A method for reducing sulfide in oilfield waste water includes contacting oilfield waste water with an oxidizer in the presence of an iron catalyst. The oilfield waste water includes sulfide that is oxidized to sulfate while avoiding formation of a colloidal or bulk sulfur precipitate. A method for recycling oilfield waste water includes contacting oilfield waste water with an oxidizer in the presence of an iron catalyst, the oilfield waste water comprising sulfide; oxidizing the sulfide to sulfate; avoiding formation of a colloidal sulfur precipitate, a bulk sulfur precipitate, or a combination comprising at least one of the foregoing; clarifying the oilfield waste water by contacting the oilfield waste water with a flocculant to form an aggregate precipitate; separating the aggregate precipitate from the oilfield waste water to form a recycled water; combining an additive with the recycled water; and disposing the recycled water in a downhole environment.