Desalters are also used to treat groundwater reservoirs in areas impacted by cattle feedlots and dairies.
The salts that are most frequently present in crude oil are calcium, sodium and magnesium chlorides.
The high temperatures that occur downstream in the process could cause water hydrolysis, which in turn allows the formation of corrosive hydrochloric acid.
Crude oil to be desalted is heated to a temperature of 100-150 °C and mixed with 4-10% fresh water, which dilutes the salt.
An electrostatic field is applied by electrodes in the settling tank, inducing polarization of the water droplets floating in the larger volume of oil.