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ITT we discuss Decoupled / Open loop / Multi-circuit aquaponics systems

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I think the disconnect is people not realizing that wastewater treatment and mineralization are the same processes, biologically speaking. The main difference is that wastewater plants have more chemicals to deal with than just organic wastes.

 

There's plenty of pdf's and links posted and if more questions are concerned about that then another thread might be warranted.

 

As someone who grows duckweed by the tonne. I need to point out that duckweed does require more nutrients than just nitrogen and needs all the nutrients as much as other green growing plants. Remember you are told to eat green leafy vegetables , because they are high in iron , calcium, and magnesium. The same holds true for duckweed.  FYI, duckweed grows well in shade, just not as fast, and also grows in cold water down to the high 50'sF , but growth rate is slowed.

 

A duckweed loop on the fish side has been used by a commercial aquaculture facility in the past and might be way at reducing water exchange and evaporation as long as oxygen needs are met.

Edited by Ravnis (see edit history)

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Btw talking about greens and adjusting ph for plant and fish optimal specs.  Since greens tend to prefer ph 6.5-7.5 ish and fruiting plants  are reported to do better around 6.   Do you put your greens with the fish loop?

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Btw talking about greens and adjusting ph for plant and fish optimal specs.  Since greens tend to prefer ph 6.5-7.5 ish and fruiting plants  are reported to do better around 6.   Do you put your greens with the fish loop?

 

The entire hydroponics industry.. and a lot of science would suggest those pH figures are quite a way out Ravnis

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The entire hydroponics industry.. and a lot of science would suggest those pH figures are quite a way out Ravnis

 

That's curious, and different than what I've read.  Just an example:

 

https://pubs.ext.vt.edu/426/426-408/426-408.html

 

Though you have more experience with hydro than I, so will defer. 

 

Why such a difference in literature. That's not the only source I've seen that lists those ph.

 

Edited by Ravnis (see edit history)

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Humm... interesting choice to use Sodium Nitrate...

 

Wonder if the results observed were due totally to the high level of "nitrates"... or possibly due to high levels of sodium... or a combination...

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I agree... my entire interest is and has been aerobic digestion of aquaculture waste from the very beginning here...

 

trying to figure how what you are writing applies to our context... that's all, all of the rest doesn't really matter. 

 

anaerobic digestion producing the least refractory solids is awesome... how is this and is it reasonable to be applicable to us?

 

Since water content of fish waste (in hobbyist context) is so incredibly high... Wouldn't wastewater treament concepts also be just as applicable to us?

 

If I recall correctly, the reason we got onto wastewater treatment was that you were hell-bent on revealing what you didn't know about anaerobic digestion.

 

The entire reason why anaerobic digestate becomes created is due to the fact that anaerobic digestion does NOT "produce much less refractory solids" than aerobic digestion, which is why anaerobic digestate requires to be further broken down aerobically. Think about it...  ;)

 

Since wastewater treatment processes are the source of original truth on most of what happens in recirculating aquaculture (and aquaponics) it can be seen to be relevant. Anaerobic digestion is only relevant to us (as far as I'm aware) inasmuch as it relates to denitrification.

 

Thinking about that for a moment, if we were looking to reduce the nitrogen levels while retaining most of the other minerals in fish tank water, we might include an (offline) anaerobic link in the chain.  We'd need to determine what sort of retention period is required for the nitrogen to be converted - and we'd need to consider what carbon source we'd use to achieve the denitrification.  

 

Thinking back to the "Really Smart Guy" thread on BYAP (years ago), I think it would be a relatively short retention time….possibly no more than a couple of days.  I'd need to think about it a bit more….but it might be a 3-step process…...aerobic - anaerobic - aerobic.  That would provide a liquor that is low(er) in nitrogen but everything else should be intact.  The final aerobic stage would allow for degassing of the nitrogen (which by then is a gas)…..and carbon dioxide.

 

In this situation, you wouldn't be concerned about refractory solids because the anaerobic digestion wouldn't extend to the production of methane (just CO2)…..and it's the methane production that leads to the reduction of refractory solids.

 

Does that help?

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Btw talking about greens and adjusting ph for plant and fish optimal specs.  Since greens tend to prefer ph 6.5-7.5 ish and fruiting plants  are reported to do better around 6.   Do you put your greens with the fish loop?

