Switzerland operates 24 ozone plants per 1 million inhabitants which brings it to first place in the world. A comparison between two Swiss waterworks, one with low frequency (Moos Waterworks) and one with increased frequency (Lengg Waterworks) shows the following operating costs: A total of 1.41 cents/m³ for the Lengg Waterworks, and 1.88 cents for the Moos Waterworks including capital, maintenance, and miscellaneous expenses, at a dosage of 1.5 g ozone/m³. To reduce the phenol compounds and the haloforms, it is advantageous to add a higher ozone concentration. This is also the case for removing color and UV extinction due to the dissolved organics. A higher dosage than normal will, however, have a negative effect on the flocculation and on the bacterial regrowth if ozonation is not followed by granular activated carbon (GAC) treatment. During a plant breakdown, however, the availability of increased ozone dosage above normal levels is important to operate the partially disabled plant.