Backyard Aquaponics
A place to discuss aquaponics

So my new grow bed is almost online (just needs a truckload of lava rock media), but bio-load isn't high enough to make it urgent. However i'm running into macro nutrient deficiencies, I think. So I'd like to move on to the next project: solids filtration. I have a plan in my head, which I'm looking for feedback on. Details follow...

My overall idea is to purchase a cone-bottom induction tank between 30 and 60 gallons, and set it up a radial flow filter. At the bottom of the cone bottom tank I would like to install an electrically operated "normally-closed" solenoid valve connected to a relay. The water would flow into a mineralization tank, likely a 55-gallon plastic barrel sitting on it's side. As water/solids from the filter flow into the MT, the displaced water would exit from the other end of the MT and flow back into the system.

The solenoid would be opened by the relay for some short duration, like 5-10 seconds, every 2-12 hours. Using a small solenoid valve and plumbing size, like 1/2" or 3/8" would increase the velocity of water, which should help mobilize the solids that have settled in the conical bottom of the RFF.

The purged solids would dump into the MT, and a weir or something similar placed around the inlet would slow the water down and prevent the flow from disturbing settled solids. Displaced water would exit from the top of the water column via a standpipe or a port on the side of the container. This should ensure only clean water leaves the MT. This clean, but hopefully nutrient-rich water would flow back into the rest of the system.

The idea here is to have a fast turnaround on nutrients that are released by solids breakdown, as well as flushing new oxygenated water into the MT to assist with the breakdown process. The solenoid valve and relay makes the whole thing maintenance-free, I hope.

I'm looking for tips/advice/concerns on this plan. Thanks!

Actually, you want a larger solenoid valve is you want the water to move faster across the bottom of the filter to shift the fish poo. With fish anything other than "small" size, a 3/8 pipe would probably clog up.
Even if it wasn't clogged, it still wouldn't be a faster flow, as there is too much friction with such a small pipe.
I'm still looking for a good cone bottomed container (but am reluctant to attempt to mold my existing filter drum in case it fails - I don't have a spare to work on ATM), but I have a dual timer, with on/off programmable from 1s to 30 hours which is ideal, and will be using 25mm poly on the drain. 5 sec every 2 hours should work well.

In all honesty with a small system like yours I see no reason to use additional filtration. Unless your adding a DWC in the future. Even then Id just polish the water after the media bed into the DWC.

What your describing can all be done within the media bed. Job done.

I agree with charlie, its a very small system for what your describing. but i also say "go for it" just for the fun of it all. i would make it a constant but low flow through system OR replace the solenoid valve with a float valve.

just be sure to check back with us and let us know how it works out.

I guess I'll get the new grow bed fully up and running and integrated before doing anything else.

One concern I have with flood & drain beds is that the rapid draining of water actually pulls some settled solids back into the water. I recently re-plumbed my F&D auto-siphon stuff and there was a lot of scum and solids buildup inside the pipework.

The new grow bed I'll be bringing online is an 8ft long media bed that will operate as constant flow/constant flood. The constant flow should allow solids that settle into the GB to stay there. There will be 144 gallons (9" x 42" x 88") of wet lava rock (scoria) in the bed

and that raises an issue in asking technical questions in isolation.. responders should not have to remember your system or go looking for it..

My only thoughts are, and if this is a tiny system, then would a water cooler bottle not do the job..
and.. what is the need for purging so often... surely it does not hurt much for the solids to sit for a day or two.



I must say that I am unsure of what is happening here..
It is sounding like the the solids collect in one tank and enter another called a Mineralisation tank, and clear/clean water overflows back to the system..

I have not heard of a MT with clear water, and so it sounds like you want to collect solids from a RFF and then transfer it to another device and let it sit there.. so why not let it sit in the RFF..
All you will end up with is anaerobic sludge in the MT

What I am getting at is that mineralisation need a deal of AIR to get it working and that disturbance makes a mess, so there will be NO clear water -- EVER..

I can't help thinking you need to have an off-line MT and occasionally, feed it from the RFF, and then decide how you want to use the MT-Product.. ie. occasionally turn off and let it settle and remove the clearer fluid to the ST and then continue the process..
..
.

I like things to be automatic. More specifically, I enjoy the engineering challenge of automating things...

For the rest of this thread lets assume I'm going ahead with building this thing:

I still have to do some research in anaerobic vs aerobic digestion of solids. At this point I am leaning towards aerobic digestion, in which case I would use an air pump to agitate the water in the mineralization tank and turn off the aeration prior to dumping more water and solids into the tank from the RFF.

The overall process would work like this:

1. Solids continuously pumped from FT enter the RFF.
2. Solids are extracted from the water and deposited in the bottom of the RFF.
3. On a schedule, a valve is opened electronically for several seconds that permits several gallons of water from the RFF to rush out, carrying the extracted solids.
4a. Several hours prior to #3, aeration is turned off to the mineralization tank (MT). During this "quiet time", solids in the MT settle to the bottom.
4b. The water and solids from the RFF flow into the MT.
4c. Water entering the tank is prevented from stirring up settled solids via baffle or weir of some type.
5. The addition of new water to the MT raises the level and causes an equal amount of water to overflow from the other end of the tank. This water is relatively clean due to the prior "quiet time".
6. The water which overflows out would hopefully contain a significant concentration of nutrients digested by the aerobic processes in the MT.
7. Overflowed water re-enters the main AP system.

Joel did something similar in their commercial trials.

Wouldent anaerobic work better in this case?

Great idea I just walked outside to see if I can mock something together. Anaerobic would be ideal because you don't have to add air and stir up the tank but also benefiting from anaerobic bacteria that hopefully isn't anywhere else in the system. The small doses of un oxygenated water back into system will mix quickly.


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I suppose anaerobic vs aerobic depends on whether you want to extract nitrates from the waste, or whether you want to extract trace minerals/elements?

I know, old thread but...

If you are seeing MACRO nutrient deficiencies, then removing solids to a mineralization tank isn't going to fix that problem any quicker than letting your system fully cycle up will.

If you are already simply removing solids and disposing of them or using them outside your system, then yes adding a mineralization step into your system will increase the amount of nutrients in your system but it takes time to fully mineralize solids (like 4-6 weeks.)

I believe Rob Torcellini has come up with a semi automatic settling/mineralization tank design. For the scale of your set up, looking up his Youtube videos on his mineralization tank set up might be worth while.

Definitely thinking of doing this myself
The normal process will be FT-RFF-NTF-FRC-GB

( I am using gravity drain pressure from FT to run the NFT so I can not have the GB first unfortunately )

planing on using 50mm solenoid to remove solid build up in the RFF
with a bit of arduino coding it could be a simple daily~weekly task
FT-RFF-MT-GB


How ever after watching the "Rob Torcellini" video maybe I could also try and do it via gravity feed

The average inexpensive irrigation solenoid WON'T operate with less than about 6 psi of differential pressure. AND it will get all clogged up with the gunk since they are designed for clean water operation.
Most solenoid valves I've seen that will handle operating with no differential pressure constraints cost hundreds of dollars in which case you are probably better off buying one of those swimming pool valves that can be operated with the 24 VAC motorized actuators. If you are into electronics you can create a controller for one of those. I did it with a picaxe M8 chip a DPDT relay years ago.

However, you will need more than just a RFF before you NFT. You will need some sort of fines filter as well or the plant roots will be acting as the fines filter which might seem ok for the first several weeks but before lettuce even finishes you are likely to have a gunk build up stunting the growth and stinking up the place.

What she said on both counts.