 

Do a Google search with the words "agriculture extension" in it... You will find that most documents will indicate Spinach is the "odd man out" when comes to enjoying more alkaline pH... Most others are around 5.5~6.5 for lettuce greens... Depending on which article, might say up to 7.0 on the high end range. Generally, I would approach the situation as "high end range" is not necessary a good deal due to how the nutrients start to change above a neutral pH.

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If I recall correctly, the reason we got onto wastewater treatment was that you were hell-bent on revealing what you didn't know about anaerobic digestion.

 

just trying to wrap my head around what I read on wikipedia... which stated the byproduct of anaerobic processes is digestate and biogas and that the digestate was then required to be further decomposed aerobically since there are aspects that anaerobic digestion fails to decompose... You have not yet showed how this is false..

 

Sorry Gary... I was not "hell-bent on revealing what I didn't know about anaerobic digestion"... unfortunate that you wanted to viewed it as such... I am not here to score points...

 

My apologies for I did not realize you were a wastewater treatment professional... Still... I don't understand...

 

 

Thinking back to the "Really Smart Guy" thread on BYAP (years ago), I think it would be a relatively short retention time….possibly no more than a couple of days.  I'd need to think about it a bit more….but it might be a 3-step process…...aerobic - anaerobic - aerobic.  That would provide a liquor that is low(er) in nitrogen but everything else should be intact.  The final aerobic stage would allow for degassing of the nitrogen (which by then is a gas)…..and carbon dioxide.

 

In this situation, you wouldn't be concerned about refractory solids because the anaerobic digestion wouldn't extend to the production of methane (just CO2)…..and it's the methane production that leads to the reduction of refractory solids.

 

Does that help?

 

No... not really... since I don't care about off gassing my nitrates...

Edited by crsublette (see edit history)

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Humm... interesting choice to use Sodium Nitrate...

Wonder if the results observed were due totally to the high level of "nitrates"... or possibly due to high levels of sodium... or a combination...

Thanks for pointing that out

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That was my thought too John - there seemed to be some other variables at play other than nitrates.

From personal experience my trout systems have run with 200ppm+ nitrates with no fatalities or deformities.

Good with info from experience. Thanks

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just trying to wrap my head around what I read on wikipedia... which stated the byproduct of anaerobic processes is digestate and biogas and that the digestate was then required to be further decomposed aerobically since there are aspects that anaerobic digestion fails to decompose... You have not yet showed how this is false..

 

Sorry Gary... I was not "hell-bent on revealing what I didn't know about anaerobic digestion"... unfortunate that you wanted to viewed it as such... I am not here to score points...

 

I think we all understand exactly what was happening.  ;)

 

My apologies for I did not realize you were a wastewater treatment professional... Still... I don't understand...

 

I'm no longer anything to do with wastewater treatment…..but i have found it interesting that so much of what I encounter in aquaculture/aquaponics is familiar to me - for entirely different reasons.  In my wastewater treatment days, we thought of nutrients as problems to be resolved; in aquaculture they are opportunities to be exploited.  Don't be concerned about not understanding……it happens to us all at various times.

 

No... not really... since I don't care about off gassing my nitrates...

 

I understand that you have yet to build your first aquaponics system so your interest is (to this point anyway) largely academic.  I posed the question for the consideration of the broader group…..among whom there may be some who have an excess of nitrogen that is problematic.  The scientific/medical community have expressed concern about the nitrate levels in some foods.

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Quote Toga from a previous thread, that was locked.

 

 

I encourage all members to employ a level of self moderation;

 

Does your post address the topic ?... or the person ?

Is your post accurate ?

Is your post relevant ?

Is your post offensive ?

Is your post put forward in the best possible light ?

Is your post suitable to be read by all denominations of our forum members ?

 

If you think for even one second that your post might be questionable... Do Not Post It !

 

 

Thank You

Toga

APN Moderator Team

 

 

*edit* Perhaps this post should be auto generated every 4th or 5th post.

Edited by Toga (see edit history)

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Do a Google search with the words "agriculture extension" in it... You will find that most documents will indicate Spinach is the "odd man out" when comes to enjoying more alkaline pH... Most others are around 5.5~6.5 for lettuce greens... Depending on which article, might say up to 7.0 on the high end range. Generally, I would approach the situation as "high end range" is not necessary a good deal due to how the nutrients start to change above a neutral pH.

