The degasser can have a degassing membrane that can be constructed from non-porous silica. The degassing membrane can be highly permeable to carbon dioxide but less permeable oxygen or nitrogen gases. Pressure in the dialysate and the degasser can be controlled in order to control the amount of carbon dioxide and other gases in dialysate leaving the degasser. The degassing membrane may be placed in a degassing module in a dialysate flow path to remove dissolved carbon dioxide from the dialysate.