Si removal from aqueous streams of minerals processing plants

A method for removing soluble and/or colloidal Si-compounds from an aqueous stream (100, 200a, 300a, 400b) of a minerals processing plant is provided. The method comprises: adding coagulant(s) and/or flocculant(s) and/or flotation chemical(s) to the aqueous stream (100, 200a, 300a, 400b) in order to facilitate formation of flocs comprising at least some of the Si- compounds, and in order to form a treated aqueous stream (101, 201, 301, 401), subjecting the treated aqueous stream (101, 201, 301, 401) to cleaning flotation in order to separate at least some of the Si-compounds as a cleaning flotation overflow (103, 203, 303, 403), and removing the cleaning flotation overflow (103, 203, 303, 403). The cleaning flotation comprises gas bubbles, at least 90 % of the gas bubbles having a diameter of from 0,2 to 250 µm.