Air Lift Part Two. 

I had, what my 10 year old would call and "epic fail" with the air lift. I consulted many articles and papers of the scientific variety before building my pump. I did not however refer to any Internet resources about people who had actually built them. Big reminder of theoretic construction and operation and real world construction and operation. Within about 2 minutes of looking online at folks who had built air lifts, I could see what my issues were. Maybe try again next week.

Air Lift Pump. 

This weekend I am building an air lift pump prototype. An air lift pump uses and small air compressor to aerate water that is going into a vertical pipe. The aerated water is less dense than the water above it in the pipe and moves upward while pushing the water above it up as well. The constant stream of bubble / water mixture continues to push water up the pipe until it flows from the top of the pipe which can be pretty tall according to the papers I have been reading. The reasons for using the air lift are for energy conservation. While planning my large aquaponic setup, I am planning on everything running on stored solar power. There is a large difference in how much power an air bubbler uses vs. a water pump. Now the question that the prototype will answer is how efficient is it. I want to know how much water can I move for a unit of energy with a pump vs. an air lift. My materials for this prototype are:

3/4 PVC

Some 90 degree elbows.

A couple of 3/4 caps

My dremel

A couple of tiny, and I mean tiny, drill bits

Something that blows air. Not me. That air is too hot.

The Bell Siphon. 

I want to discuss the construction, use and operation of the bell siphon or what some people call the auto siphon. The bell siphon is the secret to how an ebb and flow system works. The ebb and flow system allows the grow bed to be flooded, then drains the water down to the bottom. You can imagine a complicated array of timers, sensors, servos and valves to do this job, but really all you need is a water pump and a bell siphon. Here is a bad drawing of how it works.

We can see in figure 1a without a bell siphon, that the water is pumped up from the fish bed (not shown) into the grow bed. As the water fills the bed, it eventually becomes level with the standpipe and starts to drain back to the fish. the water flow is shown in red arrows. This method is great if we want to maintain an exact water level in the bed. The water will not get higher than the height of the standpipe. You can use this application in a fish bed that you do not want to overflow because of rain. As the rain fills your fish bed, the standpipe would keep the level the same as it was before it started raining. For our grow bed, however, we want the water to fill the bed then drain away almost completely. We want our roots soaked often with nutrient rich water from the fish bed, but we don't want them setting in water all the time. You can see from Figure 1b that with the bell siphon, water rises inside the siphon body until it reaches the standpipe height and then starts to drain. As the water drains, it builds up back pressure and creates a vacuum. Very quickly the vacuum outpaces the amount of water flowing into the system from the fish, and it drains the grow bed down to the bottom. Once air enters the siphon from the bottom, the suction is broken, and the bed starts to fill again. Over and over, it fills and drains, and no timers or controllers are needed. I hope that is a clear explanation on the operation of the bell siphon. Here is a video of one of mine working:

As you can see, the water level reaches a certain height and the pressure builds until the suction kicks in and then SLURP, all gone. To me it is just cool.

Now with a bell siphon it is all about water flow in vs. water flow out. It is a somewhat delicate balance. It really has to do with how much water is flowing into your system and the pipe sizes for draining that flow. You need enough water to flow over the standpipe to create the vacuum but it needs to be slow enough to let the bed almost completely drain and allow the vacuum to be broken by letting air enter the siphon. I will discuss how to manage the balance in the bell siphon build post next.

To build a bell siphon you need to answer a few questions first. Mostly you need to know how large of a grow bed are you going to fill and drain. This will determine what size pipes you will use. My experimental setup is very small but I use 1" PVC to drain it. At this point I want to link a document that helped me immensely. The paper is by the College of Tropical Agriculture and Human Resources in Hawaii and is about bell siphons. I am not sure about linking here but hopefully this does not violate any copyright stuff. Great paper and I used it over and over while building my first couple of siphons:

http://www.ctahr.hawaii.edu/oc/freepubs/pdf/BIO-10.pdf

This paper describes the ratio between standpipe and bell siphon diameter. I found some very scientific analysis of the ratios in other published works, but prefer the method described in the paper above, where by you just double the diameter from standpipe to bell siphon to debris guard. So have used 1" for the standpipe, 2" for the bell siphon, and 4" PVC for the debris guard. 

To build the bell siphon you will need:

Materials:

2" PVC pipe

1" PVC pipe

2" PVC cap

100% silicone

Large zip tie

1/4" lead hose

PVC primer and cement

Tools:

Hacksaw

Dremel

Drill

1/4" drill bit

Pliers

Ruler

Pencil

To make the bell siphon, we are going to start with some measurements. We want the top of the standpipe to be below the rock or media in the grow bed. I found out the hard way that if your water comes over the grow media, and you get a nice sunny day, you will very efficiently grow algae, that will then be sucked down into the fish bed (see my earlier posts about my algae bloom). So I measure a rough estimate as to how full this grow bed will be and then figure out a height of the stand pipe. In this case I figured 6 inches. 

