Field Applications Of Cyclodextrin-aided
Sludge Dewatering
Author(s)
S. Banerjee & S. Wright
Abstract
Cyclodextrins (CDs) increase the cake solids and the drainage rate of belt- or
screw-pressed biological or primary sludge when added to the sludge slurry
along with conventional sludge conditioning chemicals. These benefits are
obtained at very low CD dosage. For example, a 2.8 percentage point increase in
cake solids was obtained in a full-scale trial with mixed primary and biological
sludge at a paper mill wastewater system. CDs also decrease the specific
resistance to filtration and increase the capture rate of solids during belt pressing.
They are able to aggregate charged polymers, and, by inference, sludge particles
treated with the polymers. Results from full-scale trials at two paper mills and a
municipal wastewater treatment system are discussed. In all cases, some
combination of higher cake solids, better drainage, better filtrate clarity and
lower polymer dosage was obtained. The CD application for sludge dewatering
is being introduced commercially.
Keywords: sludge, dewatering, cyclodextrin, polymer, cake solids.
1 Introduction
Cyclodextrins (CDs) are torus-like rings assembled from six, seven, or eight
glucopyranose units: α-, β-, and γ-CD, respectively. The structure of β-CD is
illustrated in figure 1. CDs have a cylindrical structure with a hydrophobic
cavity and a hydrophilic exterior. They are non-toxic commodity chemicals, and
are prepared by the action of bacteria on starch [1]. Practical applications include
solubility enhancement of hydrophobic solutes such as pharmaceuticals [2], the
Keywords
sludge, dewatering, cyclodextrin, polymer, cake solids.
Related Book
Other papers in this volume
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