PURPOSE: To produce easily a flocculating agent having highly effective power by solutionizing cement with a chemical.

CONSTITUTION: A chemical that acts like a flocculating agent and a chemical that acts like a coagulating agent coexist in a cement component and therefore if the cement is solutionized by a chemical, the cement is usable as a flocculating and coagulating agent as well as a flocculating and coagulating assistant. When, for example, calcium incorporated most in cement is considered, calcium is made into calcium sulfate if the chemical to be used is sulfuric acid, and it is made into calcium chloride when it is dissolved with hydrochloric acid. The flocculating agent for different purposes is easily obtd. simply by changing the chemical to be used in the stage of dissolution in the above-mentioned way. Moreover, cement is available anywhere at a low cost and if water is used as a medium in use, an extremely large chemical change is obtd. and the required effect of treatment for preventing pollution is quickly obtd.