Here is an experimental set-up utilizing "slucket buckets" in a, more or less, DIY configuration.
Slucket buckets have sloped bottoms along with a bottom port allowing for improved drainage over conventional RDWC type set-ups. Water is injected from the bottom ports on each of the growth modules while water is removed from the bottom port at the reservoir. Return from each of the growth modules is via a 3 inch diameter pipe.
Several valves comprise the pump manifold allowing the direction of flow to be modified for filling the system, for run-time operation, and for pump assisted draining of the system.
There are a couple of goals, here. 1) attempt to eliminate air pumps/stones through the use of a needlewheel pump and venturi 2) online process monitoring 3) serve as an experimental platform for a variety of ambitions.
Control Bucket / Reservoir:
Inline PH / Temperature / ORP probes:
Conductivity / Temperature probes:
The various online probes are fed to milliamp transmitters which are then converted to streaming ethernet data. A remote embedded system provides monitoring/control. Included but not shown in the above are environmental CO2, humidity, and temperature sensors along with actuators for lighting control and CO2 injection. Lot's of work in progress here and may eventually integrate some "fancy" experimental sensor elements if the initial trial is successful.
Flooming / Aeration effect:
Air is injected before the needlewheel pump at a controlled rate to ensure sufficient pump suction at the reservoir. The air injection mechanism is nothing more than a polypropylene tube jammed into the water outlet pipe (bottom port) in the reservoir. The water velocity is sufficient that a venturi effect is produced creating vacuum on the air inlet.
Eventually this set-up will be moved into a growth space for real-world data collection.
There are already several non-optimal things I've noted with this configuration but I'm thinking they're relatively minor at this point. Can always go back and hack in fixes, eventually.
1) Started with a commercial venturi for air injection but it proved to be way too restrictive on flow. The needlewheel pump would cavitate and I had to remove it. Instead I just jammed a small tube into the pump inlet for now.
2) Configuration was arranged with the hopes that there would be sufficient pressure balancing between the four growth modules. Bypass piping was placed between the units in order to achieve this but, as it turns out, was not sufficient. The first two units receive greater flow. Simply modifying the length of tubing supplying the first two units (or otherwise) should resolve this (using flexible SPA tubing).
3) Air injection appears to be working ok but I would like to see finer micro-bubbles appearing at the growth modules. There could be several reasons for this including overall velocity of flow over distance, the venturi problem as noted, needlewheel pump improvement or, perhaps, not achievable. Needs experimentation.
4) Set-up is designed such that the system can be pumped dry during draining. However, I'm lazy and didn't spend a lot of time ensuring that the sump was below the inlet tubing. As such, most of the water is sumped but there is a small amount that remains in the piping. Lesson learned, don't be so lazy