Papermaking sludge and spent pickling liquor were recycled to synthetize an organic polymer flocculant (LA) and polyferric chloride (PFC), respectively. They were used in synthetic dyeing wastewater treatment - disperse yellow (DY) and reactive blue (RB). Effect of PFC, dual-coagulant (PFC + LA) and second dose of LA after breakage period (PFC - LA) on color removal, floc regrowth and floc structure were comparatively investigated. The result showed that PFC could achieve excellent color removal, around 90% for the two dyes at optimal dosages. LA addition after PFC gave a little higher color removal efficiency but much larger flocs. Specifically, ratio values of PFC-flocs for DY and RB were approximately 1.43 and 0.59 respectively, compared with 1.75 and 0.72 for flocs formed by PFC + LA. Floc recoverability was also much higher at the usage of LA when there was a breakage period, and they were in the order of PFC - LA > PFC + LA > PFC. Additionally, comparing with those of PFC, roughly opener flocs were reformed by PFC - LA and PFC + LA after breakage because of LA bridging. For instance, TWV values (%) were 10.24, 13.24 and 16.16 respectively for PFC, PFC + LA and PFC - LA in RB treatment. LA favored charge neutralization, adsorption and bridging in the coagulation process. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.