Cj. Rivard et Nj. Nagle, PRETREATMENT TECHNOLOGY FOR THE BENEFICIAL BIOLOGICAL REUSE OF MUNICIPAL SEWAGE SLUDGES, Applied biochemistry and biotechnology, 57-8, 1996, pp. 983-991
Modern municipal sewage waste treatment plants use conventional mechan
ical and biological processes to reclaim waste waters. This process ha
s the overall effect of converting a water pollution problem into a so
lid waste disposal problem (sludges). The costs for conventional dispo
sal of Sewage sludges have risen dramatically because of increased env
ironmental mandates, which restrict their disposal, as well as a dwind
ling number of landfills. Previously, we determined that secondary bio
processing (specifically anaerobic digestion) was not effective in red
ucing the organic content and bulk of the sludge waste (1). Therefore,
we have examined the potential of a variety of pretreatment technolog
ies designed to disrupt the macrostructure of the sludge and thereby e
nhance its subsequent biodegradation. Two thermal/mechanical pretreatm
ents tested were found to have a dramatic effect on the subsequent bio
conversion of the microbial sludges. Both technologies evaluated, soni
cation and shear, were found to be affected by sludge solids levels, d
uration of treatment, and treatment temperature. Optimum sonication pr
etreatment occurred with sludge solids of 1% and treatment times of 4-
8 min. The most effectivee treatment temperature tested was 55 degrees
C. The optimum enhancement in bioconversion potential for the sonicat
ion pretreatment was 80-83% of the materials carbon oxygen demand (COD
) content. The optimum shear pretreatment occurred with sludge solids
of 1-2% and treatment times of 6-10 min. The most effective treatment
temperature tested was 87 degrees C. The optimum enhancement in biocon
version potential for the shear pretreatment was 88-90% of the materia
l's COD content. These data were the basis for US parent no. 5,380,445
, granted January 10, 1995.