Resistance to sulfide corrosion in sewers: Among the following materials, which sewer type best resists hydrogen sulfide–induced corrosion in domestic wastewater environments?

Introduction / Context:
Hydrogen sulfide produced under septic conditions in sewers can oxidize to sulfuric acid at moist surfaces, severely corroding many traditional materials. Material selection is therefore crucial to ensure durability and low lifecycle cost in corrosive wastewater atmospheres.

Given Data / Assumptions:

• Environment: domestic sewage with potential for sulfide generation.
• Materials considered: brick, cast iron, reinforced concrete, and lead.
• Evaluation based on chemical resistance to sulfide attack and acidic conditions.

Concept / Approach:
Acidic condensates attack cement paste in concrete and mortar in brickwork, and also corrode unprotected ferrous metals. Traditionally, vitrified clay, certain plastics, and lead have shown strong chemical resistance to such attack. Among the options, lead exhibits excellent corrosion resistance to sulfuric environments compared with brick, cast iron, and ordinary R.C.C.

Step-by-Step Solution:
Assess brick sewer: mortar and bricks are vulnerable to acid dissolution.Assess cast iron: unlined iron suffers from acid corrosion unless protected.Assess R.C.C.: sulfate/sulfuric acid degrade cementitious matrix and steel unless specially protected.Lead: notable chemical resistance in acidic wastewater settings; thus most resistant among given choices.

Verification / Alternative check:
Historically, vitrified clay and lead have been used where high corrosion potential exists. Modern alternatives include PVC, HDPE, and glass-fiber reinforced pipes with appropriate linings. Within the listed legacy materials, lead is the most corrosion resistant.

Why Other Options Are Wrong:
Brick: mortar joints and bricks deteriorate under sulfuric acid attack.Cast iron: corrodes without protective linings or coatings.R.C.C.: cement paste is chemically vulnerable; requires liners or coatings to resist.

Common Pitfalls:

• Assuming concrete is universally durable in all wastewater conditions without liners.
• Overlooking microbially induced corrosion at the air–sewage interface.

Final Answer:
Lead sewer