A method for reducing accumulation of foulants on reverse osmosis membranes and a groundwater desalination system

A groundwater desalination system, the system comprising:

• a production borehole casing disposed, in use, in a production borehole or well, the production borehole casing being adapted for ingress of groundwater therein;
• a water treatment system comprising one or more reverse osmosis units having respective reverse osmosis membranes, the water treatment system being adapted to treat a groundwater stream and thereby produce a permeate stream having a lower concentration of dissolved solids than the groundwater stream and a concentrate stream having a higher concentration of dissolved solids than the groundwater stream;
• one or more reinjection boreholes spaced apart from the production borehole, the one or more reinjection boreholes being adapted to receive the concentrate stream produced by the water treatment system;
• a pump for passing the groundwater stream through the water treatment unit, the pump being provided with a variable speed drive to vary a pressure of the groundwater stream between a first feed pressure and a second feed pressure, wherein the first feed pressure is greater than an osmotic pressure of the ground water by an amount sufficient to establish reverse osmosis at the reverse osmosis membranes and the second feed pressure is less than the osmotic pressure of the ground water, thereby generating a forward osmosis backflow of the permeate stream through said reverse osmosis membranes into the groundwater feedstream and dislodging foulants from said reverse osmosis membranes;
• a filter configured to filter the dislodged foulants from the resulting mixture of backflow and groundwater;
• and
• a concentrate conduit configured to transport the concentrate produced from the water treatment system to the one or more reinjection boreholes;
• wherein the one or more reinjection boreholes are provided, respectively, with a reinjection borehole casing and a seal positionable within the reinjection borehole to limit mixing and reaction between the concentrate and oxygenated water in the reinjection borehole.