Biological upflow fluidized bed denitrification reactor demonstration project - Stamford, CT, USA

The discharge of nitrogen in wastewater treatment plant effluent has been identified as a receiving water quality issue throughout the United States and in the European Community. Regulatory agencies are evaluating discharge limits for total nitrogen (TN) as low as 3 to 5 mg/l. To attain these limits at treatment plants with little or no space for expansion, technologies which can remove large quantities of nitrogen with relatively small space requirements are required. Biological upflow fluidized bed (BFB) technology appears to be well suited to these regions. This paper describes the results of a demonstration project using a fluidized bed reactor. The reactor was operated at a flow rate of 15 l/s and an average daily loading of 1843 kg NO₃/1000 m³/d and maximum loadings of 6407 kg NO₃/1000 m³/d. At steady-state conditions, effluent total nitrogen concentrations averaged 2.5 mg/l over a temperature range of 11 to 25°C. At high nitrate loading rates, effluent total nitrogen concentrations averaged 4.1 mg/l. Approximately 3 mg of methanol per mg of influent nitrate was used as a carbon source. Reactor empty bed contact time averaged 5.7 minutes.