Water purification apparatus, system and method for controlling at least one fluid property

A water purification apparatus comprising:

• a reverse osmosis device configured to produce purified water, the reverse osmosis device including a feed inlet positioned to receive feed water and a purified water outlet;
• a reverse osmosis pump configured to pump feed water to the feed inlet;
• a recirculation path configured to recirculate a proportion of the purified water from a first point downstream from the reverse osmosis device to a second point upstream of the reverse osmosis device;
• a purified water path configured to transport purified water from the purified water outlet to a destination, wherein the purified water path includes (i) a permeate water path positioned upstream of the recirculation path, and (ii) a product water path positioned downstream from the recirculation path to transport product water to the destination, wherein the permeate water path splits into the recirculation path and the product water path at the first point;
• a flow sensor configured to detect a flow rate of purified water in the permeate water path;
• a control unit configured to control the reverse osmosis pump to a certain pump rate corresponding to a certain flow rate of purified water through the permeate water path;
• a heater positioned downstream from the reverse osmosis device to heat the purified water flowing in the purified water path;
• a temperature sensor positioned to measure a temperature of the purified water immediately downstream from the heater, wherein the control unit is configured to control the temperature of feed water flowing through a reverse osmosis membrane of the reverse osmosis device based on the temperature detected by the temperature sensor, and
• a tank configured to receive water from an external water source and to provide feed water to the feed inlet of the reverse osmosis device, wherein the tank includes an air vent line extending from an upper portion of the tank.

A peritoneal dialysis system comprising:

• a water purification apparatus including
• a reverse osmosis device configured to produce purified water, the reverse osmosis device including a feed inlet positioned to receive feed water and a purified water outlet,
• a reverse osmosis pump configured to pump feed water to the feed inlet,
• a recirculation path configured to recirculate a proportion of the purified water from a first point downstream from the reverse osmosis device to a second point upstream of the reverse osmosis device,
• a purified water path configured to transport purified water from the purified water outlet to a destination, wherein the purified water path includes (i) a permeate water path positioned upstream of the recirculation path, and (ii) a product water path positioned downstream from the recirculation path to transport product water to the destination, wherein the permeate water path splits into the recirculation path and the product water path at the first point,
• a flow sensor configured to detect a flow rate of purified water in the permeate water path, and
• a control unit configured to control the reverse osmosis pump to a certain pump rate corresponding to a certain flow rate of purified water through the permeate water path,
• a heater positioned downstream from the reverse osmosis device to heat the purified water flowing in the purified water path,
• a temperature sensor positioned to measure a temperature of the purified water immediately downstream from the heater, wherein the control unit is configured to control the temperature of feed water flowing through a reverse osmosis membrane of the reverse osmosis device based on the temperature detected by the temperature sensor, and
• a peritoneal dialysis (“PD”) cycler positioned and arranged to use PD fluid during a PD treatment, the PD fluid mixed using product water from the water purification apparatus.

A method for controlling at least one fluid property in a water purification apparatus, the water purification apparatus including a reverse osmosis device configured to produce purified water, a reverse osmosis pump configured to pump feed water, and a recirculation path arranged to recirculate a proportion of the purified water from a first point downstream from the reverse osmosis device to a second point upstream of the reverse osmosis device, the method comprising:

• arranging a purified water path to include (i) a permeate water path positioned upstream of the recirculation path and (ii) a product water path positioned downstream from the recirculation path;
• splitting the permeate water path into the recirculation path and the product water path at the first point;
• controlling the reverse osmosis pump to a certain pump rate corresponding to a certain flow rate of purified water through the permeate water path;
• monitoring a temperature sensor positioned immediately downstream of a heater to detect a temperature of the purified water;
• and
• controlling the temperature of water flowing through a reverse osmosis membrane of the reverse osmosis device based on the temperature detected by the temperature sensor.