A method comprising: - mixing a crude oil stream comprising brine with a wash water stream to form an emulsion of wash water in crude oil; - flowing the emulsion to a desalter ; - in the desalter: - coalescing the wash water to reform the wash water stream and to transfer at least a portion of the salt from the crude oil stream to the wash water stream, and; - separating a crude oil stream with reduced salt content from a desalter effluent comprising the wash water stream to which at least the portion of the salt is transferred; - flowing said desalter effluent to a processing unit ; - in the processing unit : - processing the desalter effluent to form a processed effluent having a concentration of salt which is equal to or less than a concentration of salt in a fresh water stream (180, said fresh water stream having a lower salt content than the brine in the crude oil stream ; - recycling at least a portion of the processed effluent and mixing it and the fresh water stream with the crude oil stream before flowing the emulsion to the desalter. - mixing a crude oil stream comprising brine with a wash water stream to form an emulsion of wash water in crude oil; - flowing the emulsion to a desalter ; - in the desalter: - coalescing the wash water to reform the wash water stream and to transfer at least a portion of the salt from the crude oil stream to the wash water stream, and; - separating a crude oil stream with reduced salt content from a desalter effluent comprising the wash water stream to which at least the portion of the salt is transferred; - flowing said desalter effluent to a processing unit ; - in the processing unit : - processing the desalter effluent to form a processed effluent having a concentration of salt which is equal to or less than a concentration of salt in a fresh water stream (180, said fresh water stream having a lower salt content than the brine in the crude oil stream ; - recycling at least a portion of the processed effluent and mixing it and the fresh water stream with the crude oil stream before flowing the emulsion to the desalter. - coalescing the wash water to reform the wash water stream and to transfer at least a portion of the salt from the crude oil stream to the wash water stream, and; - separating a crude oil stream with reduced salt content from a desalter effluent comprising the wash water stream to which at least the portion of the salt is transferred; - flowing said desalter effluent to a processing unit ; - in the processing unit : - processing the desalter effluent to form a processed effluent having a concentration of salt which is equal to or less than a concentration of salt in a fresh water stream (180, said fresh water stream having a lower salt content than the brine in the crude oil stream ; - recycling at least a portion of the processed effluent and mixing it and the fresh water stream with the crude oil stream before flowing the emulsion to the desalter. - processing the desalter effluent to form a processed effluent having a concentration of salt which is equal to or less than a concentration of salt in a fresh water stream (180, said fresh water stream having a lower salt content than the brine in the crude oil stream ; - recycling at least a portion of the processed effluent and mixing it and the fresh water stream with the crude oil stream before flowing the emulsion to the desalter. <EOS>