Water filtration system

A water filtration system, comprising:

• a filter cartridge assembly, wherein the filter cartridge assembly is an integrated composite filter cartridge that has a water inlet for receiving raw water, a purified-water outlet for dispensing purified water that is produced by the integrated composite filter cartridge through a first filtering process, a purified-water return port for receiving at least some of the purified water that is dispensed from the purified water outlet, a pure-water outlet for dispending pure water that is produced by the composite filter cartridge that is produced by the integrated composite filter cartridge through a second filtering process distinct from the first filtering process and a waste discharge port for dispensing waste water that is produced with the pure water by the integrated composite filter cartridge through the second filtering process;
• a water-intake pipe communicated with the water inlet;
• a purified-water pipeline configured to connect the purified-water outlet to the purified-water return port, the purified-water pipeline being provided with a purified-water external port and a first valve configured to control on and off of the purified-water pipeline;
• a pure-water pipeline communicated with the pure-water outlet, the pure-water pipeline being provided with a pure-water external port and a second valve configured to control on and off of the pure-water pipeline;
• a waste discharge pipeline having a first end communicated with the waste discharge port and a second end communicated with an outside;
• and
• a circulation pipeline having a first end communicated with the purified-water pipeline and a second end communicated with the waste discharge pipeline,
• wherein when the water filtration system produces the purified water using the first filtering process of the integrated composite filter cartridge, the purified-water pipeline is on and the pure-water pipeline is off;
• when the water filtration system produces the pure water using the second filtering process of the integrated composite filter cartridge, the purified-water pipeline, the pure-water pipeline and the waste discharge pipeline are on respectively.