Water treatment methods and water treatment coagulants

Object of the present invention is to provide a method of water treatment using a coagulant, wherein the coagulant is formed by the secondary treatment minimizes contamination by alkali solution a phenolic resin residue caused coagulation. The method of water treatment in a membrane separation process after being treated in water coagulant added. The coagulant, a melting point of the alkali solution is 130 ~ 220 ℃ phenol resin. The coagulant treatment is obtained by the following reaction: In the presence of an acid catalyst, phenol and aldehyde react, in an alkali solution was added the aldehyde novolac type phenol resin obtained, and then, a base for resol-type secondary reactions in the presence of a catalyst.