Asahi Kasei Kabushiki Kaisha

Asahi Kasei Chemicals Corporation

Yutaka Gojo

Takahide Yoshida

Takahiro Konishi

Shinji Okubo

Kei Hattori

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.

Method for washing filter and method for desalinating seawater

This method, for regenerating a member used in a device that treats seawater, involves a cleaning step for removing deposits from the member. In the cleaning step, a first chemical solution containing an acid other than hydroxydicarboxylic acid and a second chemical solution containing hydrogen peroxide, a heavy metal compound and hydroxydicarboxylic acid are used.

Method of regenerating member and method of seawater desalination

A controller performs multiple regression analysis using an optimum chemical injection rate as a target variable and using one or more water quality indices of a raw water as explanatory variables and thereby derives a calculation formula for a basic chemical injection rate corresponding to the water quality indices. Next, the controller calculates the basic chemical injection rate corresponding to the water quality indices by substituting the measured values of the water quality indices of the raw water into the calculation formula. Then, the controller corrects the basic chemical injection rate based on a measured value of the water quality index of the treated water, thereby newly calculates a chemical injection rate, and outputs the newly calculated chemical injection rate as a control factor for a chemical injection pump while supplying the newly calculated chemical injection rate to calculation of the optimum chemical injection rate.

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Tokyo, Japan

Yutaka Gojo