The present invention relates to a method for removing a heavy metal from and/or dissolving calcium and/or magnesium scales in water or an aqueous system comprising using .gamma.-polyglutamic acid (.gamma.-PGA, H form), and/or one or more of its salts (i.e., .gamma.-polyglutamate in Na.sup.+ form, .gamma.-polyglutamate in K.sup.+ form, and .gamma.-polyglutamate in NH.sub.4.sup.+ form) and/or .gamma.-polyglutamate hydrogel as chelating agents for removing heavy metals and/or dissolving agents for removing calcium and/or magnesium scales from water or the aqueous system.