Akademik Veri Yönetim Sistemi
JOURNAL OF RESIDUALS SCIENCE & TECHNOLOGY, cilt.2, sa.4, ss.233-240, 2005 (SCI-Expanded)
Historically, sludge was one of the first materials for which non-Newtonian behavior was recognized and quantified, due to the engineering challenge of properly pumping this material. Rheology is now employed in many fields, and over recent decades, more sophisticated rheometric techniques have been developed for a range of applications. This paper reviews some of these newer techniques and demonstrates their use in the characterization of sludge. The conventional technique of controlled shear rate (CSR) is used on a waste activated sludge with and without chemical conditioning. The "stress overshoot" phenomenon is observed and discussed, as it complicates the conventional interpretation of such test results. Newer methods are also applied for comparison: a creep test, which uses a constant applied stress while deformation is measured over time, and a strain amplitude sweep test. Neither of these methods experienced the type of difficulties seen with the CSR test. The creep test provides the critical stress level and, with sufficient data, the four parameters defining the Burgers model of deformation. The strain amplitude test provides the yield stress without model assumptions or reliance on data beyond the yield point.