Achieving Stringent Nitrogen and Phosphorus Removal

The Buxahatchee Wastewater Treatment Plant (WWTP) in Calera, Ala., was built in 1960. In 1985, it was upgraded to a 0.75-million-gal-per-day-capacity (mgd) extended aeration system with integrated clarifier and traveling aeration bridge, with a treatment objective of nitrification.

By 2004, the system could no longer handle the flow capacity brought on by community growth or the increasingly stringent nutrient limits set by the Alabama Department of Environmental Management. To resolve these issues an upgrade was in order, so the city of Calera decided to investigate several other treatment technologies. The plant required a written process performance guarantee from the manufacturer to ensure it would meet the new treatment requirements.

In March 2005, Buxahatchee installed a 2-basin AquaSBR sequencing batch reactor system and two 6-disk AquaDisk cloth media filters following the SBR system to further reduce TSS and phosphorus levels.

Buxahatchee chose technology from Aqua-Aerobic Systems, Inc. because it was the most cost-effective due to its small footprint requirements and ability to provide advanced nitrogen and phosphorus removal without the use of alum or other chemicals. Both the SBR and cloth media filter systems were designed to accomodate expected future community growth, so another upgrade will not be necessary for approximately 15 years.

Operation Results

The treatment scheme currently accomplishes low effluent TSS, NH3-N and Total P without the addition of chemicals. It is also designed for future Total Nitrogen limits, which are not yet required.

Doug Smedley, wastewater superintendent for the city of Calera, says, “Our continued outstanding pollution prevention scores can be attributed to the efficient operation of the AquaSBR system and AquaDisk filters.”

The Buxahatchee plant serves a portion of the city of Calera’s population and a few local industrial businesses.

Many engineers and water works managers travel to the WWTP to view the AquaSBR system and AquaDisk cloth media filters in operation for consideration in their retrofit and new construction projects.