The most efficient cross section of sewers in a separate sewerage system is circular. This is because a circular cross section has the least surface area for a given volume, which minimizes friction losses. Additionally, a circular cross section is the strongest and most stable shape, which minimizes the risk of collapse.
A parabolic cross section is not as efficient as a circular cross section because it has a larger surface area for a given volume. This results in greater friction losses and a higher risk of collapse.
A rectangular cross section is also not as efficient as a circular cross section because it has a larger surface area for a given volume. Additionally, a rectangular cross section is not as strong as a circular cross section, which increases the risk of collapse.
A new egged cross section is not a common type of sewer cross section. It is not as efficient as a circular cross section because it has a larger surface area for a given volume. Additionally, a new egged cross section is not as strong as a circular cross section, which increases the risk of collapse.