JeffH

Heredia, Costa Rica Prototype Build

69 posts in this topic

I'll update this thread with information about my iAVs build in San Isidro, Costa Rica. I am interested in exploring a relatively simple iAVs system so will be using an IBC tank for the fish and building a simple wooden box with a plastic liner to hold the sand. Still locating some of the components but I will update as I make progress.

 

san_isidro_prototype_1.jpg

early and aswin like this

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Looks like it is a brand-new IBC?  Congrats, Jeff!

We dont have these totes available anywhere near us.  What is available are those cheap and used ones without any original labels in them. 

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9 hours ago, vkn said:

Looks like it is a brand-new IBC?  Congrats, Jeff!

We dont have these totes available anywhere near us.  What is available are those cheap and used ones without any original labels in them. 

Actually, it's used but was fortunately quite clean. It originally contained a bactericidal solution comprised of formaldehyde, formic acid, and propionic acid which I decided would be okay since they are naturally occurring and breakdown readily. Anyone disagree? 

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6 hours ago, JeffH said:

Actually, it's used but was fortunately quite clean. It originally contained a bactericidal solution comprised of formaldehyde, formic acid, and propionic acid which I decided would be okay since they are naturally occurring and breakdown readily. Anyone disagree? 

I never used IBCs, one reason being new IBCs are unavailable in this part of the world.  In one of Friendly newsletters, this is what I had read on propionic acid and other chemicals.. Here is the link.  http://hosted.verticalresponse.com/527375/44b6f95427/1451002247/916695764b/

Cut/paste from them:

"Warning: the LDPE plastic that the totes is manufactured from is slightly porous; when a tote is used (even for a short period of time) to store something toxic, the toxic substance will leach into the LDPE, to leach out into your aquaponic system at some unspecified future time.

We've seen toxic results with totes used to store propionic acid (a food preservative that is used in animal food processing); and totes in which organophosphate insecticides or herbicides were stored or mixed "for a short time only" "

Imagine having a toxic tote in your system: maybe your fish and plants don't all die, or just a few of them. You may not be able to trace it back to the tote. In fact, you may not even notice the problem; but if you or someone else is eating the poisoned fish and vegetables that come from your system; what's your responsibility to them?

If you can read the label on the used tote you're thinking about buying, and you understand enough chemistry to know that it is a non-toxic substance for your fish and vegetables, then by all means go ahead and use it. That is, if you're absolutely certain it never had anything else in it, even for a short time.
 

This can be a problem, because many of the places (often farms or industrial processing facilities) that purchase innocuous things in IBC totes later use them for mixing non-innocuous things such as Roundup, Polyglyphosate, mildewcide, and other things that are serious central nervous-system disruptors for fish (and human beings!)
"

Over to you.  Let's also see what do others say?

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That seems pretty unlikely unless they didn't clean their IBC's prior to using them; IBC's are intended to be cleaned and re-used: Guidelines for the Reuse of Intermediate Bulk Containers

Even if they contained "acutely dangerous material" they are cleaned out and re-used.

Quote

By Law: If the emptied IBC had contained an Acutely Dangerous Material (P-listed and poisonous by inhalation), 40 CFR 261.31 shall apply as follows: The IBC must be triple rinsed, drip dry and certified to be in compliance.

 

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1 hour ago, DavidWI said:

That seems pretty unlikely unless they didn't clean their IBC's prior to using them; IBC's are intended to be cleaned and re-used: Guidelines for the Reuse of Intermediate Bulk Containers

Even if they contained "acutely dangerous material" they are cleaned out and re-used.

 

Thanks.  It is an eyeopener to me.. I was not aware of a big industry called  "Qualified IBC Reconditioners" and some employees are called 'hazmat employees'.  (For the uninformed, personnel handling IBCs that previously contained hazardous materials are “hazmat employees” and must be trained in accordance with DOT regulations.)

I checked several other reports today.. Here is an interesting one.  http://www.bucknerbarrel.com/pdfs/Agreement_Between_IBC_Reconditioners_and_Emptiers.pdf

Quote

Examples of materials not accepted by many IBC reconditioners: • Herbicides/some pesticides; • Biological agents; • Cyanides or Cyanide compounds; • Radioactive materials; • Dioxin; • PCBs • Packing Groups I and II poisons as well as Poison–Inhalation Hazards (PIH).

