The VertiCel® process is a series of VLR® contact tanks followed by fine-bubble diffuser reactor tanks. This suspended growth activated sludge process is designed to minimize energy consumption and accomplish Biological Nutrient Removal (BNR). The process uses two types of aeration devices to optimize aeration efficiency. Power costs of the VertiCel process are 20 to 30% lower than competitors. It uses deep rectangular reactors for reduced space requirements and can be retrofitted into existing rectangular aeration basins.