Food-to -micro-organism ratio, d-1 is denoted as X/M

X/M= QSo/VX where, Q is Flow to the reactor m3/d and So is Substrate concentration in the influent i.e BOD or COD V is the volume of reactor and X is the concentration of the MLVSS

The F: M ratio describes the degree of starvation of microorganisms. Because biological treatment processes should remove nearly all influent substrate the F; M ratio also expresses the potential food availability to the microbial population.

The SVI can be used to estimate the concentration of VSS ad TSS in the recycle line if the ratio of VSS to TSS in the mixed liquor is known. Typically the ratio is 0.75 to 0.80 A low SVI is indicative of a sludge that settles well.

Yes, definitely. After checking many samples, for a particular sample, when these parameters are estimated, the relationship becomes apparent. Microorganisms depend on food for metabolism. Their metabolism in sewage, decides the BOD. COD too depends on the amount of organic matter in the sludge or sewage, which depends on the metabolism and sludge is a result of metabolism, degradation, decomposition; thus all parameters are inter-linked.

Depending the F/M ratio your system will be either food limited or Oxygen limited. Hence at certain F/M ratio you have a low SVI - this is typical when neither food nor O2 is limiting growth. Which exact value that will give a low SVI also depend on your system configuration and the water temperature. More information can be soght ie. by

Process Control of Activated Sludge Plants by Microscopic Investigation Dick H. Eikelboom IWA Publishing.

Food-to -micro-organism ratio, d-1 is denoted as X/M

X/M= QSo/VX where, Q is Flow to the reactor m3/d and So is Substrate concentration in the influent i.e BOD or COD V is the volume of reactor and X is the concentration of the MLVSS

The F: M ratio describes the degree of starvation of microorganisms. Because biological treatment processes should remove nearly all influent substrate the F; M ratio also expresses the potential food availability to the microbial population.

The SVI can be used to estimate the concentration of VSS ad TSS in the recycle line if the ratio of VSS to TSS in the mixed liquor is known. Typically the ratio is 0.75 to 0.80 A low SVI is indicative of a sludge that settles well.

F/M ratio has a effect on sludge age and sludge age has influence on SVI