Crown corrosion of reinforced cement concrete sewer is caused by ______
- sulfur oxidizing bacteria
- iron oxidizing bacteria
- denitrifying bacteria
- fermentative bacteria
The Correct Option is A
Solution and Explanation
Step 1: Understand crown corrosion. Crown corrosion in reinforced cement concrete sewers occurs due to the conversion of hydrogen sulfide gas (\( H_2S \)) to sulfuric acid (\( H_2SO_4 \)). This reaction is facilitated by sulfur oxidizing bacteria like Thiobacillus.
Step 2: Role of sulfur oxidizing bacteria. In sewer systems, anaerobic bacteria produce \( H_2S \) in the wastewater. The \( H_2S \) gas rises to the crown (top) of the sewer and reacts with oxygen in the presence of sulfur oxidizing bacteria, producing \( H_2SO_4 \). The sulfuric acid corrodes the concrete at the crown of the sewer.
Step 3: Analyze the options. (1) Sulfur oxidizing bacteria: Correct, as they produce \( H_2SO_4 \), causing crown corrosion. (2) Iron oxidizing bacteria: Incorrect, as they primarily oxidize iron and are not involved in this process. (3) Denitrifying bacteria: Incorrect, as they convert nitrates to nitrogen gas, unrelated to corrosion. (4) Fermentative bacteria: Incorrect, as they are involved in anaerobic fermentation processes, not corrosion.
Top Questions on Design of Sewer
Sequentially arrange the steps involved in laying a sewer line:
A. Transferring the center line of the sewer to the bottom of the trench.
B. Setting sight rails over the trench.
C. Driving pegs to the level of the invert line of the sewer.
D. Placing the sewer in the trench.
Choose the most appropriate answer from the options given below:An activated sludge process (ASP) is designed for secondary treatment of 7500 m\(^3\)/day of municipal wastewater. After primary clarifier, the ultimate BOD of the influent, which enters into the ASP reactor, is 200 mg/L. Treated effluent after secondary clarifier is required to have an ultimate BOD of 20 mg/L. Mix liquor volatile suspended solids (MLVSS) concentration in the reactor and the underflow is maintained as 3000 mg/L and 12000 mg/L, respectively. The hydraulic retention time and mean cell residence time are 0.2 day and 10 days, respectively. A representative flow diagram of the ASP is shown below.
The underflow volume (in m}^3\text{/day, round off to one decimal place) of sludge wastage is \(\underline{\hspace{1cm}}\).
- GATE CE - 2021
- Environmental Engineering
- Design of Sewer
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Courage : Bravery :: Yearning :
Select the most appropriate option to complete the analogy.In the given figure, the numbers associated with the rectangle, triangle, and ellipse are 1, 2, and 3, respectively. Which one among the given options is the most appropriate combination of \( P \), \( Q \), and \( R \)?
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- GATE ES - 2025
- Hydrology