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Too much aeration has the kitchen blender effect similar to what sewage treatment plants use. The stronger the aeration the larger the particles that it keeps in suspension due to stronger water currents. I've have seen water logged, neutrally buoyant leaves moving laterally in ponds with lots of aeration currents.

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Is there a way to bleed off some of the air pressure. Some systems allow you to customize the flow to different stations

For over sized aerators or ones with too many lifts per 24hr, I tell people to just put the compressor on a timer and run it fewer hours per day. Generally two lifts per day is enough to keep the pond bottom oxygenated. Exceptions are with ponds with high biochemical oxygen demand they need more circulations - lifts per day.

Bill, I hate to sound completely ignorant, but what do you mean by "ponds with high biochemical oxygen demand"?

Keith

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I don't know if turning the valves 1/2 way is a good idea.. That will create back pressure in turn shortening your compressors life.. I'd get you a time too run say 8-12 hrs overnight..

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qkat - does your compressor have a pressure gauge. If so what does it read while the system is running? Generally if one diffuser is a little deeper than the other one, I suggest the valve of the deepest diffuser be wide open. Then open the other valve and allow the diffuser to boil as hard as you want. This method utilizes all air and minimizes back pressure.

For operating times - first I need to what is the cfm rating of your compressor??


Biochemical oxygen demand is a measurement of the amount of dissolved oxygen that will be consumed by the respiration and decomposition of organisms and organics in the water column during usually 5 days or some specified time period. Basically aerobic decomposition and respiration or the living organisms or the oxygen (DO) that pond water needs to sustain life. The more eutrophic a pond is the higher the BOD measurement becomes, thus the more DO it needs to keep things alive.

Wikipedia describes it as: amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. The term also refers to a chemical procedure for determining this amount. This is not a precise quantitative test, although it is widely used as an indication of the organic quality of water.[1] The BOD value is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20 °C and is often used as a robust surrogate of the degree of organic pollution of water.

To slow the Air One Plus down simply add a bypass valve off of the manifold and exhaust off some pressure.cfm's. This will allow your amp draw to be less $$ than turning the valves down and creating more back pressure. Additional back pressure on that particular compressor will not shorten the life as with your short tubing runs and depth it is hardly working. Just over sized for what you want to accomplish. Consider running it 24/7 but slower. As Bill mentions every pond has a BOD, It normally increases as a pond ages. The key to aeration is to try to size to the potential maximum BOD and always keep the DO supply over the demand. This can be difficult with bloom crashes, plant/ algae organic matter rapidly decomposing from natural or man made causes.

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I've got a bypass valve on my system that I use to bleed off excess pressure. I need to find a use for it...it kills me to simply listen to it hiss, without putting it to work somewhere.

That, or I need to come up with an air muffler or silencer. The escaping air is louder than the compressor itself.

The pressures of 5 and 8 are telling us that when the system is running with valves partway closed it creates 3 psi back pressure which is not optimum IMO. Try to operate the system so the gauge is 5PSI as Ted suggests, which will help allow the "internal cups" to last longer because they and the motor bearings are operating with slightly less pressure (stress). Every little bit helps IMO.

Ted provides a good way to bleed off excess pressure. I by nature do not like to waste the air, thus I usually suggest the pump be on a timer and boil the pond with full air for about 2 turns then let it rest until the next day. Most relatively new low organic laden northern ponds will not loose the DO on the bottom to get close to anoxic condition in 24 hrs until the next daily run cycle. More southern and warmer ponds I am not experienced with. IMO the stronger churning can more quickly mix the entire pond compared to a slower gentler mixing. I've found from testing that both operating methods can work providing the pond is not hypereutrophic.

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I think it's pretty loud. But, I work in a mechanical field, and like many involved in that line of work, I find the sound of an air leak to be an annoyance of the greatest magnitude. However, It may just be me.

The hissing is annoying to me also. The "extra" air can be plumbed into a container that has an air filter that will act as a muffler to reduce the noise.

If the unit is close to the pond just put a hose on it and put it in 1-2 ft depth.(don't blast it into the bottom)

If you want a reduced number of lifts per day - then take Ted's calculation of 8 lifts and divide it into 24 hrs. Thus it takes 3 hrs for every lift to occur. IMO you could aerate 4 to 6 hrs per day and keep the bottom of the pond oxygenated. When I operate an air system for less than 24/7 then I run the system so I see it running when I get up in the morning or arrive home in the evening so I knew that it ran that day.

Try operating it for a shorter period and see how things look in the pond. Pay special attention to your algae and sediment problems in the beach area. Pay attention to the amount of sediment build ups or depths of the sediment or blackness of the sediment. Although, as you have learned, aeration has little to do with subsurface sediment anoxic blackness. If everything appears the same as for the long run time then you are probably okay with shorter aeration periods.

Note - The only positive way to know if the run time is adequate is to check the oxygen concentrations near the bottom shortly (1-2hrs) before the system restarts. Good DO near the bottom means the previous circulation time was adequate for amount of oxygen consumed near the sediment water interface which generally has the highest oxygen demand in a pond /lake.

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You'll need to measure it top to bottom. Look at the Fish Kill thread by Charlie B. He found a place that rented DO meters. They are pretty expensive for a casual pond owner to buy. This is something that you need accurate repeatable readings. I'd look into renting one, getting the readings with the different run times, making a chart, then returning it. A good meter will cost.......

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=344715#Post344715

O.K. I looked up the company that he rented it from, and did more digging. Here's what I came up with. This is the unit that I use, and here is their rental fees: http://www.fieldenvironmental.com/ysi-55...arch_highlight1

I don't know how it'd work if you can't physically go into one of their stores, as I've never used them, but this seems to be a viable alternative to buying one. This is the first place that I've seen that rents them!

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QK - I would not buy a DO meter for your situation or what you need done. Look into having someone come in and do some measurements if you absolutely need to know the DO near the bottom. Maybe Aqua Doc or a fish farm near you? Here is a cheaper alternative to a DO meter. Get an electronic temperature meter; a lot cheaper than a DO meter. Measure the temperature of the water at the surface and near the bottom. If the temperature is within 3F-4F (maybe5F) of the surface and the bottom, then the bottom usually has enough DO for aerobic bacterial growth. My theory: As the circulation stops the water near the bottom begins to cool. Under many conditions as the bottom water cools the DO also begins to get consumed - gets lower. As the bottom water at 2" above the sediment approaches 5F difference of the surface temp the DO drop ed to below 1-3ppm.
Electronic thermometer example:
http://www.amazon.com/Portable-Finder-Sensor-display-back-lighting/dp/B003OUQ1B0/ref=pd_sim_sbs_e_2

There are a numerous exceptions to this rule depending on pond conditions, but it applies to many ponds such as yours. One of the exceptions is how well and how long the pond was circulated prior to stopping the circulation. Some other exceptions are how clear the water is and what suspended solids are in the water column. Those with DO meters can test this theory and report their results here or in a new thread. The accumulative results will be beneficial to all of those that aerate their pond.

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If you want to calculate your temperature loss at the bottom over a 24 hr or 48 hr period, then measure the temp right after the aerator stops and then again in the same spot and depth near the bottom 24 or 48 hrs later. Remember to keep the aerator off for 48 hrs if you are testing for 48 hr difference. Temperature loss often parallels DO loss.