For non-scouring velocity 5 m/sec, the type of sewers generally preferred to, is

ANS:C - glazed bricks sewers

Glazed brick sewers are a type of sewer system constructed using bricks that have been coated with a glaze. The glaze is a vitreous material applied to the surface of the bricks and then fired at high temperatures to create a smooth, impermeable, and glass-like finish. This glazing process provides several benefits and characteristics to the sewer system:

1. Waterproofing: The glaze creates a waterproof barrier on the surface of the bricks, preventing the intrusion of groundwater into the sewer system and minimizing the risk of leakage.
2. Corrosion Resistance: Glazed bricks are highly resistant to corrosion caused by chemical reactions with sewage and wastewater. The impermeable glaze protects the underlying brick material from degradation, extending the lifespan of the sewer system.
3. Smooth Surface: The glazed surface of the bricks provides a smooth interior lining for the sewer pipes. This smoothness promotes the efficient flow of sewage and reduces the likelihood of sedimentation and clogging within the sewer system.
4. Abrasion Resistance: The glazed surface is resistant to abrasion, minimizing wear and tear on the sewer pipes caused by the movement of solids and debris within the wastewater.
5. Ease of Cleaning: The smooth and non-porous nature of the glazed surface makes it easier to clean and maintain the sewer system. Regular cleaning helps prevent the buildup of deposits and ensures the continued performance of the sewer pipes.

Glazed brick sewers have been used historically in some sewer systems, particularly in older infrastructure. However, they are less commonly used today compared to other materials such as concrete, PVC, and ductile iron due to certain limitations and challenges. These may include higher costs of materials and installation, potential for cracking or chipping of the glaze over time, and limited availability of skilled labor for construction and maintenance. Overall, while glazed brick sewers offer advantages in terms of durability, corrosion resistance, and smoothness of the interior surface, they may not be as widely used in modern sewer systems as other materials that offer similar or enhanced properties at a lower cost.