A NOVEL APPROACH FOR MONITORING AND CONTROL OF DENITRIFICATION IN A BIOLOGICAL NUTRIENT REMOVAL FACILITY

摘要

The Reedy Creek Improvement District抯 (RCID) wastewater treatment facility is afive-stage modified-Bardenpho process comprised of four parallel trains eachdesigned to treat 6 MGD. Due to innovative procedures implemented by theengineering and operational staff, the bioreactor has been operating at near 200% ofits design treatment capacity, which has led to substantial cost savings. While nitrogenremoval is satisfactory under current loading rates, our experience with this facilitysuggests that a lack of carbon in the second anoxic zone will limit denitrification andbecome a bottleneck to increased treatment capacity in the future. We believe that ifwe can develop an effective control strategy for adding a carbon source to optimizedenitrification at higher flows, a single bioreactor train could treat up to 15 MGD.External carbon sources, such as methanol, are commonly used to enhancedenitrification in advanced wastewater treatment facilities. Despite the financial andcompliance implications, there exist few good options for metering carbon additions.For this study we evaluated the effectiveness of using on-line data from a 'BiologicalActivity Meter' (BAM) to establish a protocol for adding ethanol into the second anoxiczones of the RCID bioreactor and a pilot-scale version of the bioreactor. The additionof ethanol increased the denitrification rates in both plants, and the BAMs were ableto detect subtle changes in these rates. By using the BAM data to guide manualaddition of ethanol, we reduced consumption significantly over using a constantaddition rate (25% and 17% in the full-scale and pilot-scale plants, respectively) whilemaintaining very low effluent nitrate concentrations in both plants.