Hypolimnetic aerator idea - 07/09/10 09:59 PM
I've been thinking about keeping trout in small ponds, and considering aeration systems to allow this in upper-midwestern ponds without seepage or spring inflow.
Andedammen posted a helpful link to hypolimnetic aeration systems (http://www.env.gov.bc.ca/wat/wq/reference/aerationapd22.pdf) designed to aerate water below the thermocline without disrupting the thermocline. System A on page 11 looked simplest to me.
After putting my brain to work, I came up with the idea of modifying system A by pumping cold water from a well into the top. This would raise the level of water in the pipe above the pond's surface level, forcing water out of the bottom of the pipe and the pipe branches below the thermocline. Because the well water would be cold and entering below thermocline, the thermocline would not be disrupted. Well water is normally very low in DO, but the diffusor (diffuser?) would fix this: the well water would be aerated for its entire path down the pipe. (system illustrated below)
The well pump could be rigged to run from a thermostat with a temperature probe located in the pond below thermocline level, so that water below thermocline was kept below 63F or so. The pump would need to be adjusted to not pump so quickly that water spilled out of the top of the pipe. The aerator could be left on regardless of well pumping, as it would just be aerating the sub-thermocline water and causing minimal mixing.
The main engineering challenge I see is in keeping this system vertical and in the proper area of the pond. Flotation devices could be attached around the top and the system kept in place using cables attached to shore, or could be anchored to bottom. The well water hose could be run along one of these cables. The well pump could be run to keep the pond deeper than the system's height.
The pipe could be insulated above the thermocline (maybe foam casing could be put around it, to double as both flotation and insulation), and painted in reflective material for the top few feet to prevent solar heating.
Trout would probably have to be fed using sinking food.
Cecil has mentioned that his trout pond operation requires about $100 of electricity per month during summer for the well, but it has to be operated 24/7. My thinking is that with less mixing of warm and cool water, the well would run less, resulting in significant savings. Actually building the system shouldn't be too expensive as long as a well was already in place. PVC pipe and off-shelf components could be used for everything.
The ideal pond for this setup would probably be small (minimize volume to be cooled), steep (minimize mixing), on a north-facing slope (minimize solar heating), and surrounded by trees (minimize wind mixing of water). A pipe overflow would almost certainly be necessary.
Can anyone see any obvious flaws with this system? I have little experience and look forward to feedback.
(not to scale)
Another possible variation of this system, for ponds with very steep walls, might be to just lay the pipe on the bottom, from below thermocline to the surface, pump cold water into the top, and drop an aeration hose down into the pipe. This would resolve the anchoring issue, but might not work well unless the pump was running constantly.
Andedammen posted a helpful link to hypolimnetic aeration systems (http://www.env.gov.bc.ca/wat/wq/reference/aerationapd22.pdf) designed to aerate water below the thermocline without disrupting the thermocline. System A on page 11 looked simplest to me.
After putting my brain to work, I came up with the idea of modifying system A by pumping cold water from a well into the top. This would raise the level of water in the pipe above the pond's surface level, forcing water out of the bottom of the pipe and the pipe branches below the thermocline. Because the well water would be cold and entering below thermocline, the thermocline would not be disrupted. Well water is normally very low in DO, but the diffusor (diffuser?) would fix this: the well water would be aerated for its entire path down the pipe. (system illustrated below)
The well pump could be rigged to run from a thermostat with a temperature probe located in the pond below thermocline level, so that water below thermocline was kept below 63F or so. The pump would need to be adjusted to not pump so quickly that water spilled out of the top of the pipe. The aerator could be left on regardless of well pumping, as it would just be aerating the sub-thermocline water and causing minimal mixing.
The main engineering challenge I see is in keeping this system vertical and in the proper area of the pond. Flotation devices could be attached around the top and the system kept in place using cables attached to shore, or could be anchored to bottom. The well water hose could be run along one of these cables. The well pump could be run to keep the pond deeper than the system's height.
The pipe could be insulated above the thermocline (maybe foam casing could be put around it, to double as both flotation and insulation), and painted in reflective material for the top few feet to prevent solar heating.
Trout would probably have to be fed using sinking food.
Cecil has mentioned that his trout pond operation requires about $100 of electricity per month during summer for the well, but it has to be operated 24/7. My thinking is that with less mixing of warm and cool water, the well would run less, resulting in significant savings. Actually building the system shouldn't be too expensive as long as a well was already in place. PVC pipe and off-shelf components could be used for everything.
The ideal pond for this setup would probably be small (minimize volume to be cooled), steep (minimize mixing), on a north-facing slope (minimize solar heating), and surrounded by trees (minimize wind mixing of water). A pipe overflow would almost certainly be necessary.
Can anyone see any obvious flaws with this system? I have little experience and look forward to feedback.
(not to scale)
Another possible variation of this system, for ponds with very steep walls, might be to just lay the pipe on the bottom, from below thermocline to the surface, pump cold water into the top, and drop an aeration hose down into the pipe. This would resolve the anchoring issue, but might not work well unless the pump was running constantly.