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  • A 4-Step Sand Test Rig

    In an attempt to expand the iAVs knowledge base, we need to answer some questions about sand that falls outside of the current iAVs-suitable specification.

    In the Sandponics Sandpit thread, I wrote:

    "Sand is central to iAVs...and iAVs-suitable sand is clearly described. It's inert, free of silt and clay and consists of a mix of particle sizes that, in the stated proportions, afforded (very) adequate drainage. Mark can speak with authority about sand of this specification. It's what he used...it produced validated outcomes...it works...and, if you source sand of the same specification, it will allow you to achieve similar (if not better) results."

    But what if the proportions vary from those stipulated in the specification? What if there's more fine sand? We know that the greater the fine sand fraction, the greater the likelihood that drainage will be impaired. What happens if there's more sand at the 1mm - 2mm end of the range? We know that, if the sand mix is too coarse, we'll struggle to flood the furrows effectively. But how much is too much? Can we accommodate some variations in sand fractionation by changing our operating regime.

    The fact is that, without testing, we simply don't know.

    Mark has proposed a 4-Step process to test sand that falls outside of the current iAVs-suitable specification.
    1. Physical properties of sand
    2. Plant impacts – using water-soluble nutrients
    3. Development of Soil Microbiology – using fish feed.
    4. Adaptation for fish
    ...that allows us to select a particular sand fractionation and then determine its physical properties including hydraulic conductivity. In Step 2, we introduce plants and see how they are impacted by the physical properties of the sand...using water-soluble nutrients. Step 3 sees the development of Soil Microbiology using fish feed as the organic input. Once we've established that the sand is fit for purpose, we are able to proceed to Step 4...and introduce fish into the equation.

    I'm excited by this development because it enables us to learn everything we need to know about the sand that is available to us...on a desktop scale...before we commit to the construction of a larger system.

    The other thing that grabs me is that, even where the sand sample proves to be less than ideal...or even problematic...we'll have the opportunity to see whether we can address its shortcomings by manipulating the operating parameters.

    In this thread, we'll build the test rig and we'll set out to resolve the unanswered questions that exist around sand.
    "All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident." - Arthur Schopenhauer

    www.garydonaldson.net - my main website.

    https://www.facebook.com/gary.donaldson.161 - my Facebook page.

    https://www.facebook.com/groups/1167267703372756/ - my Microponics and Waste Transformation Farming Facebook Group

    https://www.facebook.com/groups/1318946951452383/ - my iAVs Facebook Group

    www.urbanaquaponics.com.au - the current home of the Online Urban Aquaponics Manual.

  • #2
    Very interested in this conversation. Are there any non negotiable parameters? I would imagine pH inertness is one. Unless the source nutrients are acidic enough to offset the alkalinity of carbonates rich sand. The only example I can think of is organic materials pretreated by fermentation. But that would preclude the use of fish.

    I have frequently wondered if a coarser sand might be viable if a thin layer of fine sand were used at surface to maintain the filtering at surface property. What you'd then be testing is the impact of higher hydraulic conductivity and lowered surface area... I'd speculate that biolfilm might fill a lot of the additional pore space and diminish the apparent missing surface area somewhat. Pure speculation though.

    Comment


    • #3
      As long as the proponent of an idea is willing to test it...and then report on the test method and results...I don't personally regard anything as being non-negotiable. We came up with the notion of Sandponics to allow discussion of sand-related ideas without any potential for it to impact iAVs' lineage...and without having to experience the frustration that comes from people proposing improvements to iAVs without ever having built the real deal much less exposing it to objective comparison. We can now remain detached...and the focus shifts from being a prescriptive one to being a facilitative one.

      We want people to help us expand the knowledge base around sand...but our main motivation is to empower them...to thelp them better understand the medium - and to source sand - and a plant production regime - that works for them. Our end goal is to help people put clean fresh food on the table.

      Of course, if someone wants to push an idea, without being prepared to test it, they're probably going to be reminded that an untested idea is almost worthless. We're hoping that, over time, the people who are actively engaged in Sandponics will manage that side of things...politely reminding people of how the idea generation/idea testing/results reporting process looks like.

