Desalination of oilfield produced waters via reverse electrodialysis: A techno-economical assessment

Produced waters (PWs) are oilfield waste streams rich in minerals and hydrocarbons whose production rate is largely increased in last decades following the corresponding increase of energy demand. The high salinity level of PWs inhibits the adoption of cheap biological treatments. Also, desalination techniques based on osmotic membranes would require severe pre-treatments. As an alternative, Reverse ElectroDialysis (RED) and Assisted Reverse ElectroDialysis (ARED) are here proposed for the first time to reduce the salinity level of PWs. RED may also guarantee an operation cost reduction thanks to its energy generation. An ad-hoc model for RED and ARED is here developed in order to deal suitably with PWs. This is done by a calibration and validation with experimental data purposely collected via RED and ARED units fed by real PWs. The model is integrated with economical equations and a techno-economic analysis is carried out in order to identify the best configuration for the desalination purposes. Results suggest that ARED operation mode is the best option guaranteeing a minimum in the controlled dilution cost corresponding to a 1.32 € per m3 of PWs treated, thus leaving room for an affordable future implementation of more sophisticated treatment chains based on bioremediation.