I have a question regarding desalter brine quality, as follows: The desalting of same crude is done by two desalters of different geometry (not two stage desalting, two CDUs). I underline that desalting is done efficiently in both units with respect to salt content in desalted crude. The difference is in the content of sulfides in desalter brine. The desalter that has lower sulfide content in brine is more cylindrical, while the another one "tends to be more spherical". The higher sulphide content represents higher load for waste water treatment plant. My opinion is that this behaviour can occur because of longer residence time of oil and wash water in emulsion volume (or the volume ratio of emulsion volume and total desalter volume). I think that perhaps the emuslifier dossage or or delP on mixing valve are higher. Has anybody faced similar issue in the refinery? Any opinion and experience would be helpful.