Methods of modification of zero-valent iron (ZVI) to improve its performance in removing contaminants from a discharge stream. In some aspects, the methods include contacting ZVI-impregnated disks with solutions containing metal cations such as Ni2+, Cu2+, Fe2+, or Pd2+. In some aspects, a wastewater stream is treated with a metal cation solution, then passed over ZVI. Compositions for treating wastewater include ZVI that is modified with a metal cation solution.