Environmental Engineering MCQ Questions & Answers | Civil Engineering

Understanding the Question:
This question is about water supply in a city. We know the average daily water use (1,00,000 m³). But, water demand isn't constant throughout the day. There's always a peak time when consumption is much higher.

Finding the Peak Demand:
The question asks for the maximum amount of water used during the highest demand hour of the day. This peak hourly demand is always higher than the average daily consumption because people tend to use more water during certain hours (like mornings and evenings).

Typical Peak Factors:
To calculate peak hourly demand, we use a peak factor. This factor tells us how much higher the peak hourly demand is compared to the average daily demand. This peak factor varies depending on factors like the city's size and water distribution system. Commonly, it falls within the range of 1.5 to 2.7.

Applying the Peak Factor:
Let's consider a peak factor of 1.5 (or 1.5 times the average daily demand). Then, the peak hourly demand would be 1,00,000 m³ * 1.5 = 1,50,000 m³.
If we used a peak factor of 2.7, the peak hourly demand would be 1,00,000 m³ * 2.7 = 2,70,000 m³.

Choosing the Right Answer:
Considering common peak factors, option B (1,50,000 m³) and option D (2,70,000 m³) are both plausible. The exact answer would depend on the specific peak factor used for that city. The question may require you to assume a typical peak factor or provide one in the problem itself.

A sewerage system needs to handle varying amounts of wastewater. It's not enough to design it for just one flow rate.

Maximum Flow: The system must be able to handle the peak flow, which occurs during times of high water usage (like after heavy rain or during certain times of the day). If the system isn't designed for maximum flow, it could overflow, causing pollution and other problems.

Minimum Flow: The system also needs to function properly during times of low flow. If the flow is too low, solids can settle in the pipes, leading to blockages and the production of unwanted gases. Minimum flow is important for maintaining a self-cleansing velocity.

Options A, B, and C are incorrect because they only consider one extreme of flow, which is not sufficient for a well-functioning sewerage system. A good design considers both extremes to ensure reliable and efficient operation.