So in my last post, I started describing the basics of controlling the flow of water in a complex aquaponics system. Here are some other constraints that I will be adding to my design.
- The design must get the best “bang” for the buck.
For the most part, I’m going to try to use inexpensive materials that are easy for me to acquire locally. For example, I don’t mind putting extra effort into cleaning up used IBCs if doing so saves a lot of money. As always, I’ll try to gauge my time against the cost of the item.
- The design must be power efficient
To accomplish this, I’ll be using a very efficient water pump that is always on. I am planning on using only one, high rate of flow pump. While it is possible to use several smaller pumps to more easily move the water around the system, this isn’t very efficient, and could lead to multiple points of failure. It is also possible to cycle the power on a pump to increase power efficiency, but in doing so the lifespan of the pump suffers. More reliable pumps and “soft start” pump controllers are more expensive. There may come a time when I rethink cycling the power on pumps, but first I’ll design a system that doesn’t require this.
- Shorter amounts of PVC pipe
The water will come into my system through city water, and it will either leave my aquaponics system through the city sewer, or be diverted to my lawn, flower beds and garden. I would prefer any water leaving the system go to my lawn or garden, but there may be times that I will want the used water to go directly to the city sewage treatment. I see this as several different PVC systems that include, 1) water delivery from the city to the system. 2) Water flushed from the system to the city sewer or to storage for lawn / garden. 3) Water delivered from the sump to the grow beds and to the fish tanks. 4) Water returning from the grow beds and fish tank to the sump.
I may make use of bridge siphons to connect parts of the system, and I will use flow restrictors for things like hanging towers of strawberries.
- Parts are easy to repair or replace
This means that anyplace I add a valve, pump, or other PVC connection, it should be installed in a manner that is easy to disconnect and replace with a new part. Valves should be easily repaired with standard tools.
- System must “fail safe”
If power goes out or the pump fails then the system should not flood at any point. Grow beds should drain completely, and fish tanks should stay full. If any valve fails in the open, or closed, position then the system must alarm, and the system must not lose water. There should be hooks built in for monitoring water levels and flow rate.
- System is easy to expand
If I want to add grow beds, fish tanks or sump tanks, it should only be a matter of space and a little extra plumbing.
- System is easy to clean
Solid waste should usually fall to an easily collected place. A standard pond vacuum cleaner should be able to reach all parts of the fish tanks. Grow beds should be easy to clean. This isn’t about bio filtration of waste – not yet.
Constraints are key to system design
I’ve read that any problem is easy to solve if there are no constraints to worry about. Sending a man to the Moon is relatively cheap and easy if you’re not worried about food, water, air, or an eventual return to Earth. It is constraints like this that define the challenge. And stating them clearly is a good way to start.
What must be understood is that at the start of a project, we really do not know what all the constraints might be. So I’ll be prepared to update this list.
In my last post, I’ve said that I want a project that helps me control an aquaponics system. These are both very vague goals, and I need to narrow them down, and then I need to figure out how to do them. It seems a bit silly to use Project Management Processes and Product-Oriented Processes to define and control my project when I am simultaneously the management, employee, and customer. However, it is still useful for me to define the project in these terms in order to create a timeline, benchmarks, and goal.
To start this I’ll first define what sort of aquaponics system I want to control, and speak about the constraints I must follow. As an aside, I’ve heard it said in many different contexts that any problem is easily solved if you do not have to worry about constraints. Even sending humans to Mars becomes much easier if you don’t have to worry about them arriving alive – or ever departing again! A round trip to Mars with living humans is considered a “constraint”.
What is an aquaponics system?
Aquaculture is the raising of fish (or other aquatic animals) for food. Such a system requires food and clean water, and the wastes from the system must be filtered out of it and disposed of, or else the system will become deadly to its animals. Hydroponics is the growing of plants in water for food. This sort of system requires that the water be fertilized and filtered, and watched for build-ups of waste and metals, or else the plants will die.
Aquaponics is a combination of these two methods of growing food, such that the wastes of the aquatic animals are used as fertilizer for the plants, and the plants clean the water for the animals. There is also a layer of nitrification bacteria in the system that break down ammonia and nitrates into nutrients for the plants.
In a perfect aquaponics system, you put fish food into the system, and you get meat and plants out of the system. Having said that, no aquaponics system is perfect, and a certain amount of tweaking the system is necessary.
To the right is a good example of a very simple aquaponics system. This system uses a pump to move water from the fish tank to a filter tank. The filter tank is filled with media that houses nitrification bacteria. This describes nothing more than a standard aquarium, and such a setup can be very stable, needing little in the way of maintenance if the ratio of fish to bacteria stays stable, and if distilled water is added to the system to compensate for evaporation losses.
The addition of plants to such a system runs into an immediate problem. Some plants cannot survive with having their roots constantly submerged in water. They need to be able to have access to air. One way of doing this is to periodically drain the upper media tank several times a day. A good mechanical way of doing this is to use a self-starting siphon called a “Bell Siphon“.
