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Denitrification Kinetics and Stoichiometry of a Moving Bed Biofilm Reactor Using Methanol as an External Carbon Source Open Access

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The primary objective of this research was to better understand the denitrification kinetics and to determine kinetic and stoichiometric parameters for nitrogen removal of a MBBR( Moving Bed biofilm Reactor) system. Mainly, four parameters: specific denitrification rate (SDNR), half saturation constants (Ks) of limited NOx-N and Chemical Oxygen Demand (COD) and biomass density were measured over a range of temperatures of four individual reactors namely T1R1, T1R2, T2R1 and T2R2 that resembled the small scale pilot reactors located in the Blue Plains Advanced Wastewater Treatment Plant, Washington, D.C. Average SDN rate of reactors T1R1, T1R2, T2R1 and T2R2 was estimated as 1.67 g NOx-N/m2/d, 1.47 g NOx-N/m2/d, 1.50 g NOx-N/m2/d and 1.28 g NOx-N/m2/d respectively. The SDNR expressed as g/m2/d exhibited very little relationship with temperature suggesting a resilience of the overall process to temperature changes. SDN rate expressed in terms of g NOx-N/g biomass/d were estimated as 0.07-0.18 for T1R1 at a temperature range of 12&degC-20;&degC; 0.10-0.20 for T1R2 and 0.07-0.13 for T2R2 at a temperature range of 13&degC-18;&degC;, and 0.07-0.12 for T2R1 at a temperature range of 12.5&degC-20;&degC.; The SDNR expressed as g NOx-N/g biomass-d was observed to decrease with decreasing temperature suggesting an Arrhenius relationship and the Arrhenius constant (μ) was calculated as 1.08. for T1R1 and 1.07 for T1R2 for a temperature range of 12&degC; - 20&degC.Similarly;, stoichiometric COD/N ratio was estimated in the range of 4.6 mg/mg to 5.3 mg/mg, 4.4 mg/mg to 6.1 mg/mg, 4.3 mg/mg to 6.3 mg/mg and 4.3 mg/mg to 5.9 mg/mg for T1R1, T1R2, T2R1 and T2R2 respectively. This range is similar to the range observed for denitrification in activated sludge suspended growth process.Ks values for limited NOx-N were estimated between 0.61-2.55 mg N/L and 0.64-2.60 mg N/L, and for limited COD between 6.3-12.7 mg/L and 4.4-12.3 mg/L for T1R1 and T1R2 reactors respectively. Biomass Density values ranged widely from 6-21.6 g/m2, 4.37-16.52 g/m2, 7.46-20.48 g/m2 and 5.39-17.65 g/m2 for T1R1, T1R2, T2R1 and T2R2 reactors respectively for a temperature range of 11&degC-23.5;&degC.; The test indicated increase in biomass density with decrease in temperature.

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