the sludge and lime at atmospheric conditions leads to hydration reaction although lime defined here as substantially pure calcium oxide is utilized in this embodiment other substances consisting of or containing calcium oxide or calcium carbonate or calcium hydroxide may be used such as quicklime dolomitic lime or lime kiln dust cement kiln dust therefore although lime is used herein the additive is selected from the group comprising or consisting of calcium oxide calcium carbonate and calcium hydroxide the selection may be dependent on availability and ph level desired because some members of the group may not be effective enough to raise the ph to the desired predetermined level for example if the desired predetermined ph level is twelve dolomitic lime may not be volatile enough to raise the mixture to that level the dewatered sludge may contain anywhere from 10 60 of dry solids although 15 50 is more usual the lime sludge ratio by weight can vary from 25 to 200 so that for every pound of dry solids of sludge from 0 25 to 2 0 pounds of lime may be added as this equation shows the hydration of the lime requires water the free and perhaps some or all of the bound water in the dewatered sludge is utilized in the reaction the resultant hydroxide which in this embodiment is ca oh 2 is the.