      Part of the process of encouraging the exploration of new ideas is about providing a methodology for that to occur - and that's why we're talking about a test rig and the 4-Step process. We're not saying that people have to use that process...we're simply making it available for them to use - if they think it might be helpful.
      "All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident." - Arthur Schopenhauer

      www.garydonaldson.net - my main website.

      https://www.facebook.com/gary.donaldson.161 - my Facebook page.

      https://www.facebook.com/groups/1167267703372756/ - my Microponics and Waste Transformation Farming Facebook Group

      https://www.facebook.com/groups/1318946951452383/ - my iAVs Facebook Group

      www.urbanaquaponics.com.au - the current home of the Online Urban Aquaponics Manual.

      Comment


      • #4

        Originally posted by Shadders View Post
        I would imagine pH inertness is one. Unless the source nutrients are acidic enough to offset the alkalinity of carbonates rich sand. The only example I can think of is organic materials pretreated by fermentation. But that would preclude the use of fish.

        I have frequently wondered if a coarser sand might be viable if a thin layer of fine sand were used at surface to maintain the filtering at surface property. What you'd then be testing is the impact of higher hydraulic conductivity and lowered surface area... I'd speculate that biolfilm might fill a lot of the additional pore space and diminish the apparent missing surface area somewhat. Pure speculation though.
        The focus of Sandponics...and particularly the Sandpit...is not what can - or can not - be discussed, but rather what works. The question is not whether experimentation around pH should be entertained but rather how plants are affected by pH outside the recommended range...and how that impacts the operator's personal food production goals.

        If the operator is engaged in commercial food production...and their goal is profitability arising from growing the best (most marketable) plants in the shortest possible time at the lowest possible cost...then strict adherence to the recommended pH range is a no-brainer. If, however, the operator's goal is to put clean fresh food on their table, there may be scope for some wiggle room around pH.

        Like everything else that fall outside of clearly defined parameters, the impact of pH variations can only be determined through testing. Once you know the impact of high pH on your plants, you are able to make informed decisions about whether that deviation from best practice (ie...the recommened pH range) is sustainable in your circumstances or not.
        "All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident." - Arthur Schopenhauer

        www.garydonaldson.net - my main website.

        https://www.facebook.com/gary.donaldson.161 - my Facebook page.

        https://www.facebook.com/groups/1167267703372756/ - my Microponics and Waste Transformation Farming Facebook Group

        https://www.facebook.com/groups/1318946951452383/ - my iAVs Facebook Group

        www.urbanaquaponics.com.au - the current home of the Online Urban Aquaponics Manual.

        Comment


        • #5
          We've decided to base the test rig on 20 litre (5 gallon) plastic buckets. Each rig will consist of two such buckets....one to contain the sand and the other to function as a water reservoir. We chose the buckets because they remain relatively portable when full of sand or water, their depth approximates that of an iAVs sand biofilter and they are large enough to support a plant. Each rig will be fitted with its own small water pump and timer.

          I plan to set up four such test rigs so that I can test four sand samples simultaneously.

          Yesterday, I bought the buckets...and I have four different types of sand to test. I have yet to acquire the pumps and timers.

          While I'm waiting for those to arrive, I'll undertake the vinegar, pH and turbidity tests...and establish the pore space volume and hydraulic conductivity...for each sample.
          "All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident." - Arthur Schopenhauer

          www.garydonaldson.net - my main website.

          https://www.facebook.com/gary.donaldson.161 - my Facebook page.

          https://www.facebook.com/groups/1167267703372756/ - my Microponics and Waste Transformation Farming Facebook Group

          https://www.facebook.com/groups/1318946951452383/ - my iAVs Facebook Group

          www.urbanaquaponics.com.au - the current home of the Online Urban Aquaponics Manual.

          Comment


          • #6
            HOW ABOUT USING SAND MADE OUT OF ROCK.HERE IN INDIA IT IS VERY DIFFICULT TO GET RIVER SAND. SO IS IT POSSIBLE TO USE ROCK SAND .ANY BODY TRIED?/

