Dissolved Air Flotation

Inhaltsverzeichnis

1. Frontmatter

2. Chapter 1. Fundamentals of Dissolved Air Flotation

   Roumen Kaltchev

   Abstract

   Dissolved air flotation is a process that aims to separate a solid phase from a liquid phase. In the field of water treatment, the preferred term is “clarification”, probably because it has a “purifying” and “clean” connotation that corresponds well to the final effect sought by its implementation.

3. Chapter 2. The Main Equipment of a Dissolved Air Flotation Plant

   Roumen Kaltchev

   Abstract

   The specific features of dissolved air flotation make this clarification technology almost always used in combination with chemical treatment. The few exceptions are mainly biological sludge thickening and some applications in food processing such as the removal of particulate grease (non-emulsified). The reason for this is mainly that this technology can clarify very quickly and very well if it is used under the best conditions. Well, a chemical treatment by flocculation or by coagulation + flocculation ensures the most favourable conditions from several points of view. It is also true that chemical treatment is beneficial and even indispensable in a large number of cases of clarification by sedimentation, as it improves the efficiency of separating polluting materials. In sedimentation, it certainly makes it possible to significantly increase the sedimentation velocity, but in flotation its importance can be even more significant, because it favours not only the trapping and agglomeration of micro-flocs and the quality of liquid/solid separation, but also the quality of the adhesion of micro air bubbles to the flocs.

4. Chapter 3. Circular DAF Clarifiers

   Roumen Kaltchev

   Abstract

   Circular DAF clarifiers have the advantage that they are usually cheaper to build than rectangular DAF clarifiers. Of course, this comparison is valid for the same surface area and comparable hydraulic concepts.

5. Chapter 4. Rectangular DAF Clarifiers with Non-assisted Clarification

   Roumen Kaltchev

   Abstract

   These are the simplest and most basic DAF clarifiers and probably constitute the largest number of installations each year.

6. Chapter 5. Rectangular DAF Clarifiers with Assisted Clarification

   Roumen Kaltchev

   Abstract

   As previously mentioned, the hydraulic concept of simple rectangular DAF clarifiers rarely allows hydraulic loads above 8 m/h, in some cases up to 10–12 m/h.

7. Chapter 6. High Hydraulic Loading Rectangular Clarifiers with Non-assisted Clarification

   Roumen Kaltchev

   Abstract

   Although there are many forms and designs of different types of rectangular DAF clarifiers, the focus of this chapter will be on large ones, operating at high hydraulic loading (20–40 m/h), which are used for the clarification of natural waters and seawater for drinking water production. These clarifiers have certain design and operational features that differentiate them from the simple rectangular non-assisted clarification DAF clarifiers described in Chap. 5.

8. Chapter 7. DAF Clarifiers with Built-in Sand Filter

   Roumen Kaltchev

   Abstract

   There are many ‘clean’ or ‘relatively clean’ water treatment applications where the treatment process involves clarification followed by sand filtration. These can be drinking water applications, process water for industrial use or tertiary wastewater treatment. If the clarification stage is done by dissolved air flotation, then it is easy to imagine that the idea of combining the DAF clarifier with a gravity sand filter has soon occurred to many engineers.

9. Chapter 8. The Main Applications of Dissolved Air Flotation

   Roumen Kaltchev

   The few domains of application discussed in this chapter are the best known, the most “traditional” and the most frequent. But they are far from covering all the cases in which dissolved air flotation can be used successfully. In fact, it is applicable in almost all cases of clarification, provided that the suspended solids to be separated meet some basic conditions:

10. Chapter 9. Conclusions

    Roumen Kaltchev

    Abstract

    What are the conclusions to be drawn from the previous chapters and the important points to which particular attention should be paid when analysing the feasibility, selection and sizing of equipment and the implementation of a dissolved air flotation plant? What are the main criteria and parameters to be considered first? What are the possible ways of optimising the operation of a plant? The following few pages attempt to offer some advice on these subjects.

11. Backmatter