 I find this subject of IBC reuse all the more complicated.

Do ALL the used IBCs cleaned by these qualified 'recondioners of IBCs in the US from where it is exported to the other world (millions)?  Do they follow similar set of rules in India?  Do they tell or have product markings/labels of what is carried in the first use, second use, third use, etc.? Can we know if it is repaired, re-bottled, or re-manufactured or routinely maintained by the reconditioner?  Do they educate the users on the compliance/label marks?  

Some of my tribe often approach me with questions on using IBCs in India and I had discouraged many over years.  So I value your comment and I am genuinely interested in this subject with an intention to know more about this.

Several questions.  Any more inputs, appreciated!  Thanks in advance.

Request mods to move this to an appropriate thread for further discussion on this.

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Hi Vkn,

Thanks for the info, however, I'm a bit skeptical of newsletters and other anecdotal evidence for these types of issues. How do they explain, for example, that organic acids such as propionic acid have been used as feed additives for aquaponic (and other) systems (see http://www.aquafeed.com/documents/1216999805_1.pdf)?

Also, my IBC is made of type 2 (HDPE) plastic.

Agree though, that one needs to be careful about what else might have been stored in the containers.

Cheers,
Jeff

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8 hours ago, JeffH said:

Hi Vkn,

Thanks for the info, however, I'm a bit skeptical of newsletters and other anecdotal evidence for these types of issues. How do they explain, for example, that organic acids such as propionic acid have been used as feed additives for aquaponic (and other) systems (see http://www.aquafeed.com/documents/1216999805_1.pdf)?

Also, my IBC is made of type 2 (HDPE) plastic.

Agree though, that one needs to be careful about what else might have been stored in the containers.

Cheers,
Jeff

On propionic acid and other hazardous substances used in IBCs on resale, I am not convinced enough as we can see there are several conflicting reports.  Such as this one, http://www.sciencedirect.com/science/article/pii/S1388198110001678  So, I won't use it or recommend it to others until we have clear labels of its prior use (in India) and know that it is triple-cleaned, etc. by said professionals.

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Jeff, hope I have not scared you with this.  If it is HDPE and cleaned, it should be safe.  How is progress with your system build?

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No worries Vkn, this discussion is helpful in highlighting these types of issues where the answers aren't always clear. In any case, while I'm using the IBC for my prototype, my commercial system will use either concrete tanks (coated with something I have yet to determine!) or, more likely, wood frames lined with Ultra Skrim. I was impressed how the system that Jon Parr built for School Grown (schoolgrown.org) are so simple - just wooden frames made from 2x4s without any need for fully planked sides. The Ultra Skrim liner, if fitted with a slight curve along the bottom edges, does not exert the sideways pressure you might expect making the design of this type of grow bed amazingly simple. Anyway... that's all a ways off! 

Yesterday was sand day! I laboriously washed my sand 1/2 a bucket at a time and carried it around to my grow bed. Took me hours but finally got it done! The sand I was able to find is quite coarse, with a good percentage of grains larger than 2 mm but also has a lot of small stuff too. In other words, it's around the right range (perhaps on the larger side) and is not very even. I've included a photo below.

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As you can see from my previous post, I started some water flowing today! The return was a bit silty since my sand (kind of a contractor's coarse sand that is crushed river rock) had some silt. I did wash it as I mentioned but some silt remained. Not a lot though and after 30 minutes or so, the water was running clear. The two cups below show the initial return water and a sample taken after about 30 minutes. I wasn't expecting the water to run the length of the grow bed initially and that's what happened. The drainage appears to be excellent. 

30081111943_fec6de78a4_z.jpg

30598836812_c6be075e37_z.jpg

30678788856_df8a4b50ec_z.jpg

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VK (or anyone else!), I was wondering if you have any beds where the drain is a little higher than the bottom of the bed, meaning that some water would remain at the bottom between drain cycles. Mark warns against this on the iAVs site (potentially creating an anaerobic zone) but I wonder, with the frequent cycles whether this would actually happen. I ask because my drain is about 1 inch above the floor of the bed.

