A Class C operator monitors and recognizes. A Class B operator calculates, adjusts, and chooses among process strategies deliberately. This guide takes the F:M ratio and settleability concepts you already know and turns them into full calculations you can use to actively drive process decisions — how much to waste, how to set RAS, which process configuration your plant is running and why, and how the activated sludge process begins to remove ammonia through nitrification.
The F:M Ratio: Full Calculation
The Food-to-Microorganism (F:M) ratio compares the organic load entering the aeration basin (the "food," measured as BOD) to the biomass available to consume it (the "microorganisms," measured as MLVSS):
F:M=V×X×8.34Q×S0×8.34=lb MLVSS in aeration basinlb BOD applied/day Where:
- Q = influent flow to the aeration