Algae bioreactor system design [HELP]

[haylequin]

I'm trying to grow algae in a laboratory bioreactor. Our current setup has a pump pushing water from a large gravity-drained tank, through tubes containing algae, and back into the top of the tank.

We are having an issue with removing oxygen bubbles from the water as it re-enters the tank. We installed a T-shaped PVC joint and hoped that the bubbles would leave through an open tube at the top of the T, but instead atmospheric air is being sucked into the tank via this tube (see links below).

Any help or suggestions for fixing this would be truly appreciated

What we want our system to do: [URL unfurl="true"]https://imgur.com/eIpSsMh[/url]

What our system is actually doing: [URL unfurl="true"]https://imgur.com/RoZcbDH[/url]

 

[MikeHalloran]

The T is a crappy eductor, but it works well enough to interfere with what you are trying to do.

PVC is cheap. Try something else.



Mike Halloran
Pembroke Pines, FL, USA

 

[IRstuff]

Seems to me you need to figure out where the oxygen is coming from in the first place and eliminate at the source. You show oxygen coming out of the tank with the algae at the start. How did it get there? Is it the natural oxygen from the algae? Perhaps you need to consider having another pump

TTFN (ta ta for now)
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[EngineerTex]

If you want to keep it cheap:

1) After the oxygen-letter-outer tee, in the downward-flowing section, increase the pipe diameter to as large as you can get your hands on and make that section as long as possible. The object is to keep the fluid speed as slow as possible so that any bubbles in the system will rise against the flow, as opposed to remaining trapped.
2) Consider installing a pneumatic check valve on the outlet of the top end of the tee. Make sure that it is pointed in the correct direction to prevent pressurizing your system. ALSO - make sure that your system can withstand a vacuum, which it may eventually develop at some point.
3) Make sure that there is enough fluid in the system so that the flow of the water into the tee isn't splashing about, introducing bubbles that way. How much higher? Enough so that you don't see any movement on the top surface of the water above the tee except for the gas release.

Engineering is not the science behind building. It is the science behind not building.

 

[EngineerTex]

Notably, I did not coin the expression regarding the infamous fluid-letter-outer:

https://youtu.be/6Rt89-QCFgs?t=324

Engineering is not the science behind building. It is the science behind not building.

 

[hydtools]

Why not just return horizontally, below tank water level. Get rid of the oxygen-letter-outer. Get rid of air entrainment, air-letter-inner.

Ted