Evaluation of operational parameters and technology readiness for enhanced management of oilfield produced water treated by ozonation

Abstract

Managing oilfield produced water (OPW) is a significant challenge for the petrochemical industry due to the high daily volumes generated and strict disposal limits for oil and grease (O&G) content. O&G levels are influenced by organic compounds known as naphthenic acids (NAs). This study explored ozonation to degrade cyclohexane carboxylic acid (CHCA, a model compound for NAs) present in a synthetic OPW matrix and reduce O&G in real OPW from offshore platforms. Experiments were conducted on four ozonation prototypes with varying effluent capacities: a simplified bench-scale prototype (200 mL), an extended bench-scale prototype (400 mL to 800 mL), a hydrodynamic cavitation reactor with Venturi (5 L), and a pilot unit reactor (25 L to 80 L). CHCA degradation ranged from 91 % to 100 % under optimized conditions for each prototype. Additionally, the ozonation treatment met the Brazilian National Environment Council’s disposal requirements for OPW in oceanic regions, achieving an O&G content below 29 mg/L within 30 min at natural pH. The energy required for degradation (ERC) decreased from 729.2 kWh/m3 to 30.3 kWh/m3 as ozonation scaled up from the simplified bench-scale system (200 mL) to the pilot scale (80 L). For real OPW, the ERC was even lower at 34.5 kWh/m3. These findings demonstrate the effectiveness of ozonation in treating OPW and underscore the importance of multi-scale studies to evaluate the technical and economic viability of this treatment technology. This contributes to the sustainable management of industrial waste even in space-restricted installations such as offshore oil production facilities.