Assertion (A): A 0.3 m freeboard is maintained above the wastewater surface inside septic tanks. Reason (R): This space provides adequate room for scum accumulation_________________?
Show answer Hide answer
Answer: A. Both A and R is true and R is the correct explanation of A
Explanation
The 0.3 m freeboard provides essential empty space above the wastewater surface for scum accumulation inside tanks. This designated vertical clearance also accommodates the safe release and venting of generated sewer gases. Both the assertion and the reason are true, and the reason accurately explains the purpose of the freeboard. Septic tanks function as primary sedimentation and anaerobic digestion units for domestic wastewater treatment systems. Anaerobic breakdown of organic solids produces gases such as methane and hydrogen sulfide that require venting space. Scum layers float on the liquid surface and expand over time, necessitating dedicated storage volume above the waterline.
Option B is incorrect because the stated reason directly explains why the freeboard dimension is necessary. Option C is incorrect because the provided reason is completely accurate and supports the assertion. Option D is incorrect because the initial assertion about maintaining a 0.3 m freeboard is entirely true.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. Assertion (A): Lead-white based paints are discouraged for structural steelwork. Reason (R): White lead paints fail to prevent metal oxidation. Choose the appropriate option below?
Show answer Hide answer
Answer: A. Both A and R are true and, R is the correct explanation of A
Lead-based paints undergo chemical reactions with steel surfaces that lead to premature paint film failure. These paints fail to provide adequate corrosion protection because they react adversely with metallic iron subst...
Q2. Quality building stone should possess a minimum crushing strength exceeding____________?
Show answer Hide answer
Answer: B. 100 MPa
Quality building stone suitable for durable construction must possess a minimum crushing strength exceeding 100 MPa. Laboratory compression testing ensures that selected natural rocks can safely support heavy superstruct...
Q3. An excess of alumina in brick clay causes the fired brick to______________?
Show answer Hide answer
Answer: D. to crack and warp on drying
Excessive alumina in brick clay increases plasticity and causes severe shrinkage during the drying phase. This high shrinkage rate generates internal mechanical stresses that result in cracking and warping of bricks. The...
Q4. Applying a surface glaze transforms porous earthenware into______________?
Show answer Hide answer
Answer: D. impervious
Applying a vitrified surface glaze melts and seals the open pores characteristic of raw earthenware. This glazing process transforms the permeable clay body into a completely impervious and waterproof finished material....
Q5. Granite is generally unsuitable for routine masonry construction because_______________?
Show answer Hide answer
Answer: C. it is costly
Granite is generally expensive to quarry, cut, and polish, which limits its use in routine masonry construction. The extreme hardness of granite requires specialized diamond cutting tools and intensive labor effort to sh...
Q6. For testing cement compressive and tensile strength, mortar specimens are prepared using a cement-to-standard-sand ratio of___________________?
Show answer Hide answer
Answer: B. 1:3
Standard mortar specimens for cement testing are mixed using a strict cement-to-standard-sand ratio of 1:3. This precise ratio ensures uniform test results across different laboratories evaluating cement compressive and...