New fouling prevention method using a plasma gliding arc for produced water treatment

• New plasma-based method is introduced to prevent mineral fouling in produced water.
• Plasma arc discharge removed bicarbonate ions in produced water.
• CaCO3 fouling was prevented in heat transfer surface with zero bicarbonate ions.
• Excessively high Ca2 + ions in water did not cause CaCO3 fouling problem.

The objectives of the present study were to test a new plasma-based method for bicarbonate removal in water produced from hydraulic fracturing for shale gas and to verify bicarbonate removal as a mechanism for mineral fouling prevention. The study employed dual hypotheses: (1) gliding arc plasma can reduce bicarbonate concentration of produced water to negligible levels, and (2) water without bicarbonate content is unable to cause mineral fouling in the form of calcium carbonate scale even in the presence of extremely high concentrations of calcium ions as is often found in produced water. The plasma treatment of produced water reduced the concentration of bicarbonate ions from a range of 684–778 ppm to zero. Subsequently, heat transfer fouling tests were conducted with water samples, where the concentration of bicarbonate ions varied from 0 to 500 ppm with a fixed concentration of calcium ions of 5000 ppm. The weight of mineral scale that accumulated on a heating element over time was determined. The present test results showed that no fouling was formed over 30 h on the heating element in the water without bicarbonate ions. This proof-of-concept study demonstrated that plasma treatment is capable of reducing the concentration of bicarbonate ions in produced water to a level where CaCO3 fouling can be prevented on a heat transfer surface. The plasma gliding arc may represent a new non-chemical fouling prevention method for the treatment of produced water.