If the RAS rate is too high, what is the typical primary result?

When the Return Activated Sludge (RAS) rate is set too high, it results in an overload of solids in the clarifier. This can occur because the clarifier is designed to handle a specific volume of sludge, and exceeding this volume can lead to an inability to effectively separate solids from the treated water. As a result, the excess solids can overflow, leading to a 'washout' situation where solids do not remain in the clarifier for adequate settling and instead are carried out with the treated effluent. This situation can compromise the treatment process, potentially resulting in non-compliance with discharge regulations. Hence, the primary consequence of a high RAS rate is that solids will overload the clarifier and wash out, undermining the efficiency of the wastewater treatment process.