Microscopic Exam - Here you want to note floc size & density, bacteria in free solution, protozoa, metazoa (rotifers), filamentous bacteria, non-filamentous bulking (India Ink test). Changes in floc and protozoa are the first indicators of changes - daily observation helps you know what is normal and spot potential problems early on.
SV30 & SVI - Settling tests give great information on floc quality entering the secondary clarifier. Look beyond just the 30 minute number - note settling rates, supernatant turbidity, let it settle for an additional time to more simulate your clarifier (2 - 4 hours), floating solids after longer settling, and a shaggy appearance caused by filamentous organisms. It is important to use the same vessel for the SV30 test each time - wall effects in cylinders and settleometers can change results.
Oxygen Uptake Rates - aerobic biological waste treatment microbes use oxygen to treat influent pollution. The OUR or DOUR test saturates a sample of MLSS with oxygen and you read oxygen consumption over a short time period. Report results in mg O2/L/hr. If you divide the OUR result by MLSS or MLVSS in grams - you have the standardized oxygen uptake rate - just make sure that you use MLSS or MLVSS as the divisor each time. As with all tests, be consistent.