People ask me how I can champion iAVs given my strong (some would say vociferous) support for filtration.
At one end, there’s an apparently genuine sense of curiosity while at the other end, there’s more than a hint of accusation in the tone of the question.
My response is that there is no conflict.
Sand has been used as filtration medium since ancient times.
Sand filters fall into five main categories:
- rapid (gravity) sand filters
- rapid (pressure) sand bed filters
- upflow sand filters (including fluidized bed reactors).
- slow sand filters.
- Intermittent sand filters (including reciprocating bio-filters).
Suffice to say, the efficacy of sand as a filtration medium has been demonstrated throughout all of recorded history and likely known (albeit not technically understood) well before the written word.
Today, with the exception of reverse osmosis technologies, sand filtration remains the preferred water filtration technology of choice for technologically-informed Western professionals and third-world peoples alike.
It’s low cost, virtually fail-safe, non-polluting, infinitely recyclable, all-natural, low-energy and pollution-free. It just works – and it always will.
Limited perception is the most likely explanation for the failure of aquaponicists to embrace sand filtration.
For additional information, please refer to our articles, “Sand Versus Gravel as a Biofilter Media“, “Sand Selection Guide“, “Sand BioFilter Construction and Operation, Part 1” and “Part 2“.
-o0o-
Gary, Glad to finally see a response to this question that I’ve been wondering about since you first pointed me here months ago. I’m still curious though because yes your previous work (OUAM) strongly advocated filtration and *removal* of the solids to prevent a number of issues such as clogging the bio-filter, lowering the level of D.O. in the water, increasing the ammonia load, and a few other reasons. So far with iAVs I haven’t seen any reference to removing the solids, but it has definitely been implied (if not out right stated somewhere) that for iAVs solids should be left in the system. Agreed that sand is one of the best filters available (both biological and particulate) but unless you are at some point removing the solid waste there is still an -apparent- conflict with your previous position. I’m not trying to suggest that iAVs should remove solids since my reading about iAVs (and other info about sand as a filtration media) leads me to believe that given the efficiency of sand as a filter, the amount of sand used in iAVs would be capable of handling both the bio and particulate load from the system as well as being able to mineralize the filtered solids. Any inert material left over from mineralization would essentially just be more sand.
Above I mentioned an -apparent- conflict with your previous position. After thinking about it for quite I while I don’t see a conflict since your previous position was that solids *removal* in “standard” AP is necessary BECAUSE “standard” AP doesn’t have (in most cases) the ability to deal with the solids without hurting the system. In the case of iAVs, the filtration is capable so there is no need to *remove* the solids.
Josh….I’m glad we realised your expectations. LOL
You’re right. I was/am a staunch advocate for capture and removal of solids.
When I refer to removal of the solids, I’m talking about removing them from the water column – effectively separating them from the fish – in the fish’ interests. In that regard, iAVS does capture and remove all sedimentary and suspended solids. They are trapped on the surface of the sand. They never make it back to the fish tank in any form that can harm the fish. On the surface of the sand, they are exposed to the open air for the vast majority of every day……and to the soil microbes that mineralise them.
This is very different to, for example, a basic flood and drain system, where the suspended solids are just recirculated….and, because they are in the water, they are taking the oxygen required for their decomposition from that water.
This is all consistent with your (correct) conclusion. The difference between iAVs and the basic flood and drain size is seemingly quite small – it comes down to particle size, right?
Particle size is the difference between the best aquaponics system and all of its vastly inferior mutations.