What should be done to maintain the microorganisms population during a hydraulic overload?

To maintain the microorganisms population during a hydraulic overload, decreasing the Waste Activated Sludge (WAS) is an effective approach. In situations of hydraulic overload, it is crucial to ensure that the microorganisms, which are key to the biological treatment process, are preserved and provided with sufficient time and environment to acclimate to the increased flow rates.

By reducing WAS, you are keeping more of the active microorganisms in the system instead of removing them. This helps to support the treatment process and allows for the microbial community to have a better chance of handling the increased organic loads. Retaining more microorganisms in the system can mitigate the negative effects associated with hydraulic overload, such as dilution and washout of the biomass.

Other actions, such as decreasing Dissolved Oxygen (DO), could negatively impact the microorganisms' health, while increasing Return Activated Sludge (RAS) or Waste Activated Sludge (WAS) might further complicate the microbial population balance during an overload situation. It is essential to strike a balance to ensure that the microorganisms can thrive and effectively treat the inflow.