Papermaking Sludge

TABLE 3.20 Mechanical (tensile) properties of long cellulose fiber (modified from [141]) 

Paper sludge has traditionally been disposed of by landfilling, composting, incorporation into cement, and incineration. The latter option, in turn, creates another problem, namely, disposal of the resulting ash, which often makes up to 50% (and sometimes as much as 80% or higher) of the volume of the sludge itself. 

The principal components of ash are calcium carbonate— in the form of precipitated calcium carbonate (PCC) or ground calcium carbonate (GCC)—that typically constitutes 20% and up to 75% of dry sludge content, and clay. These two minerals are typically loaded into paper as a coating and filler to improve the mechanical characteristics as well as the appearance of paper. The resulting papermaking sludge, particularly mixed office paper sludge, consists primarily of two major components, that is, fiber and minerals finely mixed with each other. 

Biodac is supplied by Kadant Grantek (Green Bay, WI) for about 180/ton (9 cents a pound). Its major application is as an agricultural carrier for herbicides and pesticides, animal bedding, cat litter, oil absorbents, filler for GeoDeck composite deck boards, and components of GeoDeck composite railing systems. 

When heated, Biodac , as well as rice hulls (see above. Tables 3.17 and 3.18), releases gaseous products. It is interesting that despite the principal differences in their chemical composition, the amounts of VOC produced by both the materials under heating are very close to each other. Data are given in Tables 3.21 and 3.22. 

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These data can be fully assigned to the papermaking sludge, from which Biodac was made. 

In a new development the aerobic activated sludge plant was replaced by a compact aeration reactor, in order to reduce the odor of the anaerobic treated process water and to eliminate CaCOs, which might cause problems when the biologically treated water is led back into the papermaking process [8, 9]. 

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