To provide a water treatment method and apparatus which can efficiently separate water to be treated containing high concentration of nitrate nitrogen into residual nitrate nitrogen-containing water and ammonia nitrogen-containing water after applying a reduction process to the water to be treated, and can remove ammonia nitrogen from the ammonia nitrogen-containing water at a low cost without requiring addition of an alkali agent for pH adjustment.

The water treatment method comprises a reduction process for reducing nitrate nitrogen in the nitrate nitrogen-containing water to be treated to nitrogen gas and ammonia nitrogen by bringing the water to be treated into contact with hydrogen gas in presence of a reduction catalyst, a separation process for separating the water to be treated containing residual nitrate nitrogen and ammonia nitrogen after the reduction treatment by the reduction process into residual nitrate nitrogen-containing water and ammonia nitrogen-containing water by subjecting the water to be treated to electrolysis using a bipolar membrane, and an ammonia removing process for removing ammonia nitrogen from the ammonia nitrogen-containing water obtained by the separation method.