Demonstration of Dissolved Organics Removal from Produced Water

The biological GAC-FBR process is a high rate treatment system for economically degrading dissolved organics, such as benzene, aromatic and aliphatic hydrocarbons, and organic acids at high rates and short residence times. In many instances, removal of water soluble organics, after deoiling, is sufficient for meeting surface discharge of produced waters. At other sites, a reduction in the TDS concentration will be necessary prior to meeting surface discharge requirements. Results of a field demonstration in Wyoming (up to 350 bbl/day) where a treatment train consisting of deoiling, followed by removal of water soluble organics using the GAC-FBR are presented. Because of a high concentration of organic acids present in this water, a two-stage FBR system consisting of sequential anoxic and aerobic treatment was used to treat produced water from this site. Consistent removal of organics was observed even during periods when the up-front deoiling was not operating properly. Effluent O&G of less than 5 mg/L was consistently achieved with an O&G concentration of 53 mg/L after induced gas flotation. Most organics (i.e., BTEX, acetate) were removed to near or below detection limits. Based on the results obtained, costs for organics removal (deoiling followed by the GAC-FBR for water soluble organics removal) were estimated for 4000 barrels per day of produced water. The total cost, including 10-year amortization of capital, was estimated to be $0.068 per barrel. O&M costs for a single-stage aerobic treatment system were approximately $0.02 per barrel.