How is the F/M ratio calculated?

The F/M ratio, which stands for food to microorganism ratio, is a key parameter in assessing the performance of biological treatment processes in wastewater operations. The F/M ratio is calculated by taking the influent biochemical oxygen demand (BOD) and dividing it by the mass of mixed liquor volatile suspended solids (MLVSS) in pounds (Ibs).

In this context, influent BOD represents the organic matter load entering the treatment system, while MLVSS is an indicator of the biomass available to treat that organic matter. The ratio itself provides valuable insights into the biological treatment process; a higher ratio may indicate an excessive organic load relative to available microorganisms, while a lower ratio might suggest an underloaded system with insufficient food for the biomass.

It's important to note that while options referencing COD and mg/L might be relevant in other contexts, they do not accurately represent the standard formula used to calculate the F/M ratio. Specifically, the calculation must use the correct units and measurements: influent BOD in pounds, divided by the mass of MLVSS, which is also measured in pounds.