The VertiCel® tanks in series design consists of an aerated-anoxic tank followed by an aerobic tank. 

The advantages of this design are:

• prevents short-circuiting of ammonia through the system
• reduces effluent levels to non-detectable
• achieves higher kinetic reaction rate so basin volume can be reduced
• can maintain different environments in each reactor for nitrogen phosphorus removal.
• The deep tank design reduces the footprint, thereby reducing construction and maintenance costs.