For reference, here are a couple of plots from some tests I did last year on DO (no plants) under different operating conditions:
For these, there were four modes of operation:
- pump speed set to low with the venturi off.
- pump speed set to high with the venturi off.
- pump speed set to high with the venturi injecting air.
- pump speed set to low with the venturi injecting air.
The initial “high” DO is from the municipal source supply, which, as can be seen, eventually out-gases. Just having the solution moving and fluming does not necessarily saturate the DO by itself. Oh, take the plots with a grain of salt since getting accurate/repeatable readings of DO takes a bit of detail. During some of this collection I was still getting acquainted with what to do/not do. Just thought you might be interested in seeing those.
The data collection and testing that I was working on (with help from @anon32470837) was put on pause “temporarily” as I had more pressing items to work on. But, now that I see you’re looking at venturi injection, my interest has been peaked again. I’ll probably look to get back to experimenting with this in the near future and to compare notes.
Side note, I was also doing some experimentation with the addition of surfactants to the solution along with the aeration. That has some potentially interesting results, as well.