To know if cleaning was good you must control it.
I chose to do this by examining the waste water. I take a sample of the last rinsing water. From this water I filtrate three times 100ml over a membrane. Then I add the appropriate medium. After that the plates are incubated at the right temperature during a specific period. When time is up, plates are inspected. One can see this in the figure below.
This technique takes several days before result. To become a quick indication of the cleaning I also take ATP swabs in the tank. In the next figure you see how this is done
Two weeks ago I started to examine whether there are still organic compounds in the last rinsing water. Do you think this is useful? Or maybe not in all cases? Should I do some other extra tests?