The invention provides a method for removing
silicon from waste water discharged from a
coal water
slurry gasification process. The
silicon removal method comprises the following steps: step S1, adjusting the pH value of the
effluent to 10-13, and flocculating the
effluent with a flocculant to obtain a first-stage
mixed waste water; step S2, performing coagulation treatment on that first-stage
mixed waste water by using a coagulant aid to obtain the second-stage
mixed waste water; step S3, carrying out
sedimentation treatment on that second-stage mixed waste water to obtain secondary supernatant and secondary precipitated
sludge, and returning at least part of the secondary precipitated
sludge to the second-stage mixed waste water for auxiliary coagulation treatment in the step S2. The invention adjusts the pH value of the
effluent to 10-13 before the
flocculation treatment to facilitate the formation of
alum flower between the dissolved
silicon and the flocculant, thereby improving the
flocculation efficiency of the dissolved silicon; at that same time, the secondary precipitate
sludge obtained by circumfluence
sedimentation in the step S2 is used as a contact medium to acceleratethe growth of the precipitate, improve the coagulation effect and improve the silicon removal effect.