What type of lagoon has both aerobic and anaerobic conditions?

Facultative lagoons are designed to support both aerobic and anaerobic processes within the same system. In these lagoons, the upper layer is typically aerobic due to oxygen supplied by wind action and photosynthesis from algae, while the deeper layers become anaerobic as oxygen is depleted. This dual environment allows for diverse microbial activity, promoting the breakdown of organic matter by both aerobic and anaerobic bacteria.

This type of lagoon can effectively handle varying organic loads and provides a balance that optimizes the treatment process. The aerobic conditions in the upper layer help stabilize the waste, while the anaerobic processes in the lower layer further reduce the organic material and contribute to the overall efficiency of the lagoon. This versatility makes facultative lagoons an essential component in wastewater treatment systems, capable of adapting to varying influent conditions.