Anomalous pump behavior/configuration


we are troubleshooting the pioreactor in chemostat mode and believe that have identified some anomalous behavior:

  1. In chemostat mode, the vessel volume tends to decrease during an experiment suggesting that the dosing/pumping is off. The waste pump sometimes pumps twice relative to the media pump. Could this be related to waste_removal_multiplier=2 in config.ini?
  2. When cycle media, we notice that the media pump works intermittently whereas the waste pump works continuously (as judge visually by looking at the pumps).
  3. When we run both the media and waste pumps continuously, we observe that both now run continuously (without an intermittent pause in the media pump) but the waste pump seemingly runs at a higher speed (as judge visually by looking at the pumps).


Hi @samunozg,

This is expected behaviour, but probably poorly documented on our end.

  1. The waste pump runs an additional time (and it’s duration is controlled by waste_removal_multiplier) so that if there is a delta between waste pump and media pump (ex: more media than expected), the vial won’t overflow. Take a look at the docs section here. This also explains the importance of the waste tube height.

  2. Again, this is by design. We want to avoid overflows, so if the media pump moves more ml / second, it will eventually overflow the vial. By pausing the media pump momentarily, and continuously running the waste pump, we avoid an overflow.

  3. This could be caused by variability in the pumps: the waste pump you are using may be more efficient, or lubricated, etc.

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Thank you, @CamDavidsonPilon. I’ll try this shortly and report back.