Treatment of Water-soluble Organics in Produced Water

Fig. 1. Electrostatic spraying can generate a fine mist of bubbles in water

Helping industry solve problems

Produced water is generated in oil production, and treatment is especially difficult for off-shore deep-water operations. Existing physical treatment technologies used to remove dispersed oil from produced water will not remove soluble organics. Gulf of Mexico (GOM) operations are rapidly moving towards design of large, expensive, high-capacity platforms that will require compact, low-cost, efficient treatment processes to comply with current and future water quality regulations.

Previous studies performed by the Petroleum Environmental Research Forum (PERF) demonstrated that ozone treatment reduces the level of napthenic acids in GOM produced water. However, the treatment efficiencies were limited.

The goal of Oak Ridge National Laboratory’s project is to maximize oxidation of water-soluble organics during a single-pass operation. The project investigates:
1. ozone production by electrochemical methods,
2. increasing the mass transfer rate in the reactor by forming microbubbles during ozone injection into the produced water,
3. sonochemical generation of hydrogen peroxide in water, and
4. using ultraviolet oxidation for catalytic oxidation to enhance the oxidation reactions if needed.

Fig. 2.The sonochemical generation and the destruction of organics can be tested in an experimental apparatus

Electrochemical generation of ozone has the advantages of being much more efficient than standard corona-discharge techniques, is very compact and easy to operate and maintain, and only requires water and electricity as raw materials. It would, therefore, be ideal for use in off-shore applications. Dispersers or inverse electrostatic spraying (above) can be used to spray ozone-containing gas into the aqueous solution to generate microbubbles for enhancing the mass transfer rate into the liquid phase.

Sonochemical production if hydrogen peroxide is an ultrasonic wave in liquid that generates cavitation bubbles. The implosion and break-up of these bubbles results in extremely localized temperature, pressure, and electrochemical fluctuations. The phenomenon causes water to fractionate into radical species (H•, •OH, HOO•) that rapidly reacts with compounds in solution. The combination of certain radicals also results in the formation of H₂O₂, a powerful oxidant used in wastewater treatment. The efficiency of radicals generation is dependent on the sound frequency.

For further information contact:

Thomas Klasson, Ph.D.
e-mail: klassonkt@ornl.gov

Updated 05/00
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