Increasing cake solids of cellulosic sludge through enzyme-assisted dewatering

Brief treatment of wood pulp fibers or cellulosic sludge with cellulase enzymes ruptures the fibers at the kinked regions. Dewatering these fibers with a belt press simulator leads to higher cake solids because of better cake consolidation with the shorter fibers. The void volume of the cake is reduced. A three to six percentage point increase in cake solids is obtained depending upon the enzyme dose applied, the nature of the sludge used, and the exposure period. Examples are provided with both hardwood and softwood fiber and with primary sludge from several paper mills. The economics are attractive and are likely to become increasingly more so as enzyme prices continue to drop and the cost of landfilling rises.