How can the Mean Cell Residence Time (MCRT) be increased?

Increasing the Mean Cell Residence Time (MCRT) can be achieved by increasing the Mixed Liquor Suspended Solids (MLSS) concentration in a biological treatment process. MCRT is a measure of the average time that microorganisms remain in the treatment system.

When MLSS is increased, it indicates a greater concentration of active biomass in the reactor, which allows for enhanced biological treatment processes. Higher MLSS concentrations imply that more microorganisms are present to break down organic material, which can lead to increased resistance to variations in loading and better overall treatment efficiency. Consequently, the time that the biomass remains in the treatment process (and hence its MCRT) can be effectively prolonged.

This connection is crucial in wastewater treatment, as it helps optimize the performance of biological reactors, specifically in systems like activated sludge processes where the balance between biomass production and decay is sensitive to the operational parameters. By increasing the MLSS, the retention of cells in the system is promoted, directly enhancing the MCRT.