            Comment


            • #7
              Hi kondath
              iAvs is spesifically pointing out crushed granite and/or quartz.
              From here http://iavs.info/how-to/sand-selection-guide/
              quote : " When we refer to sand for use in an iAVs biofilter/sand bed, we mean inert silica (SiO2) sand "

              cheers

              Comment


              • #8
                halo sir,
                how about using cocopeat instead of sand? any body tried? will it do the biofilteration needed for the iAVS

                cheers

                Comment


                • #9
                  Originally posted by kondath View Post
                  halo sir,
                  how about using cocopeat instead of sand? any body tried? will it do the biofilteration needed for the iAVS

                  cheers
                  1. iAVs was explicitly developed for application in arid regions such as in and around deserts where sand is abundant and virtually free. And where water is scarce/valuable and therefor many foods crops are not possible to cultivate by conventional methods in such regions. That it is now being adopted by relatively affluent western suburbanites was never anticipated - nor was its continuing absence from where intended/needed.
                  2. Sand is physically stable (does not decompose) so it does not need be replaced. Peat(s) do decompose, which is also an acidifying process.
                  3. Cost ... and its relative abundance globally (contrary to some counter assertion).
                  4. Sand is known as a historically viable media for use in vegetable cultivation and it is simultaneously maximally effective at particulate removal from water. No natural material outperforms sand for filtration - or even close.
                  5. Sand won’t water-log (assuming it is allowed to drain) and so it can easily be flood irrigated MANY times/day without ‘drowning’ plants. Peat retains moisture and couldn’t ‘handle’ the multiple complete tank exchanges per day - at least for very long - since it compacts as it rots.
                  6. A well drained sand has abundant Oxygen availability which is vital to all soil microbiology and plant root systems. Coir might initially but not for very long and probably not as well distributed nor recharged as with sand.
                  7. Sand can/does provide a solid surface for microbial attachment (biofilms).
                  8. given a bit of effort I could probably come up with several more reasons why sand is the filter and plant media of choice.

                  Nothing is preventing anyone from doing whatever it is they feel like doing, but without sand it's not iAVs. I also can't and won't suggest anything to anyone that I don't know for a fact on a personal level.
                  "There are in fact two things, science and opinion: the former begets knowledge, the latter ignorance." ~ Hippocrates, "Law", 400 BCE

                  Comment


                  • #10
                    Regarding the Sand Test Rig...I hope to have the first one built within the next couple of days. I've purchased enough components to enable me to have four of these test rigs operating - so that we can test four sand samples concurrently.
                    "All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident." - Arthur Schopenhauer

                    www.garydonaldson.net - my main website.

                    https://www.facebook.com/gary.donaldson.161 - my Facebook page.

                    https://www.facebook.com/groups/1167267703372756/ - my Microponics and Waste Transformation Farming Facebook Group

                    https://www.facebook.com/groups/1318946951452383/ - my iAVs Facebook Group

                    www.urbanaquaponics.com.au - the current home of the Online Urban Aquaponics Manual.

                    Comment


                    • #11
                      waiting to hear the results.let us know what sand used its diamensions etc

                      Comment


                      • #12

                        The sand test rig is finally a reality.

                        Each rig consists of a 20 litre (5 gallon) plastic bucket that will function as a water reservoir and a second one that will contain the sand being tested. I have created four test rigs to enable me to test 4 sand samples at the same time.

                        The sand bucket has 16 drain holes (4mm - 3/16") drilled around the base. The bucket is sat on two fired clay bricks inside of a black plastic tray. The tray has a hole drilled 12mm from the base and functions as a sand trap for any media that escapes the sand bucket. The tray drains into the water reservoir.

                        A small submersible pond pump is placed in the water reservoir. It has a capacity of 550 litres per hour (at zero head) and is fitted with a bypass device so the outflow can be regulated.

                        I've created a simple manifold from 20mm (3/4") poly tube - with a series of 6mm (1/4") holes punched in it - that serves to distribute the water from the pump around the circumference of the bucket.

                        The water will be pumped from the water reservoir up to the top of the sand bucket. It will percolate down through the sand and drain - from the holes in the base of the sand bucket - into the black tray and then eventually back into the bucket.
                        "All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident." - Arthur Schopenhauer

                        www.garydonaldson.net - my main website.

                        https://www.facebook.com/gary.donaldson.161 - my Facebook page.

                        https://www.facebook.com/groups/1167267703372756/ - my Microponics and Waste Transformation Farming Facebook Group

                        https://www.facebook.com/groups/1318946951452383/ - my iAVs Facebook Group

                        www.urbanaquaponics.com.au - the current home of the Online Urban Aquaponics Manual.

                        Comment


                        • #13
                          ...and here's the remaining images from the last post.
                          "All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident." - Arthur Schopenhauer

                          www.garydonaldson.net - my main website.

