Typical ( f_D ) = 0.2 to 0.5.
The German standard ATV-DVWK-A 131 (now superseded by DWA-A 131) provides with secondary clarification, nitrification, and denitrification. It applies to municipal wastewater treatment plants serving >1,000 population equivalents (PE). The standard emphasizes: atv dvwk a 131 epdf top
Perhaps the most technical feature of the standard is the adoption of the Muskingum-Cunge method for flow routing. This mathematical model calculates how a flood wave changes shape as it moves through a pipe network. This is crucial for preventing "water hammer" effects and ensuring that peak flows from different sub-catchments do not synchronize at a junction point, which is a common cause of urban flash flooding. Typical ( f_D ) = 0