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Abstract

An improved process of treating sludge to provide a stable product for use as a beneficial soil or fertilizer for agricultural lands which includes the steps of: (a) mixing sludge with at least one alkaline material in an amount sufficient to raise pH of the mixture to a level of at least 12 and to increase percent solids in the mixture to at least 40% by weight, and such that odorant sludge organics and inorganics are bound to adsorbent particles of the alkaline material, (b) aerating and drying the mixture by agitation and heating to stabilize the mixture and increase the percent solids to at least 50% by weight, and (c) pasteurizing the dried mixture at a temperature at or above 52.degree. C. by application of heat resulting from an exothermic reaction of the alkaline material with water in the sludge, wherein the step (b) is carried out in a mechanical means selected from the group consisting of a drum dryer, a pelletizer, and a fluidized bed apparatus, and wherein the heat applied for drying in the step (b) reduces the amount of additional heat required for pasteurization in the step (c) thereby reducing the amount of alkaline material needed for the exothermic reaction, the improvement wherein sufficient time is allowed under step (a) prior to step (b) to enable sufficient slaking of the alkaline material in the mixture to prevent removal of the mixture as dust during step (b). The process reduces the amount of or prevents dust formation in the aeration/drying step.

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First Claim