PURPOSE: To form condensation bodies for a short time, by adding high concn. sodium silicate solution and high concn. acidic solution.

CONSTITUTION: Extremely hard gelled bodies are obtained under a hydrous condition by injecting high concn. sodium silicate solution and high concn. acidic solution to muddy water and by curing after rapid agitation. If slow agitation, gelling becomes imperfect, and created gelled bodies flow out from the meshes of a filter cloth when the bodies are pressurization dehydrated. The Na+ ions of sodium silicate react with heavy metals in muddy water and stay in muddy water, and the surfaces of solids in muddy water are mixed with acidic solution after the surface are covered with sodium silicate solution, thus allowing the prevention of the re- rendering of heavy metals