Last week we replaced the sand in two of the filters in the Rossland Water Treatment Plant. This is a slow sand filter system and the sand hasn’t required refilling since the plant was comissioned over a decade ago.
The method used to place the sand is fast and efficient use of labor, with minimal handling of the sand through the process. With four more filters to go, we just need to wait for the turbidity to clear up from these two, (see the last photo above!).
For more information about Slow Sand Filters, check out Wikipedia.
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Does this mean I’m going to have weird-looking water for while?
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Not at all, the water that is run through these filters is not contributing the to city’s water supply, and won’t until it reaches acceptable quality standards – then we move onto the next two filter bays for new sand!
I this a stinky process? I wonder about all the stuff trapped in a decade and the lack of oxygen.
The filters are drained, backwashed, and the top layer is scraped off regularly, that’s the main reason why the sand needs topping up, that over the years so much has been scraped off bit by bit.
Also it’s not stinky, typically there is a layer on the top called the Schmutzdecke which does contain biological activity, (and hence additional treatment), but the raw water in Rossland is pretty clean, so the Schmutzdecke is pretty thin. This layer does take oxygen from the water as it passes through the filter, that’s how it survives, but there is always a supply of fresh water flowing through the treatment plant cells as well.
Is Schmutzdecke dirt blanket?
Good translation, now you know why we use the German, to hide the true meaning! More information here.