Also, my flow rate is much higher right now than the suggested 1/4 fish tank volume per cycle. Have you run beds with 2 or 3 times that volume per cycle? Thoughts?

Cheers,
Jeff

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1 hour ago, JeffH said:

VK (or anyone else!), I was wondering if you have any beds where the drain is a little higher than the bottom of the bed, meaning that some water would remain at the bottom between drain cycles. Mark warns against this on the iAVs site (potentially creating an anaerobic zone) but I wonder, with the frequent cycles whether this would actually happen. I ask because my drain is about 1 inch above the floor of the bed.

Also, my flow rate is much higher right now than the suggested 1/4 fish tank volume per cycle. Have you run beds with 2 or 3 times that volume per cycle? Thoughts?

Cheers,
Jeff

Never got a chance to see the effects of such a permanently saturated anaerobic zone but I would also suggest that such conditions should be strenuously avoided.

Higher flow rate/volume, that would add stress to the fish and they would not be happy if water levels go further down below 1/4th of the tank.

 

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Thanks VK,

Agreed about avoiding the saturated zone. I'm going to install a drain on the bottom of the grow bed today to address this issue. Regarding the higher flow rate, although the rate is higher than 1/4 tank, not all that water is pumped out of the fish tank at the same time because some is returning while the pump is on. I'll make a more accurate measurement today to see what percentage of the fish tank is in the bed at maximum saturation during the cycle.

Another thing I've been wondering about is something I read on Murray Hallam's site (http://aquaponics.net.au/forum/threads/flood-and-drain-v-continuous-flow.257/). He is talking about a flood and drain system and notes:

Bottom 50mm. This is the solids collection and mineralisation zone. By having 20mm gravel media the solids that are delivered from the fish tank on each flood and drain cycle, settle to the bottom of the grow bed and are there mineralised and broken down over time. This lowest layer suffers badly if the media used is too fine. Oxygen laden air and water are unable to travel freely through the grow bed if the media is too fine. This can result in dead spots which can go anaerobic.

I thought that was interesting since we are obviously using media much smaller than 20 mm. Why does iAVs not suffer from these "dead spots" that he mentions? My only guess is that since he is flooding from below, the solids might clog up a finer media whereas iAVs dumps them on the surface so that the water flowing through the bottom 50 mm is free of debris. This also suggests that mineralization in a "top flooded" system occurs at the surface, or at least near to it. Thoughts?

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30 minutes ago, JeffH said:

I thought that was interesting since we are obviously using media much smaller than 20 mm. Why does iAVs not suffer from these "dead spots" that he mentions? My only guess is that since he is flooding from below, the solids might clog up a finer media whereas iAVs dumps them on the surface so that the water flowing through the bottom 50 mm is free of debris. This also suggests that mineralization in a "top flooded" system occurs at the surface, or at least near to it. Thoughts?

You are correct, and this is part of what makes the sand bed work so well. Instead of a pile of muck in the bottom of a gravel bed, most of the solids are captured in the upper part of the sand, and only water and dissolved nutrients pass through and back to the fish tank.

IMO - Large aggregate flood and drain should not include solids in the grow bed; mineralization should be done before the water is sent to the plants, so the media remains open and oxygenated.  Large aggregates are used in hydroponic flood and drain as a support for plant roots because the nutrient can flow into and through the media and flow right back out again, and they can work the same way in aquaponics if there are no solids.

The filtration offered by gravel is mediocre at best, but solids will build up over time, as anyone using these systems can attest, making for an interesting mix of gravel and muck. Many people are growing in these gravel/muck buds, but conditions are hardly ideal for plant roots, and production suffers as a result.  I've yet to see any pictures or videos of aquaponic flood and drain gravel systems providing growth that would rival what I've seen in simple organic soil gardening. I'm not saying those systems don't exist, but I haven't seen them.

iAVs is basically an intermittent sand biofilter that we happen to be growing plants in, and the solids capture efficiency of sand is well documented.  Very few, if any, of those solids will make it to the bottom of the sand bed. The surface are provided by sand for biological activity far exceeds gravel for the same volume, and the coarseness of the ideal sand provides for thorough oxygenation of the root zone as the water drains. This allows aerobic organisms to break down the solids in the root zone, instead of leaving it to the anaerobic organisms to rot the muck at the bottom of the bed. The sand provides an environment that's actually better for the plants than regular soil, and production reflects this.

