Abstract: The present invention provides a method for treating a wastewater which enables one to treat a difficultly biodegradable wastewater, particularly an organic wastewater containing aminopolycarboxylic acids to substantially decrease COD at a low cost, in which the method for treating an organic wastewater containing aminopolycarboxylic acids, comprising subjecting the organic wastewater containing aminopolycarboxylic acids to a high-speed electrolytic oxidation treatment, particularly, a method for treating an organic wastewater which comprises conducting treatment with microorganism subsequent to the high-speed electrolytic oxidation treatment.

Abstract: The present invention provides a method for treating a wastewater which enables one to treat a difficultly biodegradable wastewater, particularly an organic wastewater containing aminopolycarboxylic acids to substantially decrease COD at a low cost, in which the method for treating an organic wastewater containing aminopolycarboxylic acids, comprising subjecting the organic wastewater containing aminopolycarboxylic acids to a high-speed electrolytic oxidation treatment, particularly, a method for treating an organic wastewater which comprises conducting treatment with microorganism subsequent to the high-speed electrolytic oxidation treatment.

Abstract: A hob which includes a cylindrical body having a longitudinal axis, a plurality of tooth elements each with a top edge portion of the same height arranged in succession along at least one helical line extending around the longitudinal axis of the hob wherein shoulder portions of leading or trailing sides of each of the tooth elements are reduced in their basic contour in staggered fashion, each of the tooth elements including a first shoulder edge portion intersecting the top edge portion at a distance located 0.05 m to 0.1 m from the center line of each of the tooth elements and a first angle of 25.degree. to 45.degree., a second shoulder edge portion disposed adjacent the first shoulder edge portion, and a third shoulder edge portion intersecting the second shoulder edge portion at a distance 0.5 m to 1.0 m from the top edge portion at a second angle of 3.5.degree. to 10.degree. wherein m represents a module.