How to Backwash Fluidized Sand Filter

[Metasyntactic]

So, I know that, if you lose water flow to a fluidized sand filter you can have the bacteria smother and die as the sand settles. In such a circumstance I've read that it's important to backwash your media.

With pool sand filters they actually change the direction of the water flow, essentially fluidizing what would otherwise be a trickle filter. But with a fluidized sand filter, the media is always fluidized so, would backwashing just mean that you lock down your outlet and flush the tank, pumping any toxins to your waste line instead? I'm looking to build a fluidized sand filter and wanted to make sure I build it appropriately for such a situation. I think it's the term "backwash" that is confusing me because you really aren't backwashing it.

 

[Lasse]

You are right. A fluidized sandfilter is back flushed all the time :) If you will have a power breakdown and no oxygen into the filter - it will turn to an anaerobic filter after some time. If your NO3 level is low - the bacteria can turn to produce hydrogen sulphide. If you have the outlet going down in a well aerated area (read rich in oxygen and skimmer apartment) the hydrogen sulphide will be oxidized very fast (it means it will be non toxic) Best is (IMO) to have something that make the filter not to start automatically or with delayed start. It means that you can have time to clean or redirect the outlet before you start the filter.

Sincerely Lasse