Flow control for reverse osmosis filter

A system for water filtration, comprising:

• a reverse osmosis filter having a semipermeable membrane;
• a feed line, a permeate line, and a concentrate line, each in fluid communication with the filter;
• a pump at the feed line pumping feed water into the filter;
• a flow sensor configured to monitor a flow rate of permeate water exiting the filter into the permeate line;
• a permeate sensor configured to monitor a property of the permeate water;
• an adjustable valve configured to regulate a flow rate of concentrate water exiting the filter into the concentrate line;
• and
• a pressure sensor configured to detect a pressure that correlates with permeate water flow;
• and
• at least one controller configured to control:
• a first feedback circuit configured to 1) compare the flow rate of the permeate water with a target flow rate of the permeate water and 2) calculate a reference pressure based on a difference between the flow rate of the permeate water and the target flow rate of the permeate water,
• wherein the flow rate of the permeate water is based on at least the pressure of the feed line;
• a second feedback circuit configured to 1) compare the pressure from the pressure sensor to the reference pressure calculated by the first feedback circuit and 2) regulate a flow rate of the feed water to adjust a pressure of the feed line towards the reference pressure calculated by the first feedback circuit,
• wherein the second feedback circuit operates at a higher frequency than at least the first feedback circuit;
• and
• a third feedback circuit configured to regulate the flow rate of the concentrate water exiting the filter into the concentrate line based on the property monitored by the permeate sensor.