Step 1: Understanding the Concept:
Wastewater treatment in food processing facilities often utilizes biological systems to reduce organic load (Biological Oxygen Demand, BOD) before disposal.
These systems can be aerobic, anaerobic, or symbiotic.
Detailed Explanation:
An oxidation pond (also known as a stabilization pond or lagoon) is a shallow, large-surface-area basin designed to treat wastewater through the symbiotic interaction of sunlight, algae, and bacteria.
The biological mechanism operates as follows:
1. Algae in the shallow pond utilize sunlight and carbon dioxide ($\text{CO}_2$) to perform photosynthesis, which releases dissolved oxygen into the water.
2. Aerobic bacteria use this dissolved oxygen to metabolize and break down organic pollutants in the wastewater.
3. This bacterial decomposition releases $\text{CO}_2$, ammonia, and nitrates, which serve as nutrients for further algal growth.
This natural, low-cost system effectively reduces organic waste in the water.
- Anaerobic ponds (B) are deep, operate without oxygen, and do not rely on sunlight or algae.
- Activated sludge (C) is an engineered, intensive aeration process, not a shallow pond system.
Step 2: Final Answer:
The biological treatment system described is called an Oxidation pond.