A test for predicting propensity of activated sludge to acute filamentous bulking

Filamentous bulking is a solid-liquid separation problem well known to activated-sludge plant operators. The use of curative additives is a rather delicate solution and the tools developed to anticipate it seem limited. To complement existing sludge sedimentation monitoring tools, a new test to assess the propensity of activated sludge for filamentous bulking was developed. It consists of challenging the sludges by feeding them under conditions favoring filamentous bacteria for 24 hours. The effects of such an acute treatment on sludge settleability is subsequently assessed through a simple sludge volume (SV30) measurement with reference to a control. The sludge can then be evaluated as prone to bulking (unstable sludge) or not (stable sludge). Such a test can be used to predict the occurrence of filamentous bulking in activated-sludge treatment plants. This so-called acute bulking test requires simple equipment and can be done by any wastewater treatment plant operator.