Forward osmotic and water hammer method of membrane cleaning

A method for a multiple-phase pressure retarded osmosis (PRO) process, the method comprising:

• performing an energy generation phase;
• performing a flushing phase subsequent to completion of the energy generation phase;
• and
• repeating at least one more additional energy generation phase subsequent to completion of the flushing phase,
• wherein the energy generation phase comprises:
• continually introducing a first portion of draw solution into a high pressure compartment of a PRO module, the first portion of the draw solution contacting a first side of a semi-permeable membrane disposed within the PRO module;
• introducing a low salinity solution having lower salinity than the draw solution into a low pressure compartment of the PRO module, the low salinity solution contacting a second side of the semi-permeable membrane that is opposite the first side, to generate a mixture of the first portion of the draw solution and the low salinity solution;
• and
• expelling the mixture from the PRO module, and
• wherein the flushing phase comprises:
• adding an additional solution to the draw solution, to reduce osmotic pressure of the draw solution and generate a reverse movement of water from a higher gauge pressure area, the reverse movement flushing away salt that has accumulated on the semi-permeable membrane.

A system for a multiple-phase pressure retarded osmosis (PRO) process, comprising:

• at least one module for performing the multiple-phase PRO process, the at least one module divided by at least one semi-permeable membrane into at least one high-pressure compartment and at least one low-pressure compartment;
• a source of draw solution;
• a source of additional solution;
• a source of low salinity solution, the low salinity solution being of lower salinity than the draw solution;
• and
• an energy generation device for converting a high-pressure fluid flow into energy,
• wherein the at least one high-pressure compartment comprises a first set of inlets and a first set of outlets,
• wherein the at least one low-pressure compartment comprises a second set of inlets and a second set of outlets,
• wherein at least one inlet in the first set of inlets is fluidly connected to the source of draw solution and/or to the source of additional solution,
• wherein at least one outlet in the first set of outlets is fluidly connected to the energy generation device,
• wherein at least one inlet in the second set of inlets is fluidly connected to the source of low salinity solution,
• wherein at least one outlet in the second set of outlets is fluidly connected to a drain.