State diagnosis method for separation membrane element

A non-transitory computer-readable recording medium storing a state diagnosis program for a separation membrane element, the program causing, in order to execute state diagnosis of a separation membrane element for obtaining a permeate from a water-to-be-treated, a computer to function as:

• a data input unit configured to input data of the separation membrane element of at least any of a pressure, a flow rate, and a solute concentration of the water-to-be-treated, at least any of a pressure, a flow rate, and a solute concentration of the permeate, and a measured permeate quality obtained by a measurement of a permeate quality by passing through a tube having an outer diameter smaller than an inner diameter of a permeate channel to the permeate channel to sample the permeate of different locations at at least two measurement locations and measuring the permeate quality;
• a membrane separation performance initial value calculation unit configured to calculate an initial value of a membrane separation performance;
• an evaluation membrane separation performance determination unit configured to calculate the membrane separation performance for each of the measurement locations using the initial value of the membrane separation performance, and determine an evaluation membrane separation performance such that a difference between a calculated permeate quality calculated based on the membrane separation performance and the measured permeate quality falls within a predetermined range;
• a membrane separation performance comparison unit configured to compare the determined membrane separation performance with a reference membrane separation performance;
• and
• a separation membrane element state diagnosis unit configured to diagnose a state of the separation membrane element based on a predetermined state diagnosis reference of the separation membrane element from a result of the comparison of the membrane separation performance obtained by the membrane separation performance comparison unit.