ANS:E - 7 m

To calculate the width of a settling tank with a given detention period and flow rate, we can use the formula: Volume=Width×Length×DepthVolume=Width×Length×Depth Given:

• Detention period = 2 hours
• Flow rate = 378 cubic meters per hour

First, let's calculate the total volume of sewage that needs to be treated during the detention period: Volume=Flow rate×Detention periodVolume=Flow rate×Detention period Volume=378 m3/hour×2 hoursVolume=378m3/hour×2hours Volume=756 m3Volume=756m3 Now, we need to determine the width of the settling tank. Since we're not given the length or depth of the tank, we can't directly calculate the width. However, we can make assumptions about the dimensions of the tank to find a width that would accommodate the volume of sewage. Assuming a reasonable depth for a settling tank (typically ranging from 2 to 4 meters), we can calculate the required area (width × length) and then solve for the width. Let's take a depth of 3 meters as an example: Volume=Width×Length×DepthVolume=Width×Length×Depth 756 m3=Width×Length×3 m756m3=Width×Length×3m We're given that the detention period is 2 hours, so it's reasonable to assume a length that would allow for the flow to be treated over this period without a need for excessive depth. Let's assume a length of 6 meters: 756 m3=Width×6 m×3 m756m3=Width×6m×3m Now, we can solve for the width: Width=756 m36 m×3 mWidth=6m×3m756m3​ Width=756 m318 m2Width=18m2756m3​ Width≈42 m/hourWidth≈42m/hour Therefore, considering a length of 6 meters and a depth of 3 meters, the width of the settling tank would be approximately 42 m/hour42m/hour. Given the provided options, none of them matches the calculated value. It's possible that there might be a mistake in the data provided or the calculation.