A support device includes an acquirer configured to acquire data indicating water quality information of water to be treated, a pressure to supply the water to be treated to a membrane filtration device, a transmembrane pressure at a filtration membrane, a permeation flux at the filtration membrane, a frequency and cleaning conditions for cleaning the filtration membrane with cleaning water, and an outputter configured to output an optimum value of a current permeation flux, and a frequency and cleaning conditions for cleaning the membrane filtration device with the cleaning water in the future based on the data indicating the water quality information of the water to be treated, the pressure to supply the water to be treated to the membrane filtration device, and the transmembrane pressure at the filtration membrane, that have been acquired by the acquirer, by using a learned determination model acquired by performing learning processing using the data acquired by the acquirer.

A support device includes an acquirer configured to acquire data indicating water quality information of water to be treated, a pressure to supply the water to be treated to a membrane filtration device, a transmembrane pressure at a filtration membrane, a permeation flux at the filtration membrane, a frequency and cleaning conditions for cleaning the filtration membrane with cleaning water, and an outputter configured to output an optimum value of a current permeation flux, and a frequency and cleaning conditions for cleaning the membrane filtration device with the cleaning water in the future based on the data indicating the water quality information of the water to be treated, the pressure to supply the water to be treated to the membrane filtration device, and the transmembrane pressure at the filtration membrane, that have been acquired by the acquirer, by using a learned determination model acquired by performing learning processing using the data acquired by the acquirer.

A filtration membrane treatment device which performs ozone treatment on a filtration membrane, the filtration membrane treatment device including: a first supply portion which supplies an ozone-containing fluid to the filtration membrane; a measurement portion which measures a measurement value based on a pressure to the filtration membrane; and a control portion which adjusts, on the basis of a change in the measurement value measured by the measurement portion, a supply amount of the ozone-containing fluid to be supplied by the first supply portion.

A solution-type water treatment chemical, includes, as one, gluconic acid (salt) and a surfactant having an HLB determined by the following equation (1) satisfying the following equation (2), wherein in a relationship between concentrations of the gluconic acid (salt) and the surfactant and a molecular weight and HLB of the surfactant, the gluconic acid (salt) and the surfactant are contained such that the water treatment chemical does not form a gel or precipitate.
HLB=(Σinorganic value/Σorganic value)×10  (1)
Molecular weight>−34.4×HLB+1005  (2)

A solution-type water treatment chemical, includes, as one, gluconic acid (salt) and a surfactant having an HLB determined by the following equation (1) satisfying the following equation (2), wherein in a relationship between concentrations of the gluconic acid (salt) and the surfactant and a molecular weight and HLB of the surfactant, the gluconic acid (salt) and the surfactant are contained such that the water treatment chemical does not form a gel or precipitate.
HLB=(Σinorganic value/Σorganic value)×10  (1)
Molecular weight>−34.4×HLB+1005  (2)

Provided is a method for cleaning a filtration membrane provided in a membrane filtration device that is immersed in a liquid to be treated and performs solid-liquid separation on the liquid to be treated. When a transmembrane pressure difference exceeds a first predetermined pressure difference P1, a first cleaning step W1 for cleaning a filtration membrane is performed using a first chemical solution; when the transmembrane pressure difference immediately after performing the first cleaning step W1 exceeds a second predetermined pressure difference P2 that is lower than the first predetermined pressure difference, a second cleaning step W2 for cleaning the filtration membrane is performed using a second chemical solution having a concentration higher than the first chemical solution; and when the second cleaning step W2 is performed, the concentration of the second chemical solution and/or the cleaning time is changed according to the temperature of the liquid to be treated.

Provided is a method for cleaning a filtration membrane provided in a membrane filtration device that is immersed in a liquid to be treated and performs solid-liquid separation on the liquid to be treated. When a transmembrane pressure difference exceeds a first predetermined pressure difference P1, a first cleaning step W1 for cleaning a filtration membrane is performed using a first chemical solution; when the transmembrane pressure difference immediately after performing the first cleaning step W1 exceeds a second predetermined pressure difference P2 that is lower than the first predetermined pressure difference, a second cleaning step W2 for cleaning the filtration membrane is performed using a second chemical solution having a concentration higher than the first chemical solution; and when the second cleaning step W2 is performed, the concentration of the second chemical solution and/or the cleaning time is changed according to the temperature of the liquid to be treated.

A dosing control method for micro-flocculation in ultrafiltration, including: calculating a preset value of a first differential pressure before an initial backwash and a preset value of a second differential pressure before a final backwash in each chemically enhanced backwash cycle; calculating a preset value of a third differential pressure between the first differential pressure and the second differential pressure according to the preset value of the first differential pressure and the preset value of the second differential pressure; obtaining a predicted value of the third differential pressure according to a differential pressure curve plotted based on online filtration differential pressure data; and comparing the preset value of the third differential pressure and the predicted value of the third differential pressure to determine whether to dose. A dosing control system is also provided.

A dosing control method for micro-flocculation in ultrafiltration, including: calculating a preset value of a first differential pressure before an initial backwash and a preset value of a second differential pressure before a final backwash in each chemically enhanced backwash cycle; calculating a preset value of a third differential pressure between the first differential pressure and the second differential pressure according to the preset value of the first differential pressure and the preset value of the second differential pressure; obtaining a predicted value of the third differential pressure according to a differential pressure curve plotted based on online filtration differential pressure data; and comparing the preset value of the third differential pressure and the predicted value of the third differential pressure to determine whether to dose. A dosing control system is also provided.

A method for washing a filter is used in a seawater desalination process including a first filtration step for subjecting seawater to microfiltration or ultrafiltration, and a second filtration step for subjecting seawater after the first filtration step to a reverse osmosis treatment. The filter is a microfiltration membrane or ultrafiltration membrane used in the first filtration step. An iron compound is added to seawater in any stage in the washing method. The washing method includes a washing chemical liquid preparation step for preparing washing chemical liquid, and a sticking matter removal step for removing matter sticking to the filter by bringing the filter into contact with washing chemical liquid. In the washing chemical liquid preparation step, seawater after the first filtration step is mixed with at least hydrogen peroxide to prepare washing chemical liquid having an iron compound concentration of 1.50 mmol/L or more in terms of iron atoms.