Strider

Dual loop system build.

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I was under the impression ph should fall in a healthy aerobic MT. So mine has been worknig fine all along with a rising ph?

You know I read a lot about MTs and what they do but honestly I am not sure anyone really knows. Mine also works in a higher than neutral Ph climate. So if they are supposed to keep Ph low I find no evidence of such.

Edited by Strider (see edit history)
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I was under the impression ph should fall in a healthy aerobic MT.  So mine has been worknig fine all along with a rising ph?

In a trickle filter with lots of solids I am under the impression that you may have some denitrification (depending on how you operate the trickling filter and based on what media you are using) you should also have nitrification in the lower areas of the trickling filter.

So with that, as protein is being mineralized to ammonia then oxidized to Nitrates within the trickling filter (assumption based on what I have read) The ph in the trickle filter/MT should possibly drop a little or stay neutral.

 

When you then add the MT water (High in nitrates by now if nitrification is happening in trickle/MT) the plant's take up the nitrates and that process causes pH to go up in the plant loop. Now if you transfer water from the RAS straight from fish tank, the water should contain more Ammonia if you time it good. By transferring that to the plant sump (NOT TO THE MT) then the plant sump and whatever grow bed you are using will handle the nitrification, this will lower pH and then of course as plants uptake nitrates that will increase pH. So you can help balance the system to some degree by dosing correctly from the correct source as needed.. Does that make sense?

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The precise layout of a dual loop system - and the components used - will depend on your production goals.

 

In some situations, ridding the system of nitrates will be important (particularly if you are running lots of fish while growing lettuce) where, in other situations, you'll want the nitrates.....and everything else that can be squeezed out of the fish food.

 

Sometimes, dual loop systems will be used for other reasons......like avoidance of pH and temperature compromises.....and some people will be operating dual loops for water quality management or disease management purposes.

 

There's no "one size fits all" approach to dual loop......and knowing what you hope to achieve from it is the key to its successful utilisation.

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Lmannyr you are right. In a MT there is an abundance of heterotrophic bacteria where as in a MBBR (biofilter and no solids) there are auto trophic bacteria. A mt that goes completely anaerobic will drop pH But it will increase as soon as you add air. Air helps strip the co2 which is making the water acidic during anaerobic conditions. Now if you have anaeobic zones in an aerated MT the pH will go up as the co2 is offgassed This is why people notice pH increasing in their MT. (i think) :)

Seems like it should be the other way around. In my fish side I get a Ph drop yet I have plenty of O2 in my bio filter and FT. My RFF is empty and even after I clean it my Ph still drops. So I have to assume the Ph drop is due to the MT doing what it does. It may be interesting to bypass the MT and see what effect that has on my Ph levels...

Edited by Strider (see edit history)

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The precise layout of a dual loop system - and the components used - will depend on your production goals.

In some situations, ridding the system of nitrates will be important (particularly if you are running lots of fish while growing lettuce) where, in other situations, you'll want the nitrates.....and everything else that can be squeezed out of the fish food.

Sometimes, dual loop systems will be used for other reasons......like avoidance of pH and temperature compromises.....and some people will be operating dual loops for water quality management or disease management purposes.

There's no "one size fits all" approach to dual loop......and knowing what you hope to achieve from it is the key to its successful utilisation.

My reason for going to dual loop was just what you mentioned...., to be able to control each loop independantly of the other. But the big challenge for me is to get the natural Ph levels flipped so that the fish side stays above 7 and the plant side stays below.

So to me that means I have to duplicate the conditions causing those Ph levels and incorporate those into each loop.

On the fish side I will assume my Ph decrease is being caused by the Bio filter. So I will add media to the plant side MT and see if that drops the plant side Ph.

Not sure there is a similar solution for the fish side.

Edited by Strider (see edit history)

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In a trickle filter with lots of solids I am under the impression that you may have some denitrification (depending on how you operate the trickling filter and based on what media you are using) you should also have nitrification in the lower areas of the trickling filter.

So with that, as protein is being mineralized to ammonia then oxidized to Nitrates within the trickling filter (assumption based on what I have read) The ph in the trickle filter/MT should possibly drop a little or stay neutral.

 

Trickle filters should be thin (bio)film and have very little oxygen gradient in the film; thus should be pure aerobe and without any denitrification.

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Seems like it should be the other way around. In my fish side I get a Ph drop yet I have plenty of O2 in my bio filter and FT. My RFF is empty and even after I clean it my Ph still drops. So I have to assume the Ph drop is due to the MT doing what it does. It may be interesting to bypass the MT and see what effect that has on my Ph levels...

In an aerobe MBBR you have hetrotrofic bacteria activity (all the small solids which pass your solid removal unit) as well as nitrification, if the filter is too small there will be competition for space and nitrification will be suppressed. Both processes will lower pH.

