To provide a treatment method and equipment for controlling the charged amount of organic waste, for example, in an anaerobic treatment being required conditions in biological treatment to be within a proper range.

In the method for biologically treating liquid organic waste or sewage, the potential of the liquid organic waste or the sewage is measured with an electrode composed of a reference electrode and an ion electrode and the measured potential is used for the control of treatment conditions required for the biological treatment. Therein, the biological treatment is an anaerobic treatment of the liquid organic waste and the measured potential is used for the control of the load of the organic waste or the treatment is a denitrifying treatment of the sewage and the measured potential is used for the filling control of the amount of addition of a hydrogen donor to denitrifying treatment. Otherwise, the treatment is a dephosphorization of the sewage and the measured potential is used for the control of the filling amount of air quantity to the anaerobic process and the quantity of return sludge.