slow sand filter forum

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3 Responses to slow sand filter forum

  1. Aaron Crone says:

    I am trying to understand your post on sorting sand using mesh screens. I guess I need a little help understanding how you sort and determine mesh size to get the ideal sand size. My understanding is that your recommendation is .15 mm sand for the filter. Based on my conversion you would only need mesh size 60 and 80.

    .0092 inch(60 mesh) is .2337 mm. – effectively everything larger should remain everything smaller should fall through. The stuff that remains would be too large to use.

    .0055 inch(80 mesh) is .1397 mm. – effectively everything larger should remain everything smaller should fall through. The stuff that falls through would be too small to use.

    Please let me know if I am getting something wrong.

    Thank you for all the information.

    p.s. I was trying to order your ebook but was having difficulty.

  2. admin says:

    The gravel should cover the drainpipes by about 1 inch. .35 mm is about the largest size sand you will want. There are sites that suggest using .35 mm sand. I have had better results with .25 mm effective size sand, but the flow rate is much slower. There are 3 pond filters running here that use .35 mm sand, and they are working, but they are running 24/7.

    If you use .35 mm sand, Be sure to limit the flow rate to about .2 meters per hour. With .35 mm sand size your flow rate will likely start out at more than .3 meters per hour if you have a 6 inch supernatent water depth; unless you put a faucet on the output.

    After the failure of the two filters this past spring, I have found that “roughing” the inside of the container is extremely important if you are using plastic or any kind of container that is smooth on the inside. I would rough it all the way to the bottom. I used 80 grit sand paper. Make sure the etching lines in the “roughing” are random. You don’t want them vertical
    All of the blogs and all but one of the websites we manage have been experiencing technical difficulties for some time now. We are working on this issue. It will take some time to resolve. We are currently looking for a new hosting service.

  3. Bob says:

    Dave …
    This is Bob in Astoria. I sent an email this past week, but have not heard back. Perhaps you could check. Perhaps you don’t!
    I am moving forward with the slow sand filter. I have my roof collection system set up and running. Currently, it is set to collect 330 gallons or so. My first flush capacity is 2 – 15 gallon barrels.
    I do have a few questions.
    I have gleaned info your sites and this is what I am starting with for the filter. Space for 4-6 inches of biofilm at the top. Roughen the inside surface of the barrel that the biofilm will come in contact with. The sand will be one grade, 0.35mm (UC < 2) all the way down to the pea gravel (also a little light gravel?) and the manifold. I am having trouble locating good sand. Any thoughts on a brand and where I could get it? We have Home Depot here. It has play sand and some sort of construction sand. No indication of the size or UC. I could get sand in PDX if it available there. If this is the appropriate forum for slow sand filters and we can post pictures, then I will do so at a later date.
    Thanks …

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