Slow sand filter update

Posted on January 27, 2017 by filter_guy

It is now January 27 of 2017. Its been cold this past 6 weeks: below freezing for 42 days with only 5 days where the temperature was in the upper 30s during the daytime. The ground remained frozen the entire 42 days. That’s 42 nights of  below freezing temps here, mostly in the lower 20’s. All of the filters, with the exception of filter 3, and 4,  were frozen solid until 5 days ago. Filter 3 and 4 froze up when I forgot to increase the flow at night. Had I kept the flow up they would not have frozen. Filter 3, and 4 are the ones that have continuous flow 24/7 from the use of a small pump that either recirculates water through them or runs water through them from a surface well. When I am able I will check all the filters out to determine the extent of damage, if any, and i will post it here. Most of the pipes were not glued, so they just pushed apart with no damage, but I will need to check more closely as the weather warms up. This has happened before just about every year and the filters just keep on working. This year the cold spell lasted slightly longer.

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2 Responses to Slow sand filter update

  1. Anthonius Purba says:
    November 27, 2017 at 1:48 am

    Dear Sir,

    I have a question about the sand media specification usage in Slow Sand Filtration. I understand concerning the ES and UC. However the question is: How about the 40% larger grain size remain of d60 and similarly concerning the 10% d10 smaller grain size portion. Is that portions be excluded from the usage in the SSF media, means say the media only consist of larger size than 10% upto smaller size than that 60%.
    Please be kind to answer my confusing. Secondly did the RIVER SANDS had an Sole Agent in Indonesia/Jakarta?
    Regards and Sincerely
    Anthonius Purba

  2. filter_guy says:
    January 4, 2018 at 9:06 am

    The grain size you use in your filter must be determined by the flow rate you need, the turbidity of your input water, and the degree of filtration you need. The idea is to have all grains of sand close to the same size. Finer grains of sand will result in a slower flow, coarser grains of sand will result in a faster flow and less effective filtration. This should be determined in your pilot test (trial run of the first filter design). Do a search on this blog to find my info about grain size. There is a search box near the top on the right hand side of the home page.

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