In short, a Bell Siphon will start to siphon water from the upper tank when the water reaches a certain depth. It will stop pulling water out of the upper tank when the water level drops below the rim of the Bell dome, which is typically near the bottom of the container. If the container is sloped toward the siphon, then most of the container will be completely drained.
This simple siphon works fine for a small aquaponics system. Something like the one shown to the right. This is a 150 gallon tank with an 80 gallon media bed. At the time of this photo, I was experimenting with Bell siphons, and had not added media to this project.
But what happens when you have multiple fish tanks? What happens when you have multiple media beds for your plants? What do you do when you want to add other aquatic animals besides just fish? Like freshwater prawns or mussels?
As I continued to play with aquaponics systems, the next thing I knew I had over a thousand gallons of fish tanks, and I was trying to find ways to circulate their water, and also to be able to drain them when I needed to clean them. This is what I came up with.
This system doesn’t even count the plant grow beds. It also uses a common sump tank as a shortcut. It did have the advantage of allowing me to drain a tank if I needed to do so, but with the disadvantage of requiring me to re-route the circulation if I wanted to cut off a center tank.
I actually built this system, and documented it on my permaculture website, with a video of it in action. You can see this here.
And I ran into a problem. Okay, one of the problems I had is that I had to move, and was required to disassemble the system.
But what I consider to be the bigger problem is how the system worked together. If I added grow beds to the system, I had to be concerned with my sump “bottoming out”.
The grow beds that I want to use are two feet wide, four feet long, and 14 inches deep, with 12 inches of media. This translates into 60 gallons of media and water together, or about 25 gallons of water per grow bed. This means I can have no more than 7 grow beds before my sump goes bone dry. Or less than 6 grow beds if I want to keep my sump pump underwater.
This also doesn’t account for water diverted to strawberry towers, lost in evaporation, or used in other ways. I would like the ability to use 10 grow beds or more, and use the sump itself (with a screen around the pump) for growing catfish. So a certain amount of water must remain in it.
This is what I came up with… multiple tanks, multiple grow beds. Of course, the sump would have to be larger, just in case all the Bell siphons achieved synchronicity and allowed all the grow beds to fill up at once. There would have to be enough water for everything.
Each of those red handles represents a valve that can be turned off or on by hand, and that I would be expected to fiddle with to get the right rate of flow for the system. And while this is quite acceptable with a smaller system, it becomes a problem larger systems.
Luckily valves and pumps can be controlled through electronics. I wanted an inexpensive method that I could create, and that I could offer to the Maker and Aquaponics community. I’ll talk about that next as I more formally describe the scope of this project.
It’s been a week since I attended the UBM West conference in Anaheim, and I’ve acquired a new fascination with the Internet of Things. In fact, I’ve been more than a little fixated on it since coming home.
I have been having discussions with various friends in engineering about the IoT, and I can see that there is a lot of potential here, but also there is a lot of confusion, and companies working at cross purposes. The consumer marketplace is quickly adopting many different IoT ideas, while manufacturing seems to be talking a great game, but is adopting the Industrial Internet of Things (IIoT) slowly – if at all.
One of my software friends is pushing the Internet of Data – the idea that the device doesn’t matter, only the data. As part of the setup, the device explains to the network what it is, what it can do, and what data it can provide. It is up to the network to determine how to use this information.
Unfortunately, there is not industry standard for data sharing in the IoT. There is no real standardized Human/Machine Interface (HMI) to allow a human to interact with a local network of IoT to do useful things. The IFTTT web service is a useful idea of how such an HMI might work, but I’m having a hard time visualizing how it would work in a local network setting – where I could control the devices in my home through my tablet computer, or where a manufacturer could use it to choreograph several manufacturing robots to work together.
I’ve learned that there is a lot of pre-existing infrastructure and technologies for IoT, and there are several services that hook into it. The problem is getting them all to work smoothly together.
But reading about it all is completely different from actually doing it. And to learn, it is often best to create a project to accomplish something, and then learn from that.
So I’m starting a project.
If you know anything about me, you may know that I’m interested in permaculture. Permaculture is the creation of sustainable agricultural systems by studying and simulating the ecological systems found in nature. It is the idea of working with nature, fitting our society together with ecology. There are principles of design that guide permaculture, and they are useful – but they all boil down to a simple idea, human observation and reaction as a form of feedback is key to an agricultural system.
I’ve been writing about urban farming and aquaponics in my blog, “Fresno Backyard Harvest” for a few years now. Aquaponics has been of great interest to me as part of urban farming and permaculture. And I would like to better automate my urban farm, with controls that monitor plant moisture, measure water quality for my fish, and adjust water levels when necessary. I’d also like alarms when something goes wrong, and I would like to see how much of my urban farm I can measure.
For my first project, I intend to create something that will control a small aquaponics setup. I will use it to monitor various sensors, and report back to me. It should also control water flow.
Right now, I’m in the planning stage. I’ll keep a running journal of how I decide what to use, and what my designs look like. I’ll also keep a Github repository of each project.
You’ll be able to find my progress in the “Projects” category of my blog. Starting with this one. As my projects split off, they’ll be given their own categories.