Mean Cell Residence Time. An expression of the average time (days) that a microorganism will spend in the activated sludge process.
NOTE: Operators at different plants calculate the Total Suspended Solids (TSS) in the Activated Sludge Process, lbs (kg), by three different methods:
- TSS in the Aeration Basin or Reactor Zone, lbs (kg)
- TSS in the Aeration Basin and Secondary Clarifier, lbs (kg)
- TSS in the Aeration Basin and Secondary Clarifier Sludge Blanket, lbs (kg)
These three different methods make it difficult to compare MCRTs in days among different plants unless everyone uses the same method.