In February, I began testing a prototype of a water wheel biological filter (see original post describing wheel here). After about a month and a half of testing, I found that it provided decent biological filtration but that it had mechanical flaws. I’ve since decided to retire the project, at least for the summer season. Here’s the scoop:
My neighbor and I built the wheel from ¼” thick, untreated plywood. While pressure treated or stained wood would have resisted rot and water absorption, I did not want to risk chemicals leaching into the water. We also experimented with some Plexiglas, which proved too difficult to cut as it fractured easily.
The wheel was connected to two screen-covered drums by PVC pipe, the pipe was supported by a wooden dowel, and the dowel was suspended by strings at each end. As you can see in the video on the original post the wheel turned well initially; however, after a few days, the wheel noticeable slowed down, eventually coming to a stop. I found that the dowel bowed due to the weight, creating extra friction, so I replaced the dowel with a metal pipe. Nevertheless, after a while the wheel slowed to a stop, too. The wood had absorbed water which weighed it down and it’s possible that bacteria growth also added to the weight. Interestingly the wood did not warp noticeably, but after the trial period, it was covered in little black dots of mold – probably not good for water or our air quality.
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| Black mold growing on water wheel paddles (left) and screen drum (right) |
Meanwhile, I was designing my flood and drain and deep flow technique (DFT) systems* for the outdoor season this summer. The DFT would use the water wheel as its biofilter*. During my research, I learned...
