Two olive mill wastewaters (OMW) samples, OMWa and OMWb, containing different polyphenolic loads were used for decontaminating an unauthorized dump site in the Campania region, south Italy. In a bench-scale experiment, OMWa at pH 6.0 (OMWapH6.0) and 4.7 (OMWapH4.7), OMWb at pH 4.7 (OMWbpH4.7) and OMWa free of the polyphenolic moiety polyphenol-free OMWa (PF-OMWa) were added to the soil for a 96 h contact time. At 96 h, OMWapH4.7 was more effective than OMWapH6.0, with Cd, Cu, Pb and Zn removal percentages of 30.7-68.1. Cd and Pb levels were 6.0 and 915 mg kg(-1), respectively, decreasing below the regulatory limits for industrial and commercial areas (15.0 and 1 × 10(3) mg kg(-1), respectively). A threefold decrease in Zn levels was also observed from 13.5 × 10(3) to 4.3 × 10(3) mg kg(-1). The metal removal efficiency of PF-OMWa dropped from 30.7 % to 15.6 % for Cd and from 37.9 % to 1.3 % for Pb. OMWbpH4.7 at 96 h was more efficient than OMWapH4.7, with mean removal percentages of 32.5 versus 7.8, respectively.