Quote:
Originally Posted by Rob  |
I just listened to TR Live Ep. 9, and have a concerns about the RDSB topic.
If I recall correctly, Bobby indicated that his RDSB bucket is plumbed so the incoming water flows through a pipe to the bottom of the bucket, then percolates up through the sand and exits through a drain pipe above the sand bed. Rob likened this to a sand filter, which to me is different than a traditional
DSB.
From what I have read of
Anthony Calfo's thread(s) on the buffering & denitrifying RDSB Bucket, Calfo prescribes plumbing the bucket so the water flows
across the surface of the sand, coming into the bucket above the sand level and having the drain across from the inlet (also above the sand level). The flow (from what I remember reading) must be brisk enough to prevent
detritus accumulation in the bucket, but not too strong as to disturb the sand.
Now we come to (what sounded like) Rob's concern: The thread continued by readers asking how the water could effectively penetrate (diffuse) through 12-14" of sand. Calfo's answer was that if there were a bit of gasoline at the very bottom of the bucket, would we not expect the gasoline to eventually taint the water at the bucket's surface? By the same principal, water that diffuses deep into the sandbed eventually works its way out. Other readers asked if a shallower (ie.. 6", but longer) tray would be more effective than a bucket, and I believe the answer (in lieu of further research) was anything is better than nothing, as long as
detritus does not accumulate. Perhaps larger, longer beds are prone to settling
detritus because the flow is not as vigorous over larger square area? Apart from the oolitic sand, Calfo's bucket was intended to be very cheap to deploy (standard 5g bucket with 2
curved-wall bulkheads, some tubing and a modest powehead.), and relatively maintenance free.
The one question I have may be pertinent. These RDSB buckets may prove to be very effective, but the system as a whole (based on the bioload and amount of nutrient import) may become reliant on the RDSB. Removing a sole RDSB bucket from a system could have catastrophic results, no? Perhaps having multiple buckets, carefully being phased in and out on staggered schedules is required in order that the system doesn't experience a sudden halt in denitrification should a bucket be removed?
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