Anaerobe processes (denitrification) will raise pH.

In a anaerobe digester (mineralization) both processes might happen and thus pH might rise or fall.. Depending on flow and design.

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Trickle filters should be thin (bio)film and have very little oxygen gradient in the film; thus should be pure aerobe and without any denitrification.

Should? Depends on the process/setup. Read up on Bio film in trickling filter and you will find that deep within the Bio film some denitrification is occuring.

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Seems like it should be the other way around. In my fish side I get a Ph drop yet I have plenty of O2 in my bio filter and FT. My RFF is empty and even after I clean it my Ph still drops. So I have to assume the Ph drop is due to the MT doing what it does. It may be interesting to bypass the MT and see what effect that has on my Ph levels...

PH drop in an aerobic system with nitrification is happening due to the process of the autotrophic bacteria using up "alkalinity".

In anerobic conditions heyerotrophic bacteria is eating organic material and the the leftovers are lots of CO2 and ammonia. Co2 lowers pH under anaerobic conditions but as soon as that water is being aerated the air will start to strip the water of CO2 which then results in an increase in pH.

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PH drop in an aerobic system with nitrification is happening due to the process of the autotrophic bacteria using up "alkalinity".

Ok, so would that nitrification process be accuring primarily in the bio filter where the k1 media is housed? If yes, then would it not stand to reason that if I duplicate that on the plant side a Ph drop will happen?

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Ok, so would that nitrification process be accuring primarily in the bio filter where the k1 media is housed? If yes, then would it not stand to reason that if I duplicate that on the plant side a Ph drop will happen?

Will only work if you have some ammonia.

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Should? Depends on the process/setup. Read up on Bio film in trickling filter and you will find that deep within the Bio film some denitrification is occuring.

Main advantage of using a trickle filter is the good gas/liquid ratio's. This is achieved with void spaces in filter material & proper design. In my book hydraulic load on filter has to be high enough to keep biofilm thin enough to avoid anaerobe processes (thus they need to be self cleaning). This result in a very stable filter with huge abilities in shock loads of nutrients. In my experience better then MBBR, however energy use for trickle filters is higher and that's the main reason that these are less populair now.

Anaerobe processes in trickle filters can be quite dangerous as large quantities of toxins can be released in a short time. I did some work at a barramundi farm with problems in the trickle filters and besides allivated background mortality fish had problems with CO2 levels and had all sort of weird secondairy skin infections. They had to unpack the filters and redesign.

Nowadays if I have to troubleshoot a commercial farm I get them to sent a water sample to the lab and let them determine bacterie count of obligate anaerobe and aerobe bacteria and this gives me info on uncontrolled anaerobe spots in the system.

 

Don't believe everything which is published on the web, quite some of the info comes from people who have no clue themselfs.

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Main advantage of using a trickle filter is the good gas/liquid ratio's. This is achieved with void spaces in filter material & proper design. In my book hydraulic load on filter has to be high enough to keep biofilm thin enough to avoid anaerobe processes (thus they need to be self cleaning). This result in a very stable filter with huge abilities in shock loads of nutrients. In my experience better then MBBR, however energy use for trickle filters is higher and that's the main reason that these are less populair now.

Anaerobe processes in trickle filters can be quite dangerous as large quantities of toxins can be released in a short time. I did some work at a barramundi farm with problems in the trickle filters and besides allivated background mortality fish had problems with CO2 levels and had all sort of weird secondairy skin infections. They had to unpack the filters and redesign.

Nowadays if I have to troubleshoot a commercial farm I get them to sent a water sample to the lab and let them determine bacterie count of obligate anaerobe and aerobe bacteria and this gives me info on uncontrolled anaerobe spots in the system.

Don't believe everything which is published on the web, quite some of the info comes from people who have no clue themselfs.

We may talk about using a trickling filter in two very different applications. For a biofilter in a RAS I can see your point. But as a mineralization trickling filter there will be quit heavy organic loading of the filter. More along the lines of how a trickling filter is being used in wastewater treatment.

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Will only work if you have some ammonia.

Yes, and the ammonia will come from the twice daily drain from the fish side to the plant side MT...

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Yes, and the ammonia will come from the twice daily drain from the fish side to the plant side MT...

Sounds like you got it figured out. Let us know how the pH control works out for ya.

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We may talk about using a trickling filter in two very different applications. For a biofilter in a RAS I can see your point. But as a mineralization trickling filter there will be quit heavy organic loading of the filter. More along the lines of how a trickling filter is being used in wastewater treatment.

 

I would have thought that there would be better mineralisation options than trickling filters.

