Nitrification performance and potential at the Ames Water Pollution Control Facility

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Evans, Eric
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Civil, Construction, and Environmental Engineering

The Ames Water Pollution Control Facility (AWPCF) treats wastewater generated by Ames' residents and industries. The current facility was designed by RCM Associates of Minneapolis, Minnesota. Dr. Harvey Gullicks, a former Iowa State University student, developed ammonia removal curves (Gullicks, 1987) that aided in the design of the facility's nitrifying trickling filters. The AWPCF is currently underloaded for ammonia receiving roughly 1/2 the 1,970 1bNH3-N/day that the facility was designed to treat. The facility removes ammonia to below 0.5 mgNH3-N/L. The city personnel would like to know whether the facility can remove ammonia to concentrations below the permit requirements if the plant is subjected to design loading conditions or higher. As the result, a study of nitrification at the AWPCF was initiated. Operating data coupled with data from an experimental study of the AWCPF were compared to Gullicks' original design curves, were used to calibrate the Gujer and Boller (1986) model, and were used to develop an empirical equation that predicts ammonia removal. The experiment required two major changes to the plant operations. The flow scheme at the AWPCF was changed to increase the ammonia loading on the trickling filters, and the hydraulic loading on the trickling filters was varied to provide a treatment variable. The results suggest that an empirical, response surface equation is most appropriate for predicting ammonia removal within the range of the operating and experimental data for the first stage trickling filters. The Gujer and Boller model is appropriate for the second stage trickling filters and extrapolating beyond the range of the data. Gullicks' design curves are most useful as a design tool. All three models have been calibrated for AWPCF trickling filters, and application in other facilities should not be performed without checking assumptions and treatment conditions. Based on model calibration, the AWPCF will be capable of removing ammonia at the design load given the operating conditions of this study. Though not designed for nitrification, the first stage trickling filters are removing a significant fraction of the ammonia load. Future studies on simultaneous treatment of biochemical oxygen demand (BOD) and ammonia in trickling filters are recommended.

Tue Jan 01 00:00:00 UTC 2002