a constant wind the air wants to travel to the path of lessor resistance. So when you set a manifold at one given pressure you may lose the air to the deeper or longest tubing run.I would stay away from a single diffuser set up in any pond over .5 acres as in time you may out grow it.Im not sure if a Beckermill or a Morgan is a dual outlet or not but may be worth checking into.Many years back when Koender was toying with the idea of staying with a single outlet but increasing the output to 3 cfm I suggested to them to just supply a good diffuser with the 1 cfm setup they already had as it would outlift the 7 inch airstone they were supplying by 5X. I dont think they grasp the concept at the time. I dont know what they use today for a diffuser. Keep in mind the diffuser is the backbone of the system.I use my mill for winter aeration only when aeration is needed. It is interesting to switch the windmill to different diffusers to see the difference of the size of the bubbles under the ice. Most airstones we look at are very large pore, most single rubber membranes are the same way if they are used heavily in the waste water industry. Large bubble diffusers usually have an ample supply of air supply but windmills have a small amount so diffuser selection is more critical.

If you are going with a windmill your going with a windmill. However, as stated before by others, the rocker piston style compressor would be more effective. In addition, I agree that your choice in diffuser is probably the most important aspect of an aeration system. Choose one that has a laminar flow with the smallest bubble diameter you can find. Finally, diffuser position is very important in that aeration only occurs from the point of bubble rise. Therefore, it is very important that your diffusers are placed in the very deepest part of the pond even if this means putting all the aeration on one side of the pond.

Well I forgot to mention that the only electricty I have on the farm is a portable generator, and I don't think running it to aerate the pond would be too practle.