Efficient Removal of Dissolved Organics and Naphthenic Acids from Offshore Produced Water: Performance and Challenges of an Electrochemical Pilot Plant
Daniela Gier Della Rocca, Silvio Edegar Weschenfelder, Marta Cordeiro da Fonseca, Glaucia Rodrigues Vieira de Almeida da Fonseca, Luciana Prazeres Mazur, Sálvio Lima de Carvalho Neto, Adriano da Silva, Débora de Oliveira, Regina F. P. M. MoreiraAbstract
Oilfield produced water (OPW) is a complex wastewater, including recalcitrant compounds and stable emulsions. Although electrochemical treatment has shown promising laboratory-scale results for treating this effluent, pilot-scale validation and scale-up remain poorly explored. Therefore, this study investigates the treatment of real offshore OPW using two electrochemical pilot plants (6 and 15 L). Under the optimum operating conditions (25 A·m–2 and a residence time of 4 min), the process reduced total oil and grease from 152 to 3 mg·L–1, turbidity from 69.4 to 1.0 NTU, and total organic carbon from 561 to 42 mg·L–1. In addition, the larger pilot unit achieved similar or improved performance, confirming the feasibility of process scale-up. The results indicate that electrocoagulation/flocculation and electro-oxidation occurred simultaneously, promoting the rapid removal of dissolved organic compounds and anodic transformation of the naphthenic acids. Practical aspects relevant to offshore implementation, including energy demand (7.8 kWh kg of TOG removed–1), heat generation (166 W), gas evolution (13.5 L·h–1), and process footprint (10 m·h–1 and 15 h–1), are also discussed, highlighting the feasibility of industrial implementation.