In recent years, it becomes the problem that the water pollution in a close nature water area, or a river and the source area of tap water is big, especially industrial waste water and life waste water from miscellaneous sources become a factor. For this reason, advanced processing type waste-water-treatment technology increases for a time, and attracts attention as one of the eutrophication preventive measures. Then, while developing saved type phosphorus of energy and COD removal equipment adapting the electrochemical technique already put in practical use and aiming at reduction of power consumption, the performance can be maintained for a long period of time, and improvement in the technical reliability of the waste water treatment which maintenance-checks or is easy to maintain is aimed at.