Recovering coagulant from treating residual waters by dissolving hydroxide formed, residual and unused acid, adding and formaldehyde, washing aminoplast and reusing water

The hydroxides formed during coagulation in residual acidic waters, residual acids or unused acids are dissolved. Urea and HCHO are added to the resulting soln. heated to 40 deg.C. The aminoplast formed is washed. The washing waters obtd., together with those resulting from the condensation reaction of the
resin, are used in the coagulation of the residual waters.