Which type of wastewater treatment involves both aerobic and anaerobic processes?

Facultative lagoons are designed to utilize both aerobic and anaerobic processes for the treatment of wastewater. In these lagoons, the upper layer is aerobic due to the presence of oxygen from the atmosphere, which promotes the breakdown of organic matter by aerobic bacteria. Beneath this aerobic layer, a deeper anaerobic layer exists where the absence of oxygen allows anaerobic bacteria to further decompose organic materials.

This dual-process approach effectively treats wastewater by allowing different microbial communities to thrive in their respective environments, helping to stabilize the organic load and reduce pollutants in the water. The combination of aerobic and anaerobic treatment not only enhances the removal of solids and organic matter but also improves the quality of the effluent.

Other treatment methods, such as activated sludge and trickling filters, primarily focus on aerobic processes, relying on oxygen to decompose organic matter. Composting, while involving microbial activity similar to anaerobic digestion, mainly emphasizes aerobic decomposition in a managed environment. Therefore, facultative lagoons stand out with their ability to operate in both aerobic and anaerobic conditions, making them unique in their treatment capability.