In the title process, which improves productivity and wastewater clarity, paper is prepd. from pulp slurries contg. 0.1-1.5% solids and 0.01-0.5% (based on solids) highly-branched, high-mol.-wt. copolymer of diallyldimethylammonium chloride (I) with 0.1-3.0 mol% crosslinking monomers. A slurry of 0.8% fibers (wastepaper) contg. 0.02% I copolymer with 0.1 mol% triallylmethylammonium chloride had dewatering time (250 mL filtrate) 5.1 s and gave a sheet contg. 97.5% solids, vs. 5.7 and 95.2, resp., with I homopolymer, and 6.5 and 93.1, resp., with no polymer. [on SciFinder (R)]