For decades, conventional multi-stage biological nutrient removal (BNR) system has been the standard process utilized by wastewater treatment plants to reduce total nitrogen (TN) and total phosphorus (TP) in wastewater. These systems are effective but have high energy costs and require a large number of tanks to handle the wastewater during each of the various stages in the process.
A phase-activated sludge system (PASS) reduces energy consumption and requires fewer tanks. It can be retrofitted into an existing plant as part of a plant upgrade to nutrient removal or designed as a greenfield installation.
A PASS saves energy by combining the aerobic and anoxic tanks. Diffusers alternate between the on and off position based on a preprogrammed schedule, which shifts the tank from aerobic to anoxic conditions and eliminates the need for internal recycles. This and other features help reduce energy, mitigate carbon management, and results in improved nutrient removal at lower cost.