Abstract Two new distillation plants are going into operation in Italy. The first, located in the town of Bari, is an high temperature multi-stage flash, with production rate of l700 m 3/d, top brine temperature of 150°C and performance ratio of 19 kg fresh water per kg steam. The second is a vapor-compression, vertical tube evaporator, with a 240 m 3/d production rate at 105°C and electric energy consumption of 14 kWh/m 3. These plants are coupled with an ion exchange pretreatment unit, where bicarbonates and sulfates are partially exchanged with chlorides by means of a weak anion resin regenerated with brine; alkaline (CaCO 3, Mg(OH) 2) and sulfate (CaSO 4) scales are thus prevented from occurring. The two plants have been designed on the basis of extensive evaluations on pilot and laboratory-scale plants briefly described hereafter. The research development includes studies on a combination of hydrolysis and direct exchange Cl -/HCO - 3, with the final aim of dealkalizing sea water without fresh acid consumption.