 

A wastewater treatment plant trickling filter is a biological filter......they are located downstream of the rakes and primary sedimentation tanks.  As such, the organic loading is not particularly heavy.   The wastewater treatment equivalent of a mineralisation tank would be the stabilisation lagoons which had a capacity equal to 42 days of daily flow (about 32 megalitres/day if I recall correctly)  

 

Algae growing in the effluent would reduce the biological oxygen demand to the point where the water was allegedly OK to discharge into the Gulf.  There was some debate about this since the seagrass was killed off for miles around the point where the effluent was discharged into the sea.

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Main advantage of using a trickle filter is the good gas/liquid ratio's. This is achieved with void spaces in filter material & proper design. In my book hydraulic load on filter has to be high enough to keep biofilm thin enough to avoid anaerobe processes (thus they need to be self cleaning). This result in a very stable filter with huge abilities in shock loads of nutrients. In my experience better then MBBR, however energy use for trickle filters is higher and that's the main reason that these are less populair now.

Anaerobe processes in trickle filters can be quite dangerous as large quantities of toxins can be released in a short time. I did some work at a barramundi farm with problems in the trickle filters and besides allivated background mortality fish had problems with CO2 levels and had all sort of weird secondairy skin infections. They had to unpack the filters and redesign.

Nowadays if I have to troubleshoot a commercial farm I get them to sent a water sample to the lab and let them determine bacterie count of obligate anaerobe and aerobe bacteria and this gives me info on uncontrolled anaerobe spots in the system.

 

Don't believe everything which is published on the web, quite some of the info comes from people who have no clue themselfs.

 

Thanks Phri for your insight.

 

I have always wondered.... Do aquaculture farms do maintenance on their trickle towers, such as an occasional rinse, in attempt to control the population of obligate anaerobes? Or is this too expensive endeavor due to how the trickle towers are built, thus are not conducive to being rinsed so easy?

 

What do you do for CO2 stripping or other gaseous exchange if you do not use a trickle tower? Is a MBBR is more than sufficient for this?

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Thanks Phri for your insight.

 

I have always wondered.... Do aquaculture farms do maintenance on their trickle towers, such as an occasional rinse, in attempt to control the population of obligate anaerobes? Or is this too expensive endeavor due to how the trickle towers are built, thus are not conducive to being rinsed so easy?

 

What do you do for CO2 stripping or other gaseous exchange if you do not use a trickle tower? Is a MBBR is more than sufficient for this?

A good designed trickle tower is virtually maintenance free. Some designs use spray noozles for water distribution on top and these need cleaning now and then, especially if they are used on low pressure.

 

There are big differences in filter material for trickle filters and each type of material is going to give you a different preformance (like k1 & k3 for mbbr); it's not only about SSA (specific surface area). Some trickle filter blocks have very smooth surfaces which gives you limited biofilm, thus limiting biofilteration but very good degassing, while other are rougher; thick biofilm very good nitrification but more chance of blockage.

 

A low energy mbbr can be considered co2 neutral (produces the same amouth of CO2 as it removes). Thus will result in CO2 problems in high stocked systems. You can increase the air input to increase CO2 stripping in the mbbr or have a dedicated degassing section in the filter. The last is typical a degassing tower or the like. The other thing is pH contfrol; mbbr typical need to run at a higher pH then trickling filters. Interestingly this makes the trickle filter fit better in an aquaponic system from the perspective of water quality management.

 

btw the above is only relevant in high density systems; currently in the system I have at home I keep 10 kg murray cod in a 2 m3 tank with a 5 m3 mbbr with little air at a pH of around 6. NO problems here, but if I up biomass to 500 kg I have to run this completly different including active CO2 control.

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A good designed trickle tower is virtually maintenance free. Some designs use spray noozles for water distribution on top and these need cleaning now and then, especially if they are used on low pressure.

There are big differences in filter material for trickle filters and each type of material is going to give you a different preformance (like k1 & k3 for mbbr); it's not only about SSA (specific surface area). Some trickle filter blocks have very smooth surfaces which gives you limited biofilm, thus limiting biofilteration but very good degassing, while other are rougher; thick biofilm very good nitrification but more chance of blockage.

A low energy mbbr can be considered co2 neutral (produces the same amouth of CO2 as it removes). Thus will result in CO2 problems in high stocked systems. You can increase the air input to increase CO2 stripping in the mbbr or have a dedicated degassing section in the filter. The last is typical a degassing tower or the like. The other thing is pH contfrol; mbbr typical need to run at a higher pH then trickling filters. Interestingly this makes the trickle filter fit better in an aquaponic system from the perspective of water quality management.

btw the above is only relevant in high density systems; currently in the system I have at home I keep 10 kg murray cod in a 2 m3 tank with a 5 m3 mbbr with little air at a pH of around 6. NO problems here, but if I up biomass to 500 kg I have to run this completly different including active CO2 control.

