Below is a one sentence description of the Mineralisation Tank (MT) which I use to mineralise aquaponics solids waste, which is collected via filtration within the aquaponics loop.
A 200 Litre plastic blue barrel containing watery solids’ fish waste which is aerated via an air pump… That’s It!
Before upgrading to the 200 Litre barrel, I simply had a 20 Litre bucket with an air stone doing the same.
Every few days or at least once a week, I turn off the aerator and wait for a few hours, then syphon off 20 to 50 Litres off the very top as the solids and a lot of the suspended solids settle, leaving the desired plant-ready food above.
I try to remove the captured solids in a Radial Flow Filter every day when fish are feeding (sometimes I miss a day). This is the solids waste I put into the Mineralisation Tank.
I have pad filters on the output of water delivery into the growbed, and a pre-filter on the sump pump. These filters get cleaned once a week to fortnight. They are cleaned directly above a garden and do not contribute to the solids waste entering the mineralisation tank.
I’ll now take a step back for a quick wider view of things aquaponics related here….
Bacteria in Nitrification & Mineralisation
It’s my understanding that bacteria dominate most Aquaponics nitrification and mineralisation processes.
Fungus in Nitrification & Mineralisation
These guys are also present, however to a lesser extent, to keep things simple, I will not speak of these little fellows in this discussion, and unfairly pass credit to the bacterium :)
Solids Waste In an AP system consists primarily of fish faeces, however uneaten food along with a few other items are included in the solids waste. The desire is for this waste to be mineralised.
Direct ammonia waste from the fish
Fish also produce ammonia waste directly, you cannot see it but there’s plenty of it.
Nitrification of Ammonia
Ammonia is converted to Nitrite by Nitrosomonas bacteria, then Nitrobacter bacteria convert the Nitrite to Nitrate.
Ammonia & Nitrite do not have available nitrogen for plants to uptake and are unsafe for fish at any level. Where Nitrate is very nitrogen available for plants (and safer for fish at low levels)
Mineralisation in reference to Aquaponics
There are 2 types of Mineralisation referred to in Aquaponics.
1. Aerobic Mineralisation is the bacterial (mainly) breakdown of solids waste to smaller and smaller solids, with a resultant of ammonia being the expected outcome. This can, and usually leads on to nitrification of the ammonia within a mineralisation tank (when oxygen is kept available). The end result is usually a Nitrate and Mineral rich mixture (like Iron, Potassium, Calcium, magnesium…), a plant-ready food inoculated with Nitrosomonas & Nitrobacter bacteria for the plant component of the aquaponic system.
2. Anaerobic Mineralisation (widely used in Reticulated Aquaculture Systems, and other including some aquaponics systems). Briefly, the primary uses for these are to break down solids waste and de-nitrify the resultant as much as possible which produces an output of almost nitrogen free water and basic minerals (in most cases basic elements like Iron, Potassium, Calcium, Magnesium…). Most of the nitrogen is dispersed as gas in this process. Low oxygen conditions and anaerobic bacteria are used to achieve this outcome.
Nitrogen fixing bacteria such as Aztobactor, Rhizobium (and others) play a major role in soil plant nitrogen cycles, by taking plant-non-accessible atmospheric nitrogen and converting it to plant accessible nitrogen. Particular types of these bacteria such as Rhizobium are present and function in an aquaponics system, however I have little documentation to the extent that nitrogen fixation takes place in an aquaponcs growbed. For now I have run out to digging time on this one, and should update when I’m comfortable with some future found information.
Mineralisation Tank designs range from basic (like mine) to complex, which may contain screens and baffles, some are In-Line, Off-Line, Off-Line Plumbed manual & semi automated …
I mainly focus on my basic MT here, which is Off-Line due to the fact that it is completely removed from, and out of an Aquaponics Loop.
Aquaponics Loop, without getting complex over the varying configurations out there.
The AP Loop is the reticulation of water around the in-line components of an AP system, for example, a basic outline for an AP Loop might be…
As well giving the plants a growing platform, the flood & drain growbed functions as a bio-filter preforming nitrification, mineralisation (for un-filtered solids, especially suspended). Although many do not wish for mineralisation to occur in the growbed, mineralisation occurs to some extent due to little, some, or lots of suspended solids getting through filtration.
A Growbed can be many things to many different people….
System designs range from little or no solids filtration to high solids filtration. The different designs, pros and cons for these variances are not for this posting to elaborate and speculate on. I would consider my aquaponics system to have only average solids filtration.
So why do I have a MT? The primary reason is to make available for return, the plant-ready nutrients derived from the fish solids waste which are removed from the AP system by filtration, without placing further load on my out of balance single growbed.
If my system does not require nutrients, the lucky pot plants, wicking beds and lastly garden get some instead. As the temperature drops slowly into winter, my Jades will stop feeding, there will be a lag before nitrate production drops as the growbed mineralise and cycles down the unfiltered solids. When the plants start to get hungry, most of the decanted water from the MT will go back into the AP loop.
iAVs principles are not considered in this discussion, this is due to the iAVs having closer conditions & biota to that of soil … Minineralisation, Nitrogen fixing and nitrification all occur in the iAVs sand grow beds, with no need for additional solids filtration.
Some good links
http://organicsoiltechnology.com/nitrogen-cycling-down.html -> Great Read!
Microponics Filtration discussion -> This one sides on... to always filter.
Scenerio: Filter the water from the FT, thru a parabolic 100 micron mesh.
<100 microns goes to a bio-filter before the plants get it.
>100 microns goes to a Aerobic Mineralization Tank. This tank can be added 1 or more teas, ( compost, worm, mushroom, manure, etc. ) Good source of extra income from this process.
Thanks Terry. This would be a marked improvement to the filter wool in plastic pots I currently have at the 3 outlets into the growbed. I cannot properly collect the filter waste and settle for washing it out above the pigeon peas... mind you, the peas quite like the extra food.
I'm keeping a look out for 100 micron mesh, I can imagine the finer stuff you'd get from the mesh would make good fuel for fermentation.
Go to Amazon.com and look up "beyondsupply"
Seller has the best prices for T-316 SS Micron Mesh. Sells from 25 microns or larger.
Plus u will need another SS mesh with holes closer to 1/2" Sq or Rd for the backup screen/
There is a video showing how to make a DIY filter were the solids are flushed to the MT, by the incoming water, when I find it I'll forward it also. So the bio-filter would get the small microns and the MT the larger. BTW a coffee filter is 10-20 microns.
Go to this, Scroll to the bottom of Page 9, Wilson Lennard talks about it.
If you have Craigslist in AU, look up Compost, Worm, teas. the sellers here sell it for $5 gal. and you have to go to them and bring your own containers.
What do you think a gal of AP Poop tea with compost, worm, Kelpmeal, etc tea added would be worth, plus the settled slug can be dried and sold also, here a guy sells 1 lb bags of Free Range chicken manure for $10.
OK found the video https://www.youtube.com/watch?v=yE0jTMEi53M
But his screen has too high of a tilt, 30-40 degrees would filter with a smaller dia. tube for flushing the screen so you won't need the filter socks.