Biotower Trickling Filters Return to Process Page

What is Advanced Secondary treatment and why is it done?    Advanced Secondary treatment begins at the end the secondary settling stage.  The wastewater at this point is quite clean compared to the state that it arrived in at the Treatment Facility.  One of the last remaining concerns is the amount of ammonia in the wastewater.  Ammonia at higher levels is toxic to aquatic life and can result in harm to the environment.  To remove the ammonia from the wastewater, La Porte's Treatment Facility involves a special type of Trickling Filter called a biotower.  The biotowers function similar to a regular tricking filter, except that a biotower has twenty feet of media and a regular trickling filter has about five feet.  Just like a regular trickling filter, a biotower has a moving distribution system on the top of the tower that sprays the wastewater on the top of a plastic media.  The water then trickles down this media past bacteria that are growing on it.  In the case of the biotowers, a specialized bacteria called a "nitrifier" converts the ammonia in the water to nitrate, which is an organic nutrient source for plants.  As the nitrifiers age and die, they are "sloughed" off by the passing water and collected during the Advanced Secondary settling stage of treatment.