Soil of waste water contains nearly 60% of organic compounds. Biologic steps of waste water treatment care for there destruction by aerob microbes. The oxygen consumption is a measure for the biologic loading of the water. Surfactants increase this biochemical oxygen demand (BOD) significant; once, they need the oxygen themself, twice, other organic compounds can be solubiliced in the surfactant solution. The BOD maximum of flooder water is given by law. Thats why the working parameters like reflux quotient must be adjusted to working temperature and water composition.