Tennessee Wastewater Operator Practice Exam

What five day BOD to nitrogen to phosphorus ratio should be maintained in attached growth nitrification processes?

1. 80:4:1

2. 100:5:1

3. 120:6:1

4. 150:9:1

The correct answer is: 100:5:1

In attached growth nitrification processes, maintaining an appropriate ratio of five-day Biochemical Oxygen Demand (BOD) to nitrogen to phosphorus is crucial for effective biological treatment and nutrient removal. The selected ratio of 100:5:1 indicates a balanced approach that provides sufficient organic matter (BOD) supporting microbial growth while ensuring adequate nitrogen and phosphorus levels for the nitrifying bacteria. A 100:5:1 ratio reflects the general guidelines in wastewater treatment practices that facilitate optimal growth conditions for the nitrifying microorganisms. Specifically, this ratio ensures that there is enough nitrogen to stimulate the growth of nitrifying bacteria, which rely on this nutrient to convert ammonia into nitrite and then to nitrate, while the phosphorus component supports overall cellular metabolism and function. The alternatives with different ratios may not provide the same level of efficiency or could lead to imbalances. For instance, a significantly higher ratio could imply an excess of BOD or nitrogen that could adversely affect the nitrification process by potentially leading to competition among organisms for nutrients or oxygen, while a lower ratio could limit microbial growth or slow down the nitrification process due to insufficient nutrients. Therefore, maintaining the 100:5:1 ratio is ideal for optimizing the biological treatment efficiency, allowing for effective removal of nitrogen