Contaminated drinking water and other liquids are decontaminated by contact with sorbents to remove toxic contaminants such as arsenic, as well as non-toxic contaminants. In regenerating the spent sorbents, the waste stream contains both toxic and non-toxic contaminants but only toxic components must be treated as hazardous waste and subjected to strict regulations for disposal. The inventive method regenerates spent sorbents in a process that minimizes the amount of hazardous waste for disposal. The bulk of contaminants are non-toxic and are first selectively removed from the spent sorbent, generating a non-hazardous waste stream. Toxic contaminants are then removed from the sorbent, generating a hazardous waste stream. Because the bulk of contaminants was removed in the first waste stream, the lower concentration of toxic contaminants in the second waste stream requires less material (e.g., ion exchange resin) for hazardous waste decontamination and disposition.