Sulfide removal in petroleum refinery wastewater by chemical precipitation.

Sulfide removal by chemical precipitation from petroleum refinery wastewater was investigated. The wastewater samples were taken from the flocculation pond influent of TUPRAS Kirikkale Middle Anatolia Petroleum Refinery Wastewater Treatment Plant (WWTP) and physicochemical treatments using conventional coagulants which were partial precipitant [FeCl(3) . 6H(2)O and FeSO(4) . 7H(2)O] and coagulant-aids [Ca(OH)(2) and CaCO(3)] were applied to both raw and sulfide added wastewater. Sulfide and chemical oxygen demand (COD) removal efficiencies of Fe(3+) ions alone for sulfide added wastewaters having different pH values varied between 62-95 and 45-75%, respectively. In addition, removal efficiencies of sulfide (96-99%) and COD (50-80%) were obtained by using Fe(2+) ions together with Ca(OH)(2) as precipitant-aid under the same conditions. In experiments performed with raw wastewater which had different pH values, COD removal efficiencies of Fe(3+) and Fe(2+) ions together with Ca(OH)(2), were 50-80 and 32-50%, respectively.