 

Had already done that and where the range had originally come from.   That document list kale, cabbage, collard, etc.

 

Found conflicting research from Cornell around the 5.6-5.8 level.  

 

Guess I shouldn't trust this chart either  http://www.gtghydroponics.com/faq/veggieph.aspx

 

The odd thing is I've seen great growth of greens at ph of 8 to as low as 6.   PH below 6 actually retarded growth in one system.  Make one wonder just really how important PH really is as a parameter.  Of course, great growth is not necessarily optimum.  Still it makes one wonder just really how important PH  is as a parameter

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pH dictates trace element take up.. or lock out...

 

That's why hydroponics is usually in the range of 5.8 - 6.6... or was...

 

Current hydro industry practice is actually more like 5.2 - 6.2 ... ;)

 

You will find that most documents will indicate Spinach is the "odd man out" when comes to enjoying more alkaline pH...

 

That's totally dependent on Spinach species type... as Paul found out...

 

Spinach can be a "canary" indicator of Iron deficiency... and Iron is one of the first elements locked out with a pH above 6.8....

Edited by RupertofOZ (see edit history)

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So  it looks like NFT is the method of the day.being push by hydro shops here in the US,  with a decoupled loop is this the best way to grow?    Finding DWC in larger that 4' x 4' trays can be like finding a needle in a haystack.  Does DWC hold any benefit to make it worth the effort  to construct vs buying off the shelf NFT commercial grade equipment.  A lot of times DIY can be just as costly in the end as purchasing commercially and hopefully professionally made.

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Hi c

just trying to wrap my head around what I read on wikipedia... which stated the byproduct of anaerobic processes is digestate and biogas and that the digestate was then required to be further decomposed aerobically since there are aspects that anaerobic digestion fails to decompose... You have not yet showed how this is false..

here is a postprint publication, on anearobic digeston of solids waste in ras http://orbit.dtu.dk/services/downloadRegister/104540082/Anaerobic_digestion_of_solid_waste_in_RAS.pdf  (Rainbow trout wastes)

from here http://orbit.dtu.dk/en/publications/anaerobic-digestion-of-solid-waste-in-ras-effect-of-reactor-type-on-the-biochemical-acidogenic-potential-bap-and-assessment-of-the-biochemical-methane-potential-bmp-by-a-batch-assay%289a71b79d-2e0f-4710-826c-4791ded58a91%29.html

 

 

cheers

Edited by ande (see edit history)

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http://acqualogic.com/wastewater/

 

An example of multistage digester.  The FLora filter just screams for plant growth. 

 

Anyways, regardless of the benefits or risks of the varying mineralization/treatment options employed, there are still two complete systems that have to be built:
 

Aquaculture and  hydroponic system.    The aquaculture system will need :   gas exchange system, filtering system for solid waste, and biofiltration   for dissolved wastes.    

 

So as RC or others build there system what attributes affects design choices in each of those categories?   Which ones are more beneficial in a particular scale.

Edited by Ravnis (see edit history)

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What is it with this obsession with anaerobic digestion... in an AP secenario...

 

It will take 14+ days to get to hydrogen sulphide and/or methane.. minimum...

 

That alone suggests that having an "anaerobic" stage in-line with any other stages.. is a complete nonsense and waste of time.. for NO benefit....

 

The stages of anaerobic digestion.. (as in the RSG thread).. are all "reductive"... in the absence of oxygen the bacterial processes scavenge oxygen from other compounds... (or as Paul said in his podcast Mathias)... they donate electrons down the line...

 

In the order... NO3 (nitrates) = > Metallic oxides, especially Iron oxide (see RSG thread).. => sulphates (sulphides... hence hydrogen sulphide)... to ultimately the only thing left is carbon and hydrogen... which becomes methane...

 

Any "in-line" mineralisation system with a first stage anaerobic process wiould hardly be more than a few days at best...... if you're not draining your solids from the solids filters quicker than that... you're just moving your anaerobic digestion back into the fish loop... :D

 

If the retention time is less than a few days... then the only possible thing that might occur... is nitrate reduction.....

