A method of removing one or more heavy metals from municipal wastewater by use of a membrane separation process is disclosed. Specifically, the following steps are taken to remove heavy metals from municipal wastewater: (a) collecting a municipal wastewater containing heavy metals in a receptacle suitable to hold said municipal wastewater; (b) adjusting the pH of said system to achieve hydroxide precipitation of said heavy metal in said municipal wastewater; (c) adding an effective amount of a water soluble ethylene dichloride-ammonia polymer having a molecular weight of from about 500 to about 10,000 daltons that contain from about 5 to about 50 mole percent of dithiocarbamate salt groups to react with said heavy metals in said municipal wastewater system; (d) optionally clarifying the treated wastewater from step c; (e) passing said treated municipal wastewater through a submerged membrane, wherein said submerged membrane is an ultrafiltration membrane or a microfiltration membrane; and (f) optionally back-flushing said membrane to remove solids from the membrane surface.