Which pipe materials and structures offer better resistance to hydrogen sulphide (H₂S) corrosion in sewers carrying septic sewage?

Introduction / Context:
Hydrogen sulphide in septic sewage oxidizes to sulphuric acid on moist pipe crowns, causing severe crown corrosion. Material choice is crucial for durability.

Given Data / Assumptions:

• Presence of H₂S and associated sulphuric acid generation.
• Gravity sewers with air space and moist surfaces at the crown.

Concept / Approach:
Ceramic and vitrified (glazed) materials resist acid attack significantly better than unprotected concrete or steel. Glazed stoneware (vitrified clay) has a dense, acid-resistant surface ideal for H₂S environments.

Step-by-Step Solution:
Identify materials: concrete and steel are vulnerable without protective linings.Glazed ceramic surfaces exhibit excellent acid resistance.Select glazed stoneware as the best resistance among listed options.

Verification / Alternative check:
Many legacy sewers use vitrified clay precisely for corrosion resistance; modern systems may use PVC/HDPE or lined concrete for similar reasons.

Why Other Options Are Wrong:

• R.C.C. (unlined): Prone to acid attack; crown corrosion common.
• Asbestos cement: Better than plain concrete but inferior to vitrified ceramic.
• Glazed ware (generic ceramic): Overlaps with vitrified clay; the specific standard product is glazed stoneware pipe.
• Unlined mild steel: Highly susceptible to corrosion.

Common Pitfalls:
Ignoring need for linings/coatings or ventilation in long flat sewers with septicity.

Final Answer:
Glazed stoneware pipes