The present invention is to provide a water treatment device and a water treatment method that can efficiently remove soluble silica in water to be treated. A water treatment device 1 of the present invention comprises: a soluble silica deposition section 13 that deposits soluble silica dissolved in water to be treated W1, the water to be treated W1 having a concentration of aluminate ion represented by general formula (1) below and a pH that are in predetermined ranges; and a solid-liquid separating section 14 that separates the deposited soluble silica from the water to be treated W1 to obtain treated water W2 formed by removing the soluble silica from the water to be treated W1.
€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ[Al(OH) 4 ] - ... Formula€ƒ€ƒ€ƒ€ƒ€ƒ(1)
