really really DSB

[vayapues]

a neighbor of mine is moving. I have spent the day helping her. She is likely going to have to leave a tank behind that was used to store water from the water softner. It would be perfect for a remote DSB, because it already has an in and an out hole.
My question is, is there a limit to the benefits of a DSB by depth. Does deep, always mean better? It would be about four feet deep, and about 20 inches in diamter. The in and out are both at the top, so that no water would be forced through the sand.
Or should I just go with a five gallon bucket as others have done?
Thanks all.

 

[scopus tang]

Now that is an interesting question. Don't know that I've ever seen anything on the limits of the depth of sandbed, in terms of deepness, (can't really remember because it was never an issue) usually the tank depth limits that. Curious to see what someone like Bang Guy has to say on this one; so I'm just along for the ride.

 

[apos]

Anthony Calfo has talked about stores that use RDSBs made out of 55gal tanks to denitrate 1000gal systems: with depths of up to 2 feet.
I think the basic issue is that a certain depth will allow denitrification to occur. Too shallow, and the water diffused in the sand will still have too much oxygen. After a certain depth, you start to get denitrification (mostly only really significant amounts after 10inches or so). The deeper you go from about 14 to 20inches though, it's more like the longer the DSB can last more than extra denitrification rather than tons more denitrification. And at that point the total surface area really matters much much more than additional depth.
The long and the short of it is that you are going to be spending a heck of a lot extra on sand that you probably don't need (though you can just buy super cheap sand for the bottom area. Surface area is going to be your major limiting factor. All in all, probably not much better than a bucket of similar diameter, but perhaps worth it since you have it on hand ready to go.
But I'd also be a little wary of redidue in the walls of this container: exactly what sort of water softener was being used?

 

[michaeltx]

that would basicaly be a fluidized bed filter which is supposed to be a good thing I am not sure how it would work though. I just set up one on my tank that I bought a few years ago much smaller of course.
a remote DSB wouldnt have an in and out where the water would have to flow through the sand like it does in the softener.
even though both the inlet and outlet are at the top I am sure the water is flowing through the sand or salt previously to soften the water.
Mike

 

[reefkprz]

I think after 2 feet of depth your almost gauranteeing a serious run in with creating true anaerobic zones (oxygen free), if an anaerobic zone is disturbed as anthony calfo said it would be "all hell breaking loose in a closed system". also (this will get a couple peoples heads spinning) after being so deep ceartain nutrients and by products of ceartain deep living bacteria can actually cause re-nitrification as the denitrified gasses pass back up through the layers. if there is an over abundance of hydrogen sulfide gasses deep down bacteria will form that can consume it and cause it to revert to a waste product your trying to eliminate..... isnt science fun.

 

[vayapues]

Thank you. Sounds like it is not worth doing it. I do have the sand available already, but it sounds like I risk too many otehr problems.
Again, thank you.