The advantages of installing motor-regulated overflow weirs at the sewage works of Modling show, reflecting the practical use of the electronic control of overflow weirs during 3 years, the necessity and effectivity of such a system. At this sewage plant electric control of the overflow weirs is combined with control of the immersion depth of the surface aerators in the aeration tanks. The motor-regulation implements two functions: equal flow to each of the three secondary settling tanks and optimal position of the surface aerators in the aerating tanks