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TC asked in another thread what my cat's diet had to do with my coming up with biological phosphate recovery...

So now you all have to listen to me tell ya all about it...

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Whenever I've lived on a farm/rural setting as opposed to a city, I like to have a cat around, as well as a dog. Once the cat(s) are old enough I pretty much leave them to fend for themselves for the most part. They have all done this quite aptly and often leave "gifts" at the doorstep...dead mice, birds etc...My wife on the other hand has this wonderful maternal instinct to take care of and feed the critters even if they're perfectly capable of taking care of themselves (she's cute that way). She is also a vegan who eats almost an all raw food diet, so the cat doesn't exactly get meaty scraps from her plate or anything. So she was reading about kitty diets and what foods they shouldn't eat, and telling me about it. She listed some stuff to avoid that she found interesting (I forget what exactly) but they were vegetables to be avoided. I thought "huh, that's weird...I wonder why they can't eat such and such"...She said she thought they probably lacked some enzyme or another to digest the vegetable in question. That sounded fishy to me, and I remembered back in the states some cat food being labeled or promoted as "low magnesium", but had no idea why. So I Googled...

Turns out that the pH of the urine inside a kitty cats bladder is much higher than ours, so they tend to get painful bladder stones. So I Googled bladder stones. Turns out the stones are comprised of (MAP) magnesium-ammonium-phosphate crystals. I thought "Wow! kitty cat bladder stones would probably make an awesome fertilizer". People get bladder stones too. Made from the same MAP. This usually happens when there is an infection site present on the bladder wall. The bacteria raise the pH locally near the infection site and a crystal starts to form. If you eat a vegetable diet high in magnesium you are worse off, since the MAP crystal (called struvite) will grow until one of two things happens,

1) magnesium is all used up

2) phosphates run out or 

3) pH falls back to normal.

My next thought was something along the lines of "Jumpin' jesus on a pogo stick! I have hundreds of litres of aged human urine in the shed that has hydrolyzed to "humonia" with a pH of around 9 and got me a big ol' bag of Epsom salt (MgSo4-7H20...magnesium sulfate heptahydrate) which is about 10% Mg by weight. So I immediately went about mixing the two haphazardly together, waited for something to explode (it didn't) a white cloudy precipitate formed...I strained it through the dust catcher of my miter saw and stared at the powdery crystals...and thought "this cant be that all their is to it? did I just make struvite"? I immediately set about gathering junk material to build a "struvite reactor"...and going about the time consuming task of figuring out by trial and error, how much Mg was enough to usurp the phosphates without being too wasteful with the Mg...

So I asked for some help here on this forum and Googled a lot. It turns out I wasn't the first person to get the idea to use struvite as an agricultural fertilizer...which was good, because that probably meant that there were some studies/information to be found. Most of it has to do with animal slurry. But some basic ideas were confirmed.

The rest can be found here...

Didn't know the background on this. Interesting. Thanks for sharing.

Thanks for helping out with this Chris. That study you linked with the average phosphorous content of urine/slurry gave me the basis for my starting point in regards of how much Mg to add ...and that was the biggest question I had to all of this.

Cool Vlad, That helps explain how you started on that track.

And also why you shouldn't be feeding parsley and turnip greens to your cat (as if your cat would eat it?)

I like to learn the back stories, they can be entertaining.  Thanks for sharing it.

My pleasure. The whole idea of breaking down humonia into components interesting to traditional hydroponics methods is in my opinion even more interesting than the whole fish thing. Especially being able to do it using cheap/simple/backyard methods.  Of course both are really cool.

Any further thoughts on the nitrate conversion and/or the potassium nitrate reactions? I know you wouldn't have had time to try any out recently.

Thanks TC. I don't mind sharing. Suprisingly our cat is far less picky about eating certain veggies than our dog even...Go figure? Though, the dog likes just about every and all fruit we give him...

Chris. Nothing much going on there. I've opted to not use traditional nitre beds since I don't keep any stable animals, and just use a leftover 2/3rd IBC bottom and some straw bales. Pissing on the bales and/or just pouring humonia on them. Watching for calcium nitrate crystals to form... some finally seems to have. Adding lime should help hydrolyze the urea by upping the well as add some calcium to the mix. There's quite a bit of calcium in urine it seems, but some more should help with boosting CaNO3 quantity. After that I figured I'd leach the straw with homemade KOH and convert the CaNO3 to KNO3. I've got some clues to go on, to keep it from going "in the grease" (getting CaNO3 curds...not enough KOH) or "in the lye" (too much KOH)... It's getting pretty cold here already, so I bet the straw/urine process will be slow or come to a standstill soon. I didn't get started early enough for winter this time around...

Yeah, as much as I like the fish, I still feel that realistically they are your limiting factor. Not only as it relates to plant growth, but your ability to deal with bugs, fungal disease, BOD, electricity, solids filtration, back up systems etc...all these things can certainly be dealt with in other ways...but christ on a crutch, the fish sure do drive up your operating costs (not just their food, but all that other stuff I listed to)...Cheap and simple is good in my book, and the fish seem to be neither (all things being a matter of perspective and relative of course). I'll keep some fish to be sure, but won't be wholly relying on just them to be the engine that keeps the system going...particularly if I don't wish to add more filtration devices, other than the 8 IBC media beds. I'm just not convinced it would work long term on fish alone that way (just the media beds and worms filtering/mineralizing ALL the fish waste). I was serious about an ultra low stocking density...

I guess using the old school method is tried and tested so no need to change it for now. I guess it just takes time now, cold weather or not. The results should be interesting regardless.

