Massachusetts Wastewater Practice Exam

What discharge rate should a 25,000 gallon waste storage tank release its wastewater to ensure a uniform discharge over a 12 hour period?

1. 10 gpm

2. 20 gpm

3. 35 gpm

4. 50 gpm

The correct answer is: 35 gpm

To determine the appropriate discharge rate for a 25,000-gallon wastewater storage tank over a 12-hour period, it is essential to calculate the rate required to evenly distribute the total volume over the given time frame. When you divide the total volume of wastewater (25,000 gallons) by the total time for discharge (12 hours), you convert hours to minutes for more straightforward calculations. Since 12 hours is equal to 720 minutes (12 hours x 60 minutes), the calculation to find the discharge rate in gallons per minute is as follows: 25,000 gallons ÷ 720 minutes = approximately 34.72 gallons per minute. Rounding this value, the closest and most practical discharge rate from the options provided is 35 gallons per minute. This ensures that the tank’s total volume is released uniformly throughout the 12-hour duration, maintaining a steady flow and avoiding any potential surges that could disrupt the treatment process or system performance. This approach to calculating discharge rates is critical in wastewater management to ensure effective treatment and compliance with environmental regulations.