The present invention relates to an apparatus and method for the solidification of sludges by kneading sludges in soft ground layers with a hardener and solidifying the sludges.
As the conventional method for solidifying sludges deposited and accumulated in bottom portions of harbors, bays, rivers and lakes, there can be mentioned a method in which a hardener is added to sludge in situ and the hardener-incorporated sludge is kneaded. The reason why the sludge is solidified in situ in the deposited and accumulated state is that the amount of the water contained in the sludge is held to a minimum and the solidification treatment can be performed conveniently. If the sludge is dug out and placed on the land for solidification, the water content in the sludge is increased greatly compared with the sludge deposited naturally.
This known method, however, is defective in that when the deposited sludge is kneaded and agitated by a kneading machine or the sludge is dredged, sea water or the like is contaminated in a broad region to cause secondary pollutions such as the generation of bad odors. Moreover, when the sludge is agitated, water or untreated sludge flows from neighboring sludge layers into the sludge being treated, and therefore, a large quantity of a hardener must be added. In this case, the hardener supplied in such a large amount readily flows into neighboring sludge layers and is wasted. Agitation of the sludge or the like is performed by agitating blades of the kneading machine. Accordingly, the sludge being treated is not completely separated from the sludge present on or around the outer periphery of the rotation locus of the agitating blades and therefore, uniform kneading of the sludge and hardener is not attained, and it is difficult to perform the solidification treatment in good kneading conditions.