Thanks for your explanation. What's makes the mbbr more sensitive to pH over a trickle filter?

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:thumbsu:

 

Very awesome Phri. Thank you for this. I appreciate this. Do not let the arm chair (forum) generals create too much aggravation for ya since we (hobbyists) have been basically limited to unconventional knowledge accepted as the standard bearer due to the practice of repetition. Paul van der Werf, another professional like your self, has attempted to correct much of this (with much success at his Earthan Edge website) and I am glad to read that you are here to help out with creating clarification. I look forward to reading what you have to say in the future.

 

I am definitely a hobbyist and you are definitely a professional. I am in no way insulted in saying this, I completely respect what you have to say, whereas I know other hobbyists would likely be quite insulted by this due to their egalitarian perspective since they believe their technical acumen within aquaculture can rival or match the technical acumen as a professional as your self. Don't let this aggravate ya; unfortunately, I honestly say that I think hobbyists and niche farmers, not much different than academics, (especially in the organic holistic realm) probably have the most inflated egos within agriculture that I have ever witnessed.

 

So... Thanks again Phri. I absolutely look forward to read what you have to say in the future. You are definitely worth reading. :rock:

Hello Charles,

 

I'm uncertain as to why this little 'straw man' rant occurred but I am practising infinite patience this week so I'm  going to let it pass with a (re)statement of the following facts:

  • Paul left APN of his own volition.
  • Professionalism is as much a state of mind as it is an indicator of expertise.   There are full-time professionals and part-time professionals.....and even non-practising professionals.  Hobbyists and full-time professionals are extremes of a continuum......there are other degrees in between.
  • Being egalatarian is deemed to be a virtue in Australia.....and it probably still is in the US in most people's minds. 
  • Every person on APN is entitled to a point of view......always have been and always will be.  Anybody who can't accept that is invited to pursue their interests elsewhere (or words to that effect).

I believe that everyone on APN (and elsewhere) is, by now, aware of the various points of view around these matters......so why don't we just leave it there?

 

Gary

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Thanks for your explanation. What's makes the mbbr more sensitive to pH over a trickle filter?

That's not what I mean; due to relative average degassing, systems with a mbbr as biofilter require to operate at a higher pH to keep CO2 at exceptable levels. While with trickling filters degassing can be so good that systems can run at a pH below 6 without problems (if you fish can handle this...). Obvious this is only relavant if lots of CO2 is produced.

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So TF design is key.  Not sure I need both an MBBR and a TF on the fish sidce. I use a MBBR for ammonia and Nitrate control on the fish side but my Ph is the constant and on going issue.  I did read the "kitty liter filter" paper and I may just have to incorporate one of those on the fish side to limit some of the ammonia and Nitrates being produced. I do not want to get it to zero but rather just limit it to a reasonable and usable level that still gives the plants what they need while keeping the fish happy.  It may even increase my Ph levels.   :)

Edited by Strider (see edit history)

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So TF design is key.  Not sure I need both an MBBR and a TF on the fish sidce. I use a MBBR for ammonia and Nitrate control on the fish side but my Ph is the constant and on going issue.  I did read the "kitty liter filter" paper and I may just have to incorporate one of those on the fish side to limit some of the ammonia and Nitrates being produced. I do not want to get it to zero but rather just limit it to a reasonable and usable level that still gives the plants what they need while keeping the fish happy.  It may even increase my Ph levels.   :)

 

Hi Jim,

 

One of the key benefits of dual loop systems is avoidance of compromises around things like pH and temperature.   You can run your fish side at around 7.5 - which is good for them and the nitrifying bacteria - but which sees several nutrients locked out - and your plant side at 6.0......which optimises nutrient availability.

 

If you are going to run elevated pH levels on your fish side, you'll need to watch ammonia levels pretty closely since ammonia becomes more toxic at higher pH.

 

Gary

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More important benefit of elevated pH levels within the range for optimal nitrification, with a properly built bio-filter, there is zero concerns of nitrite and ammonia spikes (especially when coupled with a trickle filter) accumulation due to the significantly increased ammonia to nitrate conversion rate efficiency of nitrification. In the koi hobby, I have seen incidents of significant fish food accidents occurring and still not impact ammonia/nitrite water quality whatsoever.

 

Further, the dual loop allows the operator to utilize manure from other warm blooded species in the grow system without concern of this allowing spiked urea contaminants entering the fish tank.

 

 

All thanks to Paul Van der Werf at Earthan Edge for being the only one actively encouraging this and actually educating folk on how to do this and actively showing how this is done in a large scale commercial and backyard hobby arena.

Edited by crsublette (see edit history)
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