Abstract
The behavior of biological particles in DAF (dissolved air flotation) process was analyzed by employing PBT (Population balance theory). After decline growth phase of activated sludge, the value of the initial collision-attachment efficiency was increased over than 0.35 corresponding relatively high value in the whole life cycle of microorganism. For practical application of DAF as a solid separation process. It is desirable that microbial particles should be operated to perform high solid removal efficiency in biological wastewater treatment.