                          https://www.facebook.com/gary.donaldson.161 - my Facebook page.

                          https://www.facebook.com/groups/1167267703372756/ - my Microponics and Waste Transformation Farming Facebook Group

                          https://www.facebook.com/groups/1318946951452383/ - my iAVs Facebook Group

                          www.urbanaquaponics.com.au - the current home of the Online Urban Aquaponics Manual.

                          Comment


                          • #14
                            Gary,
                            Looks great! Looking forward to the future posts of script and data! Very nice

                            Comment


                            • #15
                              OK...before we launch into the sand testing, let's review a few things.

                              iAVs-suitable sand should be:
                              • inert - not chemically reactive when mixed with water.
                              • relatively free of silt and clay
                              • able to drain effectively...with sand fractionation within a known range of particle sizes.
                              iAVs-suitable sand is a known quantity...and, used in the method described by Mark McMurtry, it produced outcomes that were documented, validated, published and peer reviewed. For those who can access this sand, the pathway to the construction of an iAVs is very straightforward.

                              The Problem

                              People have reported difficulty in locating iAVs-suitable sand.

                              Establishing that the sand is inert is as easy as a simple vinegar test...and a pH test. A turbidity test will establish if the sand contains silt or clay...and leaving the same to settle will actually show the relative proportions of either silt or clay. So, that's easy, too.

                              It seems, however, that few sand vendors actually know the particle size range of their product...and, without guidance from them, prospective purchasers have little chance of determining that it is within the specified sand fractionation of iAVs.

                              So, to be able to source the correct sand, you (the users) have to not only know the iAVs sand fractionation, but you have to have a means of determining that the sand that you can access fits within that range.

                              And that's not the only issue. Let's assume, for example, that we were able to access the sand fractionation information that we needed...but the sand that you can access is different to that stipulated for iAVs. Maybe it had more fine material....or more coarse particles.

                              Is there any wiggle room around the iAVs specification? Could we stil use sand with some finer (or some coarser) material? Will that work? How well?

                              The simple fact is that we don't really know. The other simple fact is that we're never going to really know unless we test the sand.

                              A Different Approach

                              Now, we can get into the realm of sand fractionation testing...using expensive little gadgets that allow us to sort a sand sample into its various particle size fractions...or we could send our samples off to a materials testing laboratory to get them tested.

                              Or we could just ignore the whole sand fractionation thing....and apply the Sandponics approach.

                              Sandponics takes a different tack...one that has no interest in knowing the particle size range of a given sample of sand.

                              The only question addressed by Sandponics, in terms of a given sand sample, is not...'Is it iAVs-suitable?'...but rather...'Will it work for you?'...in an integrated aquaculture context.

                              Let me explain.

                              We know what works from an iAVs perspective. It's sand of a particular specification...and an operating framework comprising feeding rates, furrows and an intermittent irrigation events of a specific timing and duration. If you follow that prescription, you will get the same results that Mark got (or better)...and you will live happily ever after.

                              What we don't know is what the upper and lower limits of sand particle size are...when it comes to successfully growing plants with sand using the metabolic wastes of fish. One of the things that we hope to achieve with Sandponics is identify a wider range of suitable sands and, even where a particular sand sample proves to be marginal, to establish whether the irrigation regime might be adjusted to enable its use...while still ensuring adequate water quality for the fish.

                              The Sand Testing Process

                              The Sand Test Rig is the means by which users can identify sand that is suitable for use in integrated aquaculture.

                              it was described in detail in my previous post.

                              In my next post, I'll identify four sand samples....and conduct pH, Carbonate, turbidity, differential settling and pore space volume tests. Having recorded the results of these tests, I'll then move on to the hydraulic conductivity (drainage effectiveness) tests...and that's where the sand test rigs come into play.
                              "All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident." - Arthur Schopenhauer

                              www.garydonaldson.net - my main website.

                              https://www.facebook.com/gary.donaldson.161 - my Facebook page.

                              https://www.facebook.com/groups/1167267703372756/ - my Microponics and Waste Transformation Farming Facebook Group

                              https://www.facebook.com/groups/1318946951452383/ - my iAVs Facebook Group

                              www.urbanaquaponics.com.au - the current home of the Online Urban Aquaponics Manual.

                              Comment

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