Systems and methods for compact, decentralized desalination of feedwater for point-of-use applications

A method of operating a desalination system, comprising:

• flowing a fluid through a conduit network through at least one reverse osmosis element, the conduit network having at least a loop and a permeate branch;
• recirculating a fluid that exits the at least one reverse osmosis element through the loop and back into the at least one reverse osmosis element, the fluid flowing through a pump that is disposed within the loop;
• sending a signal to a second pump to adjust one or more of a pressure, a flow speed, or a volumetric flow rate of the fluid that is output by the second pump, and
• adjusting the signal based on an amount of accumulation of salinity in the at least one reverse osmosis element,
• wherein a flow rate through the pump is in the range of 50 liters per hour to 200 liters per hour.

A fluid desalination system, comprising:

• at least one reverse osmosis element having an inlet and an outlet;
• a conduit network that comprises a loop and a permeate branch, the loop being in fluid communication with the at least one reverse osmosis element to convey fluid passed through the at least one reverse osmosis element from the respective outlets of each of the at least one reverse osmosis elements to the respective inlets of each of the at least one reverse osmosis elements so the fluid enters at least one of the at least one reverse osmosis elements again, and the permeate branch being in fluid communication with the at least one reverse osmosis element to receive fluid that has been desalinated by the at least one reverse osmosis element;
• and
• a first pump disposed within the loop and configured to move the fluid from the respective outlets of each of the at least one reverse osmosis elements and towards the respective inlets of each of the at least one reverse osmosis elements the first pump having one or more one-way check valves disposed therein;
• a second pump configured to introduce fluid into at least one of the loop and the at least one reverse osmosis element;
• a control system configured to supply a pulse width modulation signal to the second pump to control at least one of a flow speed or a volumetric flow rate of the fluid introduced by the second pump into at least one of the loop and the at least one reverse osmosis element,
• wherein the loop is devoid of a one-way valve that is separately disposed from the first pump, and wherein the controller is configured to control the second pump based on accumulation of salinity in the at least one reverse osmosis element.