Method for preparing water quality profile, method for inspecting separation membrane module, and water treatment apparatus

A method of inspecting a separation membrane module, the method comprising:

• (1) step 1 of obtaining permeates by feeding a water-to-be-treated to a separation membrane module comprising a water-to-be-treated feed port and a plurality of permeate outlets, the plurality of permeate outlets comprising a first permeate outlet and a second permeate outlet, the first permeate outlet connected to the second permeate outlet to form an open channel;
• (2) step 2 of changing a ratio between flow rates of the respective permeates flowing out through the plurality of permeate outlets, step 2 further comprising changing a first flow rate of permeates flowing out of the first permeate outlet and a second flow rate of permeates flowing out of the second permeate outlet, the first flow rate being controlled by a first flow rate control valve and the second flow rate being controlled by a second flow rate control valve;
• (3) step 3 of measuring water qualities of the respective permeates after the step 2;
• and
• (4) step 4 of plotting a relation between the ratio between the flow rates of the respective permeates, which was changed in the step 2, and the water qualities of the respective permeates, which were measured in the step 3, as a scatter diagram, and
• repeatedly performing the steps 2 to 4 several times and from a width over which a water quality fluctuates at an inflection point of the scatter diagram, a number of the inflection points which appear in the scatter diagram, or a position of each of the inflection points of the scatter diagram, detecting a presence or absence of an abnormality in the separation membrane module, a degree of the abnormality, or a location where the abnormality occurred.