Use of dissolved air flotation in potable water treatment in Finland

Abstract

The basic concepts of treating humic waters with dissolved air flotation are discussed emphasizing the important role of zeta potential in the forming of floc-air-bubble-agglomerates. Then practical experiences from Finnish drinking water treatment plants are presented. When surface 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 discussed in detail. These are cases where sufficient data about design, operation and costs are available and which it is hoped can help other designers. The last plant referred to is an example of an advanced treatment process where dissolved air flotation is an integrated unit process.

Mathematical Model of the Coagulation/Dissolved Air Flotation (DAF) Process Based on the Conservation of Momentum

“…Później proces DAF był stosowany w oczyszczaniu ścieków i uzdatnianiu wody. Szczególne zalety tego procesu stwierdzono w oczyszczaniu wód powierzchniowych o niskiej mętności zanieczyszczonej organizmami fitoplanktonowymi lub substancjami humusowymi, zwłaszcza w okresach niskiej temperatury, kiedy obserwuje się niską skuteczność procesu sedymentacji [1][2][3]. Pierwsze aplikacje metody DAF do oczyszczania wód powierzchniowych miały miejsce w Skandynawii w latach 60. ubiegłego wieku.…”

“…W celu sprawdzenia wykonalności proponowanych metod przeprowadzono badania laboratoryjne. Wodę do badań przygotowano z wody wodociągowej zanieczyszczonej ekstraktem kwasów humusowych w dawce 13,6 cm 3 /dm 3 Po przeprowadzeniu oczyszczania wody dokonano oceny jej jakości z wykorzystaniem spektrofotometru Hitachi U-2001 w celu oznaczania barwy wody i mętnościomierza Hach 2100N do oznaczania mętności wody.…”

Study on the Influence of the Sizes of Microbubble on Water Treatment

“…Japanese, in equipment and technology, had more extensive research and accessed a number of patents. Finlander used air flotation to clean water, from 1965 to 1992, 36 water treatment factories for drinking water were established, the total daily water purification capacity was 263,552m 3 and could supply for about one million people that was 20% of total population of Finland [4]. Swedish, as Finlander, had more than 100 large and small air flotation water treatment factories.…”

“…In China the use of air flotation technology started late, in the late of 1960s, dissolved air flotation devices were used in the salt making industry and oil wastewater treatment, due to technical problems, they were unrewarding [4]. In the design and test process of the wastewater treatment plant of Suzhou Cotton Textile Factory in 1975, the researchers found that the light weight particles in the printing and dyeing wastewater could be quickly gathered.…”

In situ Remediation Technologies Associated with Sanitation Improvement: An Opportunity for Water Quality Recovering in Developing Countries

“…The technology was then adapted to treat water and wastewater through dissolved air flotation (e.g. Heinänen et al, 1995). Ultrafiltration membranes in turn have been mainly used for drinking water production (2 million m 3 /day worldwide according to Laîné et al, 2000).…”