Next, I put the 2" PVC cap on the 2" inch piece of pipe and draw a circle under the lip of the cap. This is the guide as to where the top of the standpipe should end up. The paper by the College of Tropical Agriculture and Human Resources linked above states that the top of the standpipe must be flush with the bottom of the cap. This makes a bit of guessing as the cap slides down the 2" pipe quite a bit.

My solution for this calculation is to take a piece of 1" pipe and mark it the height that the standpipe will be, in this case 6". Now place the 2" pipe that will be the bell siphon body next to the 1" pipe and line the 1" pipe end up to the pencil ring that shows where the cap seated to. Mark the 2" pipe using the mark on the 1" pipe. This should give you the right length of bell siphon pipe to leave the standpipe at the same height as the bottom of the cap.

 Now cut the 2" pipe to size. I like a hacksaw for its accuracy and speed but you can use whatever you like. My first models I used a Dremel with the cutting wheel and just worked it around the pipe, but it always ended up uneven. Remember to use a medium grit sandpaper on the cut end to remove PVC shavings. I sand outside, then bottom edge then inside by wrapping the sandpaper around my finger.

Now you must make the intake ports on the bottom of the bell siphon. This is where water will fill the siphon at first until the pressure builds and then this is where water will be sucked through as the vacuum increases. There is some science as to size and flow rates, but I have just gone with 4 ports that are 1/2 inch by 1/2 inch. I use my Dremel to make 1/2 inch slices into the bottom of the pipe. You could use a hacksaw across the bottom as well. I just hack into the bottom with enough cuts so I can break the "teeth" out with my pliers.

Multiple cuts into the bottom of the bell siphon.

Snap the "teeth" out of the cuts to make your ports.

Next you will attach your snorkel. I have used 1/4" lead free hose. I bought a bit of it from Lowes as you can see from the photo. I was using this hose and some 1" lead free for a beer making project so I had some extra on hand. Find a drill bit that is a bit smaller than the hose. I find using a bit that is the same size as the  inside diameter of the hose works great as the outside diameter is larger and makes a good starting seal.

Drill a hole into the side of the 2" PVC cap and fit it to the 2" pipe. 

Give it a test to make sure the hose fits well in the hole you made.

Don't worry if the pipe and cap overlap in the hole, just drill again into the same hole and clear the pipe and hole. 

Once you are satisfied with the fit of everything, use the purple primer and PVC cement to put the cap on. You have to move quickly to line up the holes and remember, if you miss a little, no problem just gently re-drill the hole to remove any pipe that is blocking your way.

Here is you bell siphon so far.

Now you want to insert the hose into the hole you drilled. It only needs to go in a short way. Since you made the hole the same diameter as the inside of the hose, you will have to wiggle it a bit to get it in. After you have fitted the hose in place, seal it up with 100% silicone. The picture shows me using the silicone gun directly to the hose, but I found that if you put on some nitrile gloves and squirt some silicone on your finger, you can make this seal much neater and more effective.

I added a bead of silicone to the hose and wrapped some wire around it to hold it while it dried. This was no substitute for a zip tie around the snorkel, but it did offer some extra support.

Add a zip tie around the snorkel and the bell siphon to hold the snorkel in place and clip the snorkel hose. 

When you are going to snip the hose, remember that this will determine the height that your water will drain to. Once air enters the snorkel, the vacuum will be lost and the bell siphon will stop draining until it fills back up again. I have always cut my snorkel about an 1/8 of and inch above the intake ports. This means you will leave about 3/4 of an inch of water in your grow bed after it is drained. If you are using a shallow grow bed you may have to get more precise about the amount of water left in the system when it is in the drained state.

The next section will discuss adding the Grow bed to the table, and adding the piping. In that section we will talk about tuning the bell siphon to the water flow to get good consistent fills and drains. 

Please drop me a line if I can answer any questions about this process. 

Clear Water Again.

Well the fish bed is crystal clear again and the fish are much more active, at least I can see that they are more active. I added a bin above the grow bed to raise a little duck weed. I was hoping that this would filter out a lot of the algae that bloomed last week. So far it has done pretty well, but I don't think the plants I put in are duckweed. They are strung together on a soft stem and have roots. I will have to look into this further. Here is a picture of the duckweed bed.

Below is a picture of my fish bed before I starting the filtering process.

And here it is after. The duckweed container has a standpipe that empties into the grow bed below it. The standpipe seems to help with the algae issue too. I am also using a bio filter mat under the standpipe from teh duckweed bin to collect solids. 

This week will be an experiment in duckweed growth and keeping algae from growing in the duckweed bin as it will be in the direct sunlight all day. I also need to find a source in Mobile for some duckweed. 

This is as example of the plant I picked up at Langam Park... Shhh don't tell. It was in a still pool not connected to the lake, but standing water off by itself. Duckweed looks like it is individual leaf clusters so I am thinking this is not it. If anyone knows where to find duckweed in Mobile, please let me know.

