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.
