Wastewater Lagoons: Alabama Grade I Operator Guide
Under ADEM Admin. Code 335-10-1-.03, Grade I is defined specifically as a wastewater treatment lagoon, of any size — the only Alabama wastewater grade tied to a single process type rather than a flow range. Lagoons are common at small towns and rural systems across Alabama because they are low-cost to build and operate compared to mechanical plants, though they require more land.
How a lagoon treats wastewater
A lagoon is an engineered pond where treatment happens through natural and photosynthetic (algal) self-purification processes, with or without supplemental aeration, over a long detention time (often 30-180+ days, far longer than a mechanical plant's hours-to-a-day). Alabama's definitions recognize several lagoon types: non-aerated (relying entirely on natural bacterial/algal action and oxygen from wind mixing and photos