The present invention relates to a method for direct treatment of liquid wastes containing up to 10% or 100,000 mg/L of arsenic by solidification/stabilization in a relatively cost effective and environmentally safe. The method also permits the simultaneous utilization other heavy metal bearing wastes (such as spent catalysts), in the solidification/stabilization of liquid wastes containing very high concentration of arsenic. It also deals with a method for converting liquid wastes containing very high concentration of arsenic into a non-leachable solid residue ready for final disposal. The direct treatment of liquid wastes containing very high concentration of arsenic by solidification/stabilization will eliminate the additional stage of converting liquid wastes to solid or semi-solid form prior to solidification/stabilization, thereby significant reduction in overall cost associated with arsenic waste treatment.