A Biological Analysis of a Sequence Batch Reactor, Investigating the Use of Fixed-Film Media to Increase Treatment Efficiency

The Cromaglass® Corporation, based in Williamsport, PA, manufactures Sequence Batch Reactor (SBR) systems for domestic wastewater treatment. A Cromaglass® CA-60, capable of treating 6,000 gallons of wastewater per day, was installed in 2005 at Hepburn-Lycoming Elementary School, part of the Williamsport School District. This SBR was the subject of a study by the Lycoming College Clean Water Institute, in conjunction with Cromaglass®. The purpose of this study was to examine the effects of the insertion of fixed-film media into the mixed liquor chamber of the SBR. Fixed-film media provides a large surface area for the growth of bacteria and protozoans that aid in the treatment process. It was hypothesized that this media would lead to increased treatment efficiency through the cultivation of these biological treatment organisms. This study focused primarily on the biological analysis of the mixed liquor, examining changes in protozoan populations after the insertion of fixed-film media and the corresponding biofilm growth. It was determined that the populations of stalked ciliates, rotifers, and suctorians increased significantly after the insertion of the fixed-film media, which indicates a healthier treatment system. Stalked ciliates increased from approximately 3000/mL to over 16,000/mL. Rotifers increased from 266/mL to over 2600/mL. Finally, suctorians increased from 0/mL to almost 900/mL. INTRODUCTION Sewage treatment plants are the biggest source of point-source pollution entering our nation’s waterways (Chesapeake Bay Foundation, 2009). The nitrogen and phosphorus that remains in treated sewage effluent cause eutrophication, toxic algal blooms, dead zones, and other problems in the bodies of water into which they are released. Since the signing of the Chesapeake 2000 Agreement, emphasis has been placed on sewage treatment plants to upgrade their aging infrastructure and reduce the