All excellent points regarding fish as a limiting factor in a system. Besides the increased costs, the increased risk of a crop being going belly up is much more of a setback vs just replanting 2 weeks of lettuce too.  The romance of aquaponics seems to far out way the practicality, not to say that it isn't also very practical to an extent as well  No wonder why selling aquaponics is so much more profitable than selling the produce. Growing food with pee is not nearly as romantic an idea, to most people anyway.

Heck, I don't think it is legal to sell produce grown with pee in much of the world.  People are far too phobic.

Hence some of the 'fancy' processing. Umm... "official" disclaimer"...err...I doubt I'll be adding things like humonia or humonia based products to the big system. KCl, KOH, KHCO3, MgSO4-7H2O...Keplak for trace elements...sure. But my source water already comes with NO3 at about 17-20 mg/ L right out of the tap, so I figure I'm already ahead of the game

BTW...I shut the ball valves to four out of the 8 IBC's to help with the leaky index valve until my pump comes arrives (the stronger one) and have managed to balance out the flow between the system components that way.

I was looking at the Fimco site last nite and it says "the six way index valve can be operated with a 5 or 6 way cam" which made me worry a bit. Does that mean that even with the stronger pump the index valve will still leak out to other zones? It would be nice if you could calm this fear with some anecdotal direct experience TC. Have you ever ran a 6 way index valve with the 4 way cam? Anywhos...

Man it sure takes for ever, for small flow adjustments made in one spot, to make themselves manifest at the other end, in a system with 18,000 litres of water. It takes a good amount of time for water to flow though those four DWC troughs.

NH4/NH3 is at 3 mg/ L nitrites yet, but plenty of nitrates (from the source water)... pH is about 8.3 seedlings are not minding that (yet), so I haven't bothered to lower the pH at all. Water temps are a cool 16-17 Celcius. Finally cycling the beast...

I've used the 6 way indexing valves with 3 and 4 zone cams as well as 2, 5 and 6 zone cams.

I usually use a temporary method to cap the unused outlets (for me that means a rubber coupler and a slip plug)  I usually use those flexible couplers to hook up the indexing valves to make it easier to change things out later if need be.

Even with a strong pump there is sometimes a trickle out the inactive outlets but once the stronger pump is going you should get a better seal and the flow out the active outlet should be strong enough to flood that bed while the trickle shouldn't make a difference in the other beds (assuming timed flood and drain with stand pipes with holes.)  Indexing valves are not meant to be used with siphons.

Thanks TC, that's all the comforting I needed. . The 2 unused outlets are securely yet temporarily capped off. The trickle doesn't necessarily cause a problem in the other media beds, but rather in the nursery trough that all the beds empty into before water flows to the DWC production/grow-out troughs...With the weaker pump, more water is being sent to the nursery troughs (due to the disk not being properly seated by the needed pressure). The outlet on the nursery trough is a 1-1/2" bulkhead with a male threaded adapter. The wall thickness of the adapter reduces the bulkhead diameter to 1-1/4"...So while it's ok to have 4 beds draining simultaneously ( 8,  1/4" drain holes...2 1/4" drain holes per standpipe) the excess leakage to un-wanted zones is causing too much un-wanted and un-necessary flow into said nursery trough...both from flow through unwanted zone as well as increasing the flood time for the wanted beds due to that water being diverted to an unwanted zone...make sense.

I gave myself some wiggle room for the nursery trough to not over flood, but still...cutting it close.

The technical data sheet on the Fimco site and the way that it was stated led me to wonder...if this sort of leakage would persist even with the stronger pump. It's quite a bit. 1/3rd of total flow (give or take) so I'm quite sure that it is the pump being to weak to engage the disk properly. Just wanted to hear you negate my interpretation of the info on Fimco's site, that's all...In my head the matter is now settled. Still waiting for the stupid pump (the proper one that I originally wanted) to come in. Been waiting since the beginning of August. The importers shipment of Atman magnetic drive pumps finally arrived Oct.16, then some 'Ministry of Financial Blablabla" found that the importer lacks some new document/stamp to release/sell them on the market here (even though they've been doing so for years). So the entire shipment of pumps are in limbo until the proper official is bribed...The other importer of pumps now sells bird food and doesn't deal in pumps anymore. I've made other arrangements in the mean time to "smuggle" a pump in from Italy...Christ, it'd be easier to deal in heroin here than AP. Heroin, beer and cigarettes, you can always get, guns can't forget all the guns too...But dimensional lumber...drywall screws...PVC fittings...fountain pumps...forget it. You might as well be trying to buy Pelican's milk... This type of non-sense has been totally indicative of my experience here this past year. Anyhow, sorry for the rant...thanks for clearing up that up (4-way cam on a 6 way valve)...

I'm not quite sure how water trickling out inactive zones would really affect the nursery bed if all beds are draining through it.  When you get a stronger pump, you will have more flow and even if all the flow is going through just one bed, that bed draining into the nursery bed when it reaches full flood and is draining down the top of the stand pipe is going to be more flow than you currently get from the smaller pump.

If things are close now, you better do some re-thinking before putting the bigger pump online.

The way I usually do the indexing valves, I have pretty much constant flow coming out of grow beds.  It will peak when a bed is at full flood and water is draining down the top of the stand pipe but then eases back a bit while the valve starts filling the next bed, (that is the repeat cycle timer only turning the pump off for about a minute at a time to switch zones.) so if all beds were draining into a single other bed, there really won't be much in the way of drain time the way I do it because there is always a bed or two or three draining all the time.


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