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Observations from the First Year of Full-scale Operation - The IFAS/BNR Process at the Broomfield Wastewater Reclamation Facility, Broomfield, CO

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Motivated by pending discharge limits and capacity expansion needs, the City and County of Broomfield (Broomfield) examined several possible approaches to improve performance and increase the capacity of the Broomfield Wastewater Reclamation Facility (BWRF). Evaluation of the process alternatives suggested that retrofit of the existing aeration basins to integrated fixed film activated sludge (IFAS) to increase nitrification capacity coupled with biological nutrient removal (BNR) reactors for denitrification and phosphorus reduction was the most effective option. The designs for the new BNR basins and retrofit of the aeration basins to IFAS were completed in 2001. Construction of the new IFAS/BNR facilities began in the fall 2002 and completed by June 2003. The new IFAS/BNR process began uninterrupted service on July 1, 2003.

Extensive data collection by BWRF staff before and after the above-described improvements were made provided the authors with a unique opportunity to compare and contrast process performance. These comparisons focus primarily on ammonia removal and sludge settleability. In addition to these comparisons the data also provided the opportunity to observe trends in operations and performance during the past year of IFAS/BNR operation.

Observations from the first year of full-scale operation of the IFAS/BNR system show a significant improvement with regard to ammonia removal as compared to BWRF performance before the IFAS retrofit. There has also been a noticeable reduction in the effluent total suspended solids (TSS) as well as indications that the IFAS/BNR process has improved the settling character of the activated sludge.

Results from the first year of operation indicate that the design effluent quality objectives for nitrogen and phosphorus can be met with the IFAS/BNR process. However, BNR performance has been erratic due to the operation of just one of the two BNR trains during most of the evaluation period.

Routine monitoring of biomass attached to the plastic media shows that the equivalent mixed liquor contribution provided by the media is significant, ranging as high as 2,500 mg/L or more. The attached growth contribution is lower in the downstream reactors as compared to the upstream reactors. The attached growth contribution within a given reactor appears to change with seasonal variation of operating conditions.

Document Type: Research Article


Publication date: 2004-01-01

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