Acid mine drainage (AMD) generated by some coal mines in New Zealand is currently neutralized by the addition of alkaline reagents, triggering the precipitation of dissolved metals as insoluble hydroxides. This study investigated the addition of lignite-derived humic substances (HSs) before, during, and after neutralization of AMD based on two Stockton Mine treatment scenarios: the Blackwater Treatment Plant (BTP) and the Mangatini Stream-Sump (MSS). Supernatant samples collected during the sedimentation period were analyzed for basic water quality parameters: turbidity and suspended solids (SSs). The BTP scenario used calcium hydroxide [Ca(OH)2] neutralization, resulting in low supernatant turbidity (