Circular Sewer Properties Explained

Let's analyze the given statements about circular sewers to understand their characteristics in wastewater collection systems.

Sewer Deposits in Circular Sewers

Statement A says: "It offers less opportunities for deposits."

Circular sewers are known for their relatively good self-cleansing properties, especially when designed correctly with adequate slopes. The circular shape helps maintain a reasonable velocity across varying flow depths compared to other shapes like rectangular sections, particularly during low flow conditions (which occur for a significant portion of the day). A higher velocity, even at low flows, helps to keep suspended solids moving rather than allowing them to settle and form deposits.

Therefore, compared to some other common sewer shapes, circular sewers generally offer less opportunity for the accumulation of deposits, assuming proper design and flow conditions.

Statement A is true.

Sewer Economy and Material Use

Statement B says: "It is the most economical section since it utilizes a minimum quantity of material."

For a given cross-sectional area (which relates to the flow capacity of the sewer), a circular shape has the minimum possible perimeter. The cost of constructing a sewer is often significantly influenced by the amount of material used for the conduit wall (e.g., concrete, brickwork), which is directly related to the perimeter. Since the circular section requires the least perimeter for a given area, it requires the minimum quantity of construction material compared to other standard shapes like rectangular or egg-shaped sections for the same capacity.

This efficiency in material usage makes the circular section the most economical choice in many sewer construction projects.

Statement B is true.

Conclusion on Circular Sewer Statements

Based on the analysis, both Statement A regarding fewer deposits and Statement B regarding material economy are true for circular sewers under typical conditions and design practices.