Septic Pumper Practice Test 2025 - Free Septic System Pumper Practice Questions and Study Guide

The highest concentration of algae growth in a facultative lagoon is typically found near the top. This is because algae require sunlight for photosynthesis, which is essential for their growth. The top layer of the lagoon receives the most sunlight, allowing for optimal photosynthetic conditions.

In facultative lagoons, the upper layer is usually aerobic due to the contact with the atmosphere, which supports various biological processes, including those carried out by algae. These organisms thrive in well-lit and oxygen-rich environments, leading to significant growth at the surface.

In contrast, the lower layers, such as middepth and the bottom, experience less light and oxygen availability, which do not favor algae proliferation. Additionally, the sludge layer, composed of decomposed organic matter and anaerobic conditions, is not conducive to algae growth, as these conditions are primarily suited for bacteria that break down the organic material.

Thus, for optimal algal growth, the surface of the lagoon is the ideal location due to its exposure to sunlight and oxygen, confirming why the highest concentration occurs there.