Issues with dry filters when running turbidostat

Software
1

Hi everyone, we are encountering a problem with our filters to and from the pump drying up. This is happening specifically when running a turbidostat which might have a longer waiting time before dosing due to slow growth.

My idea was adding a regular dosing to the preset turbidostat mode that includes periodic addition and removal of a small amount of media just to keep the filter wet. Furthermore, I presume that there might arise issues if this “wetting” is either running or tries to run when the media is being exchanged when target OD has been reached and detected.

I am not very familiar with the coding used for the Pioreactors so i have had troubles trying to formulate the code necessary to perform this task. I assume using the RepeatedTimer class is a good option for this task.

2

Hi @Ms2013DT,

Another option is to use an experiment profile to run simultaneously to your turbidostat. For example, consider the following profile:

experiment_profile_name: run media periodically

metadata:
  author: Cam DP
  description: Avoid drying the filter by running the media pump occasionally. 
  
common:
  jobs:
    add_media:
      actions:
        - type: repeat
          hours_elapsed: 0
          repeat_every_hours: 1.0
          actions:
            - type: start
              hours_elapsed: 0
              options:
                ml: .25
    remove_waste:
      actions:
        - type: repeat
          hours_elapsed: 0.01
          repeat_every_hours: 1.0
          actions:
            - type: start
              hours_elapsed: 0
              options:
                ml: .50

This profile adds 0.25ml of media every hour, and removes 0.5ml every hour (offset by a few seconds)¹. The profile and the turbidostat can run simultaneously, and if they happen to overlap², an error will be thrown on the one that comes seconds - that’s okay, it won’t crash it, but it’ll just try again in the next cycle (for a turbidostat, that’s ~30s I believe).

¹ Please change these to better values!
² Which I think is unlikely: by problem definition, your turbidostat runs infrequently, and dosing 0.25ml of media takes a fraction of second.

To use this solution, you can copy and paste the above into a profile in your Profiles webpage, and run it when you run your turbidostat.