Working medium and water treatment system

A water treatment system comprising:

• an osmotic pressure generator;
• and
• a concentrator,
• the osmotic pressure generator comprising:
• a first chamber configured to accommodate water to be treated;
• a second chamber configured to accommodate a working medium and comprising the working medium;
• an osmosis membrane configured to partition the first chamber and the second chamber;
• a treatment container configured to accommodate the first chamber, the second chamber and the osmosis membrane, and
• the concentrator comprising:
• a carbon dioxide releasing unit configured to release carbon dioxide from the working medium;
• a phase separating unit configured to phase-separate the working medium;
• and
• carbon dioxide introducing unit configured to cause the working medium to absorb carbon dioxide,
• wherein the water treatment system further comprises:
• first inlet pipeline configured to introduce water to the first chamber;
• a second inlet pipeline configured to introduce the working medium to the second chamber;
• an outlet pipeline configured to deliver diluted working medium from the second chamber of the osmotic pressure generator to the concentrator,
• and wherein the working medium comprises:
• a first amine compound;
• and
• a second amine compound,
• wherein the first amine compound is a heterocyclic tertiary amine compound which consists of a carbon atom, a nitrogen atom and a hydrogen atom, and in which a ratio (C/N ratio) of a carbon atom number to a nitrogen atom number included in one molecule is from 7 to 9, the heterocyclic tertiary amine compound comprising a plurality of heterocycles,
• the first amine compound comprises at least two tertiary amino groups comprising heterocycles, and
• the second amine compound is a heterocyclic tertiary amine compound which consists of a carbon atom. a nitrogen atom and a hydrogen atom, and in which a ratio (C/N ratio) of a carbon atom number to a nitrogen atom number included in one molecule is in a range of 5 or more to less than 7, the heterocyclic tertiary amine compound comprising a plurality of heterocycles.