Larger picture of the complete system as it sits now with added duckweed bin.

Algae!

I have noticed my water getting greener and greener over the last couple of days. I figured out that two things are to blame for this algae bloom. 1st, my new bell siphon and standpipe allowed the water to rise above the grow medium for a short while. This short time above the grow rocks in the direct sunlight was enough to start the bloom. Also as the summer is fading, the sunlight started slanting in under my table, exposing the fish bed to direct sunlight. Argh. Thick green water is the result. I put a temp curtain up to block the sun and modified the bell siphon so all feed water stays below the rocks. Hoping it works.

Ugly green water. The algae eater must by in heaven.

Temp curtain until this weekend when a permanent solution can be installed.

Adding in a few more fish.

I added three more Koi and an algae eater or Plecostomus to the fish tank on the table system. The three Koi  that I originally had in there were not producing enough ammonia or nitrites to really add a lot of nitrogen to the plant bed. I am hoping the additional fish will raise these levels. I bought Wal-Mart fish and was surprised by the price. The Koi cost about 6 dollars a piece. Since this is an experimental system, I thought using Koi would be a smart alternative to Tilapia which is what I plan to raise in later systems, but Tilapia is actually cheaper if you buy fingerlings and buy 25 or more. My fish container is 4.5 cubic feet which equated to about 33.5 gallons. At 1 half of a pound of fish per gallon and Tilapia final weights being 1 and 1 half pounds, I should be able to put around twenty Tilapia in the fish area. 

Aquaponics Table Build Part 1

Preparing the table and Grow Bed

In this post I want to cover how to prepare a table and the grow bed for your backyard Aquaponics system. Pictured below is a rough table I built for this purpose. It is just a lumber table that I screwed together. It is made with 2x4's and 3/4 inch ply for the top. The table must be sturdy becaus the weight of the grow media is very high, also you will be filling the grow bed up with water over and over all day. It has to stand up to a lot of weight and constantly changing weights. To work on this portion of the project you will need the following:

Sturdy Table you don't mind drilling holes in.

Rotary Tool (like a Dremel) with a basic set of attachments.

Plastic bin for a grow bed.

Small piece of 3/4" PVC pipe. We will use a section of 3/4" for some of the plumbing. Cut a small piece off for a quick measuring guide.

Small piece of 4" PVC pipe. Same as above. You need about 8 inches total, and can cut a small piece for measuring.

Drill

1" paddle bit

3/4" paddle bit

3/4" PVC slip to threaded adapter

3/4" threaded to 1/2" rubber hose adapter

Prepare the holes:

My grow bed is a Rubbermaid, 31 quart clear bin. I bought it at Lowe's for about 5 bucks. I like the clear containers fro grow beds because you can see the water levels in the bed and keep track of your root growth as your plants take off. You can also see when you start to build up the bacteria and algae that is beneficial to you plants. This system has the PVC piping coming through the table and into the grow bed. My last design drained through the paper slot on an old printer table and fed fish water up and over the lip of the bed. This time I am going to have the feed water come up through the bottom. I think this will be better because the feed pipe will work as a drain when the flow stops. To get this right, I put the bin on the table and figured out where my siphon and feed pipe would be. Keep in mind that I am using 3/4 inch PVC for the feed pipe and the siphon will be surrounded by a 4" PVC sleeve. I cut small pieces of these PVC pipes to work on the placement.

After you find a good placement for the 1" drain pipe and the 3/4 inch fill pipe. Use the Dremel to grind through the bin and put a pretty good divot in the table. You will use these marks to make your holes. I used the 1" paddle bit and drilled a hole through the table using the divot as a guide. 

Then I centered the pipe over the hole and traced it. Remember that the 1" paddle bit makes a 1" hole, but the diameter of the outside of the pipe is a bit bigger.

I used the sanding attachment on the Dremel to slowly open the hole to fit the pipe. I wanted a very tight fit to prevent leaking and to support the pipe once I inserted it, so I went very slow and tried to put the pipe in several times. I do the same process for the 3/4" feed pipe using a 3/4" paddle bit and then slowly expanding the hole.

Once you have a tight fit, you can leave the pipe in and move on to the next step which is figuring out how high your stand pipe will have to be.

Now for a quick explanation of what the standpipe is going to do for us. It will keep the water level limited to a certain height. we need to figure out what height that will be. Usually about an inch below the top of the bin. Below is a bad drawing I did of a stand pipe that explains more about how it works.

From here you can see that as the water level goes over the height of the stand pipe, it will drain out of the bottom and keep the water level limited to that height. Now, for the plants in our bed, we want to soak the roots very well with the waste water before we drain so we will add another part to the stand pipe that will allow the water to reach the standpipe height then be drained down to empty again. That part is the bell siphon and we will build it during the next part.

Take an eyeball on the height about 1 inch below the lip. Another good reason to have a clear grow bed. Make a note of the height as we will need it for the next part. I hope this was easy to follow. If you have any questions, please comment below and I will respond as best as possible.