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Thanks MT, certainly makes sense to me. I'd love to see some comparisons of sand/small gravel sizes to see if bumping the grain size of the media to 3-4 mm would make a significant difference. I can already tell that solids wouldn't make it very far down the bed, but I imagine someone has looked at this. Know of any studies?

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Hi JeffH

Indeed it makes a significant difference.

cut/paste from this doc/pdf http://www.doh.wa.gov/portals/1/Documents/Pubs/337-104.pdf

Summary: This report summarizes the literature on the topic of specifications for media of sand-based on-sitewastewater treatment systems. The granular media must be coarse enough to permit a sufficient flowrate yet fine enough to provide adequate treatment. Media that is too coarse lowers the wastewater retention time to a point where treatment becomes inadequate. Media with small grain size slow the water movement and increase the chance of clogging. The effective size (D10) and uniformitycoefficient (Uc) are the principal characteristics of granular media treatment systems.

The ideal sand media for intermittent sand filters is a coarse sand with an effective size between 0.3 mm and 0.5 mm.

The media sand grains should be relatively uniform in size having a low Uc value (less than 4.0) to promote movement of water and prevent clogging.

There is loads of sientific studies on the topic

https://scholar.google.no/scholar?q=sandfilter+grain+size&hl=no&as_sdt=0&as_vis=1&oi=scholart&sa=X&ved=0ahUKEwiP_d7714rQAhXDDSwKHVFnDP8QgQMIGTAA

 

cheers

 

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Thanks Ande, a very useful doc! As you can see from my photos, the crushed rock I have varies a lot in size. The WA gov doc suggests that this is undesirable because smaller particles can fill the voids of larger ones and cause clogging. I'm hoping mine won't though because I have washed out the very fine stuff. I wish I had some grading sieves to see size percentages in my media. It's hard to tell by eye-balling it!

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I built a small iAVs system and sifted my own sand from a batch of "decomposed granite" by hand. I ended up with a mix that was larger than recommended, but still smaller than 3-4mm. I should have included smaller sand because the system drained to fast to work properly. Only by overloading the system with 50 goldfish being fed at 3%/day did it finally "flood" as intended, but I didn't have nearly enough plants to assimilate this much nutrient, so when the Nitrates got over 150 and stayed there, I started losing fish. Even then, I was using two pumps to get the necessary flow, which was way over the recommendation since they were cycling the 40-gallon fish tank twice in the 20 minute run time.

Even a seemingly small difference in sand size can make a significant difference in operation. I highly recommend looking for sand that matches the C33 standard, if you can. I know you're not in the states, but here is a copy of an older version of the standard; it should give you something to work from.

C-331.pdf

Edit: I just noticed that I had missed the pictures of your sand and drain water. I'm concerned about how much your sand will settle over time, specifically regarding smaller particles washing into the lower part of the media and creating a muddy bottom that doesn't drain, but as you said before - it's hard to tell by eyeballing it. Best of luck!

Edited by MT Mind (see edit history)
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MT, that drainage water is from the first 30 minutes. It runs clear now. Good question though, re whether the smaller particles will settle down to the bottom. 

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Hi MT, I was curious about your note above about having to overload your fish tank in order for the system to flood properly. I am interpreting this to mean that without the extra waste being deposited on the grow bed, the water was making it all the way down the furrows because it would seep through too quickly? If this is the case, do you think it would have corrected itself once some biofilm built up on the furrows?

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A question for iAVs-ers

Could an iAVs bed act as a solids and fines biofilter for a DWC system? I have been wondering if you could simply have an iAVs bed with perhaps a few plants, but definitely not enough to take up all the nutrients. Could the water then flow to a DWC bed for growing other crops? It seems like the iAVs bed does essentially what many DWC filter systems do. Would the sand hold back essential nutrients for the DWC section or would the water from the iAVs growbed contain enough?

Yes, I want the best of both worlds... :-)

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