ABSTRACT
In the context of this book on sewer processes, it is important to understand that a sewer consists of five main parts, also referred to as phases:
1. A water phase including suspended particles 2. Biofilms attached to the submerged solid parts of the sewer 3. Sewer sediments also referred to as deposits 4. A sewer atmosphere or headspace 5. Sewer walls exposed to the sewer atmosphere including a moisture layer
and adhered substances
The chemical and biological processes proceed within these phases, at their internal surfaces such as particle surfaces of the suspended water phase and at the sewer walls. Furthermore, mass transfer, i.e., exchange of substances, takes place between the different phases, e.g., transfer of volatile substances from the water phase into the sewer atmosphere.