 

Why would you want to reduce your nitrates.. if your intention is to produce an end product to feed your plants :o

 

If you want to do anaerobic digestion of any sludge left from aerobic mineralisation.... dump it into a decoupled sealed tank outside.. let it sit and use the methane if you want....

 

But there's NO benefit of anaerobic digestion for fish or plants.... !!!!!!!!!!!!!!!!! .... and potential dangers... !!!!!!!!!!!!!!!!!!!!!!!!!!

 

The human body doesn't organize it's nutrient breakdown and growth potential... by sticking its bowel and anus before it's stomach....

 

Decouple your minds from bloody anaerobic digestion... leave it outside in your humanure compost methane toilet... where the poop belongs... :D

Edited by RupertofOZ (see edit history)

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Hi ROZ

What is it with this obsession with anaerobic digestion... in an AP secenario...


 

But there's NO benefit of anaerobic digestion for fish or plants.... !!!!!!!!!!!!!!!!! .... and potential dangers... !!!!!!!!!!!!!!!!!!!!!!!!!!

 

The human body doesn't organize it's nutrient breakdown and growth potential... by sticking its bowel and anus before it's stomach....

 

Decouple your minds from bloody anaerobic digestion... leave it outside in your humanure compost methane toilet... where the poop belongs... :D

There is no obsessions.

In colder climates they are a common part of the RAS (and increasingly so), you produce/harwest fertilzer, and use the methan onsite, integrated in the production line.

It's all a matter of, scale/volum/location/specie/etc.

 

cheers

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In colder climates they are a common part of the RAS (and increasingly so), you produce/harwest fertilzer, and use the methan onsite, integrated in the production line.

It's all a matter of, scale/volum/location/specie/etc.

 

That may well be true Ande...

 

But are the anaerobic process integrated in the production line themselves... or actually "decoupled" and the end product returned/used....

 

I doubt they'd have their anaerobic digester in their RAS fish loop....

 

I'm not opposed to using an anaerobic digester .. to reclaim/reuse the resultant "sludge".. conversion into methane for lighting/heating... or even just composting it....

 

I just suggest.. (back several posts)... that it should be decoupled from any fish/plant/mineralisation loop....  there seems to be quite a few examples where that's not the case... ;)

Edited by RupertofOZ (see edit history)

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Hi ROZ

 

 

But there's NO benefit of anaerobic digestion for fish or plants.... !!!!!!!!!!!!!!!!! .... and potential dangers... !!!!!!!!!!!!!!!!!!!!!!!!!!

Not if decoupled, in a propper design it want be inline with either one to represent any dangers

 

 So no dangers, unless you are thinking about the dangers related to a gas explotion in the plant .

 

cheers

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Not if decoupled, in a propper design it want be inline with either one to represent any dangers

 

Agreed.. see post above as you were posting... and I said that before.... decouple it and leave it out the back... it has no place in the fish/plant/ mineralisation loops... or more specifically... no place "in-line"...

Edited by RupertofOZ (see edit history)

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Rupert,

 

As long as you're talking about attempting methane production, I agree with everything you've said.  The numbers just don't stack up for anything less than the largest aquaculture operations.

 

Nitrate reduction, however, may be an issue for some people.  As I've said, high nitrate levels in some foods are a health concern.   Most of us grow food for our own use (and that of our families and friends) so the last thing we want to do is produce food which is somehow unhealthy.  I can't think of practical examples off-hand but there may be plants that require little nitrogen (but all of the other goodies).

 

The old mantra of "add more grow beds" is not always practical or desirable……any more than is running a system at half throttle to limit nitrate production. 

 

Anaerobic digestion is a means of facilitating nitrate reduction……and it doesn't have to extend to methane production.   Retaining the water in an oxygen-free conditions……possibly for as little as a day or two…..will facilitate denitrification…..and the only gas that will be problematic will be CO2….and that will gas off with the nitrogen as soon as the water passes back into an aerobic environment.

 

I agree that anaerobic digestion, should it be found to be desirable for whatever reason, be done off-line…..but I'd provide the same advice for anything that is likely to demand oxygen of the system over and above that required by the fish….and the nitrifying bacteria.

 

Gary

Edited by Gary Donaldson (see edit history)

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