This paper presents the results of a successful field trial using electrocoagulation and reverse osmosis to desalinate oilfield produced water for surface discharge and beneficial reuse near Bakersfield, California. The paper discusses technology selection, pilot test configuration, test results, projected operating costs and reliability, and conclusions.
The field trial was conducted at an oilfield wastewater facility where up to 10,000 barrels per day of produced water containing 3,700 mg/L of TDS (total dissolved solids) was being treated in a series of un-lined ponding basins to remove free oil and solids, and then used to irrigate an area containing salt-tolerant grasses, shrubs, and trees. Due to concerns that local groundwater might be impacted, in 2016 the operator was given two years by regulators to substantially reduce the salt, aromatic hydrocarbon, and boron content of the water, or cease surface discharge.
After a detailed review of options, the operator elected to conduct a 60-day pilot test of a process that consisted primarily of electrocoagulation followed by reverse osmosis to desalinate the produced water and remove aromatic hydrocarbons. Boron removal would be accomplished by use of a boron-specific anion exchange resin downstream of the reverse osmosis membranes.
The pilot treatment system would be designed and installed to comply with the local Regional Water Quality Control Board specifications for surface discharge, herein collectively called the "Effluent Specifications" (Table 1).
In July 2016, the operator started the 60-day pilot test. After an initial commissioning period, the facility demonstrated the ability to safely and reliably treat the produced water to below the limits contained in the Effluent Specifications.
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