The basic concepts of treating humic waters with dissolved air flotati
on are discussed emphasizing the important role of zeta potential in t
he forming of floc-air-bubble-agglomerates. Then practical experiences
from Finnish drinking water treatment plants are presented. When surf
ace water is used as a raw water, it is more or less humic. Thirty-six
such plants have dissolved air flotation as a clarification process,
the oldest one dating from 1965. They serve about one million people.
All of them are working well proving that dissolved air flotation is a
suitable method in humic water treatment. Some special cases are disc
ussed in detail. These are cases where sufficient data about design, o
peration and costs are available and which it is hoped can help other
designers. The last plant referred to is an example of an advanced tre
atment process where dissolved air flotation is an integrated unit pro
cess.