Patent ID: 8123833

Claim:
A process for producing a gas-containing cleaning water which contains a specific gas dissolved in water, which process comprises (i) dissolving the specific gas into a material water containing other gases than the specific gas present in the water under an increased pressure exceeding an atmospheric pressure to prepare a gas-containing water having a concentration of the specific gas exceeding the solubility of the specific gas under an atmospheric pressure and, then, (ii) removing a portion of the dissolved gases to remove the portion of the dissolved gases exceeding the concentration of saturation by decreasing pressure on the gas-containing water to a pressure in the range of ±20% of the atmospheric pressure by passing the gas-containing water having a concentration of the specific gas exceeding the solubility of the specific gas under an atmospheric pressure through a gas permeation membrane module, a gaseous phase portion of which is opened to the atmosphere or is connected to the atmosphere in a manner such that there is no pressure loss.