Man-made lagoons have been used worldwide for the treatment of domestic and industrial wastewater, it seems, forever. All waste lagoons were first designed and thoughtfully planned considering their locations, soil makeup, and waste reduction processes prior to being implemented. The biological process of organic waste reduction is always a consideration of waste lagoon designs. There are three biological concepts considered for waste lagoons -
- Anaerobic lagoons, commonly at least 10 feet deep, have no dissolved oxygen in the lagoon water. Acid and methane bacteria work together to convert complex organics eventually to gases. There is very little, if any, mixing in these lagoons, and they are often used as an initial difestion process with aerobic lagoons downstream.
- Facultative lagoons are more shallow and were conceived to allow for anaerobic digestion in the bottom sediments and to allow for aerobic bacteria to consume the liquid and gaseous intermediate organic products in the water column. Surface water movement supplies the only water movement and daytime algae are the oxygen source for the aerobic bacteria.
- Aerated lagoons are deeper, often up to 20 feet in depth, but mechanical and diffused air systems continuously provide dissolved oxygen to aerobic in the sediments and water column. The aerators are also the source of mixing in the lagoon.