The methods of separating and recovering insoluble suspended pollutants (including oil film and oil beads) in wastewater by physical action can be divided into gravity separation, centrifugal separation and screen filtration interception.
The treatment units belonging to gravity separation method include sedimentation and air flotation (air flotation), and the corresponding treatment equipment includes grit chamber, sedimentation tank, oil separation tank, air flotation tank and its accessories. Centrifugal separation method itself is a kind of treatment unit, and the treatment devices used are centrifugal separator and water cyclone separator.
Screen filtration interception method has two processing units: mesh screen interception and filtration. The former uses grids and screens, while the latter uses sand filters and microporous filters.
The treatment method based on heat exchange principle also belongs to physical treatment method, and its treatment unit includes evaporation and crystallization. One way to remove organic matter from wastewater is activated carbon adsorption. Activated carbon treatment can be used together with activated sludge process, in which powdered activated carbon is used. Powdered activated carbon can adsorb substances toxic to microorganisms and finally collect them with sludge. The main danger of activated carbon method in sewage treatment is that invalid activated carbon may always exist in water.