Final answer:
Increasing the recirculation rate in a trickling filter contributes to the reduction of influent BOD in wastewater treatment by increasing oxygen concentration, promoting bacterial activity, and enhancing nutrient removal.
Step-by-step explanation:
Increasing the recirculation rate in a trickling filter can contribute to the reduction of influent BOD in wastewater treatment through several mechanisms:
- Increased O2 concentration: By increasing the recirculation rate, more oxygen is introduced into the wastewater, which provides an optimal environment for aerobic bacteria to decompose the organic matter. This leads to the breakdown of biological oxygen demand (BOD) and the reduction of organic pollutants.
- Increased bacterial activity: The higher recirculation rate promotes the growth and activity of bacteria that decompose dead organic matter. These bacteria consume organic compounds and convert them into harmless byproducts such as carbon dioxide and water.
- Enhanced nutrient removal: A higher recirculation rate can help lower the nutrient levels in the wastewater. Nutrients like nitrogen and phosphorus contribute to the growth of algae and other aquatic plants, which can increase BOD levels. By increasing the recirculation rate, the trickling filter can efficiently remove these nutrients, preventing excessive plant growth and reducing BOD levels.