Rheological characterization of centrifuged thickened waste excess activated sludge (EAS): the maceration effect on sludge pumpability

The purpose of this study is to determine how the rheological characterization of centrifuged thickened waste excess activated sludge (EAS). Wastewater treatment plants (WWTP) contain a number of transport operations of suspensions with special flow characteristics. Flow characteristics, in particular viscosity related effects, vary from very water-like to strongly non-Newtonian. This study uses a flow loop (or on-line apparatus) for pumping the EAS. The pressure loss versus flow rate measurement along a circular straight pipe (tube viscometer) provides the rheological data. As a complement, a rotational rheometer, Physica by Anton-Paar, was used to perform constant shear rate (CR) measurements on sludge samples. Depending on the flow rate, but within the laminar flow regime, the reduction in pressure loss is order of 30 − 40%. As expressed in the apparent viscosity this result in a ten times reduction, similar result reported in [4]. The obtained result indicate that a macerated EAS TS-content value may be chosen 1 − 2% higher than the reference sludge with remaining pumpability and laminar flow condition. Biogasmax is a project aiming to reduce the use of fossil fuels in Europe providing that biogas is a good technical, economical and environmental alternative as vehicle fuels. The specific aim for Stockholm Water is to increase the biogas production at the existing waste water treatment plant in Henriksdal, Stockholm. This report is a part of an evaluation study of a method for disintegration of waste activated sludge aiming at an increased biogas production potential.