Wastewater treatment in Oil & Gas sector

Further development of wastewater treatment in the oil and gas sector

Advanced electrochemical oxidation with boron-doped diamond (BDD AEOP)

The oil and gas industry is facing growing challenges in wastewater treatment. Upstream and downstream processes generate complex wastewater streams that contain large quantities of hydrocarbons, heavy metals and persistent organic substances. Processes such as biological or chemical-physical treatment are reaching their limits. Although activated carbon and ion exchange are effective, they incur high operating costs.

The DiOx system from PPU Umwelttechnik GmbH offers an innovative solution with electrochemical oxidation (AEOP) on boron-doped diamond (BDD). This article examines the challenges of wastewater treatment, the limitations of existing technologies and the advantages of the DiOx BDD AEOP. It uses case studies of frac flowback water and caustic treatment in refineries to illustrate the potential of this technology.

Module ClearFox®DiOx 1.0 used for the oil and gas industry

Wastewater in the oil and gas industry

Challenges in the upstream sector

Upstream processes such as hydraulic fracturing (fracking) and crude oil production generate highly contaminated wastewater. Frac flowback water contains high levels of dissolved salts (>180,000 mg/l), hydrocarbons, heavy metals such as barium and arsenic as well as organic compounds such as benzene, toluene, ethylbenzene and xylenes (BTEX). It also contains residues of fracking chemicals, biocides and radioactive substances (NORM). The variable composition makes biological treatment methods almost impossible. Physical processes such as dissolved air flotation (DAF) cannot remove dissolved pollutants.

Challenges in the downstream sector

Refineries and petrochemical plants produce wastewater with a high chemical oxygen demand (COD) of 20,000 to 300,000 mg/litre. Leach streams contain sulphides, mercaptans and phenolic compounds. They have a pH value of over 12 and high temperatures, which makes treatment more difficult. Wet air oxidation (WAO) systems are effective but can cause high operating costs and reach capacity limits.

Limits of conventional technologies

Physical and biological methods

Processes such as DAF and ceramic microfiltration remove particles and emulsified oils, but fail when it comes to dissolved organic and inorganic pollutants. Biological systems are cost-effective, but cannot be used in many types of wastewater due to the high salt content and toxic components.

High costs of advanced processes

Activated carbon and ion exchange systems require frequent media changes. This leads to high costs and generates secondary waste. Reverse osmosis (RO) clogs up when the salt content is high, making complex pre-treatment necessary.

ClearFox® DiOx boron-doped diamond electrodes

The DiOx BDD AEOP system: mechanism and advantages

Technology overview

The DiOx system uses boron-doped diamond electrodes to generate hydroxyl radicals (· OH) through water electrolysis. These radicals oxidise organic pollutants to CO₂ and H₂O and convert inorganic compounds such as sulphides into sulphates. The most important components are:

BDD electrodes: Resistant to corrosion and fouling
Modular reactors: Customisable stacks with flow rates from 0.5 to 500 m³/day
Automated control systems: Real-time monitoring of pH value, conductivity and redox potential

Advantages compared to other methods

No use of chemicals: In contrast to ozonation or Fenton processes, no additives are required.
High efficiency: Removes >95 % of COD, including PFAS and dioxins.
Sludge-free operation: No secondary sludge, lower disposal costs.

Case studies

Frac flowback water in Saudi Arabia

Pre-treatment with ceramic membranes removed 99 % of the solids, oils and bacteria. However, the COD remained at 2,000 mg/l. The subsequent DiOx treatment reduced this to <100 mg/l. BTEX compounds were no longer detectable. The oxidation was fully controllable, only the duration varied.

Leach streams in refineries

Refineries in the Middle East have capacity problems with WAO systems. A test with DiOx showed that >90 % of the sulphides were converted to sulphates and COD was reduced by >85 %. This enabled safe biological post-treatment. Energy consumption was lower than with WAO, which reduced operating costs. In addition, there was no need for high-pressure reactors, which increased safety.

ClearFox® oil & gas wastewater treatment system in Saudi Arabia

Synergies with ceramic membranes

A combination of membrane filtration and DiOx improves process performance. Membranes remove solids that could contaminate the electrodes, while DiOx breaks down dissolved organic pollutants. This combination is particularly suitable for frac water.

Advantages of DiOx

Modular scalability: Containerised units can be used in remote oil fields.
High adaptability: Handles variable inflows without loss of efficiency.
Compliance with strict environmental regulations: Complies with limit values for heavy metals (<0.1 mg/l arsenic) and hydrocarbons.

Conclusion

PPU Umwelttechnik GmbH utilises DiOx systems in various projects. Cooperations with waste disposal and service companies promote integration into existing water management systems.

The DiOx BDD AEOP system is revolutionising wastewater treatment in the oil and gas industry. It overcomes the weaknesses of conventional technologies by working without chemicals or secondary waste and completely degrading even persistent pollutants. The increasing demand for water reuse and Zero Liquid Discharge (ZLD) will continue to drive the adoption of DiOx, transforming wastewater from a liability into a valuable resource.

Treating more wastewater for less money