What is the typical range for MCRT in most activated sludge processes?

In most activated sludge processes, the typical range for Mixed Cell Residence Time (MCRT) is usually found to be between 5 to 15 days. This time period is significant because it allows microorganisms in the system to stabilize and effectively break down organic waste. Maintaining the MCRT within this range is crucial for achieving optimal treatment performance since it balances the growth rate of microorganisms with the hydraulic retention time of the wastewater. A proper MCRT supports the development of a healthy biomass, which is essential for efficient biological treatment.

If the MCRT is too low, it can lead to insufficient biomass in the system, compromising the treatment process. Conversely, if the MCRT is too high, it could result in the loss of treatment efficiency due to factors like the accumulation of inactive or older biomass. This balance is key to ensuring that the activated sludge process operates effectively, making the selected range a standard for the industry.