Abstract: The majority of oilfields have now progressed to secondary or tertiary recovery stages. Water and gas injection serve as primary measures to replenish reservoir energy and enhance recovery rates. Re-injected water from oilfields invariably contains substantial ferrous ions. Current wastewater treatment processes and equipment — typically employing oil removal, flotation and filtration — struggle to adequately remove these iron ions, thus affecting the quality of the reinjection water. Based on on-site application tests conducted at the Ningyi Station of Liaohe Oilfield's Qingyang Project Department, hydrogen peroxide was integrated into an inorganic flocculant and the composite concentration was optimized. This approach achieved excellent results in removing iron ions from the wastewater.

Key words: oilfield wastewater, iron ions, suspended solids (SS), hydrogen peroxide