After many year of process follow-up and troubleshooting in collaboration with wastewater treatment plant operators, MCR Process & Technology has developed new tools to assist operators in there daily tasks. The STIRO-SETTLOMETER is one of these tools, and was designed to meet a need for a more representative test, or measure, for evaluating sludge settleability in secondary clarifiers.

The STIRO-SETTLOMETER is a laboratory equipment inspired by the method and specifications given in the Standard Methods 2710C for the evaluation of the sludge settleability. From the laboratory results it is then possible to calculate the SVI (sludge volume index), SSVI (stirred sludge volume index) and ZSV (zone settling velocity) indexes.

It consists of a motor, mounted on a 2 liters cylinder, which actuates a low speed stirring mechanism. This mechanism limits the interferences associated with floc bridging and wall effects.

Comparing results obtained using the STIRO-SETTLOMETER with the classical SVI test (without stirring) can reveal the importance of filamentous bridging on sludge settleability, a bad floc formation or the presence of a non-filamentous bulking effect. The result of this test can help the operator define the process strategy to eliminate a bulking situation.