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Enzymatic pretreatment effects on dewaterability of anaerobically digested municipal were examined. A low-cost multienzyme mixture was used, including protease, lipidase, α-amylase-Aspergillus oryzae, and anaerobic bacteria. After 16 hours of mesophilic incubation and polymer conditioning, dewatering by bench-scale press showed a 15 mg/L enzyme dose to increase cake solids by a factor of 2 to 3 depending on the polymer dose used. At a polymer dose of 24 lb/ton DS, the cake solids was over 40%. Thus, in the common polymer dosage range, enzyme use doubles the cake solids attainable with no enzyme. This represents the ability to halve the total mass of dewatered biosolids. Incubation time was also found to be an important parameter in optimizing enzyme efficacy. Field emission scanning electron microscopy clearly revealed the fibrous extracellular matrix of the biosolids to be destroyed after 16 h of enzyme treatment. Measurements of extracellular protein and polysaccharide also showed the multi-enzyme mixture to reduce both of these constituents significantly. The enzyme doses necessary for these effects appear to be very cost effective. The product cost is relatively low (about twice the cost of the polymer) because it is a cultured broth requiring no purification of specific constituents. Results indicate considerable promise for enhanced dewatering at full scale through enzymatic pretreatment.

Document Type: Research Article


Publication date: 2006-01-01

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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