High-Level Reduction of Organic Sludge by Multistage Ultrahigh-Pressure Dewatering Combined with Reversible Flocculation

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Multistage ultrahigh-pressure expression combined with reversible flocculation accomplished high-level reduction in volume of organic sludge. The water content of the compressed cake produced from excess activated sludge was finally reduced to 23 wt% by ultrahigh-pressure expression conducted at 50 MPa combined with reversible flocculation using inorganic electrolyte with multivalent cation. This new method reduced the sludge volume by 99.87 %. The relation between the average porosity of the compressed cake and the applied expression pressure suggests that the water content of activated sludge may be further reduced by greater expression pressure. It was shown that the complicated kinetics of expression of activated sludge under the ultrahigh-pressure condition was accurately described using the newly developed multistage creep model and that the model will be beneficial in evaluating the dewatering performance under various operating conditions.