The present invention consists of a method of pre-treatment of adulterated water for distillation, including adulterated water produced during hydraulic fracturing of shale rock during natural gas drilling. The bottom surface of the cover device extends in a plane. Since the marangoni dryer is adhered to the bath during drying, the wafers are not affected by laminar flow or exhaustion and water marks do not occur thereon. Portions of the electromigration-inhibitingelectrically conductive material are removed to form the plugs with surfaces co-planar a surface surrounding the plugs. When it is determined that no dot should be formed, a process is performed to diffuse a gradation error for the entire target block to the unconverted pixels in another block and convert image data for pixels in the target block.