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Thread: Rolling Algae Scrubber (RAS),The new method for culturing algae

  1. #11
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    Nope. Probably not for another week or so.

  2. #12
    herring_fish's Avatar
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    This product has indeed been around for around 20 years. I believe that this design was created as a way to get around a patent so that it could be made available for retail sale. Unfortunately, sales never got too high.

    I will do a little rambling so I hope that you don't mind. I think that there have been some good points that have been brought up and I will simply play devil's advocate to spark a little more thought on the subject. I haven't really formed and opinion here. It might be a great experiment. LED's can be expensive but they can be re-applied to a more standard design if it does not work out.
    When I read those papers, the light periods where much less than a second. As Floyd said, many studies used algae beds that were flashed thousands of time per second. This leads me to believe that light photons are process at very very high rates.

    A wheel rotates slowly, relative to the "sub light speed" of a good flasher. The algae may be exposed to light for ...say three seconds. Light saturation happens instantly, for all practical purposes. I don't remember many studies that are run under a much longer flash cycle. I drum might take 1 to 5 second to turn around or much more, depending on the speed. The algae would be lit for maybe one quarter of that time, coming to a peak for and eighth?

    I would guess saturation will happen no matter what speed the drum turns. My first thought was that what you are left with is too much darkness in the cycle.

    On the other hand Floyd might have some part of a very valid point after all because the studies were initiated from questions around the flashing that comes from waves in the sun light concentrating light on the algae. I don't remember the term but wave flashing can have somewhat long "low light" periods. There needs to be more studies on longer photo periods.

    Another, probably bigger, issue with the drum is that the motion of the drum or wheel produces water flow over the algae but that flow is still laminar so the algae can still become packed down or clumped. Algae grows much better in turbulent water motion.

    [<Edited In> It would be hard to do but if you could get the incoming water distributed evenly along the entire drum and running in the opposite direction of rotation. This would help to add turbulence and it might help but....]

    That is why bubbles, flow surge devices, dump buckets, motor driven shifting screens or rocking trays are used. These designs increase the efficiencies per square inch of lighted screen.

    Finally, the earlier point is true that the separate issue of efficiency per cubic foot of scrubber unit space is lower because of the one sided nature of the design.
    Last edited by herring_fish; 08-05-2012 at 09:02 PM.

  3. #13
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    I wish i had the space to just test it. Can some ine just test this?.. lol

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