Abstract: An inventive apparatus for closed circuit batch-RO desalination comprising a RO-skid with membrane elements and circulation means for the recycling of RO concentrate through membranes and a designed hydraulic-arm with a disc separating between a section of pressurized hydraulic fluid created by a high pressure hydraulic pump under fixed flow and variable pressure conditions and a section of RO recycled concentrates. The batch desalination sequence is completed when the entire hydraulic-arm volume is filled with hydraulic fluid and thereafter, desalination is stopped, said apparatus decompressed, brine removed and hydraulic-arm recharged with fresh feed before the initiation of a new batch sequence. The inventive apparatus enables RO desalination under the lowest energy and highest recovery prospects not possible by any other RO technique.

Abstract: The retrofit technology utilizes pressurized brine of convention RO to feed a Closed Circuit Desalination (CCD) unit; wherein, further desalination takes place to a desired recovery level. The application exemplified in FIG. 4 is of a retrofit unit comprising a Booster Pump (BP2) for raising pressure of inlet feed; a Circulation Pump (CP) for creating cross flow over membranes (E) in the pressure vessel (M), thereby enable efficient RO desalination; an Actuated Valve (AV) in line with a partially open Manual Valve (MV) to enable periodic replacement of high salinity concentrates with fresh feed without stopping desalination; No Return (NR) valve means to control the direction of flow in the system; and monitoring means such as of electric conductivity (CM) and flow (FM). Periodic replacement of high salinity concentrates by fresh feed initiated at desired high system electric conductivity and terminated at a desired low system electric conductivity, while desalination continued.