Process Consideration to Achieve Nitrogen Removal in a Moving-Bed Biofilm Reactor

Blue Plains AWTP
Washington, District of Columbia

The MBBR process is a relatively new biological attached growth treatment system for denitrification. The results of this research should improve the understanding and quantification of the important kinetic and stoichiometric parameters of the MBBR system. The following conclusions can be drawn from overall test results:
i. Biomass density test indicated an increase in biomass density with decrease in temperature. Observed values ranged widely from 6 – 22 g/m2 for R1 and 5-17 g/m2 for R2 throughout the test period (January through June, 2008) for temperatures ranging from 11oC to 24oC.
ii. SDNR was estimated between 1.3 to 2.0 g N/m2/d expressed in terms of total biofilm carrier area. The SDNR expressed as g/m2.d had very little relationship with temperature suggesting a resilience of the overall process to temperature changes. The SDNR expressed as g-NOx- N/g biomass-d was observed to decrease with decreasing temperature. This suggested an Arrhenius relationship, and the Arrhenius constant was calculated as 1.09 for R1 and 1.07 for R2 for a temperature range of 11 – 18 oC, similar to those observed for the activated sludge process using methanol as a substrate. The biomass accumulation at colder temperatures may have contributed to temperature-stable SDNRs when expressed as g/m2.d. This is of practical significance for use of MBBRs in colder climates.
iii. Stoichiometric COD/N ratio was observed in the range of 4.6 mg COD/mg NO3-N to 5.3 mg COD/mg NO3-N and 4.4 mg/mg to 6.1 mg/mg for R1 and R2 respectively. This range is similar to the range observed for denitrification in suspended growth processes.
iv. A model was developed to predict half saturation constant for the MBBR biofilm. The model was based on the non-linear Monod kinetic model and operated on a Microsoft Excel Platform. The model predicted a similar range of KsNOx-N between 0.6 and 2.6 mg N/L for R1 and R2. These values seemed insensitive to changes in temperature with a weak relationship with biomass density.                                                                     Source: WEFTEC 2009 Proceedings

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Posted: July 6th, 2010 | Filed under: Waste Water Treatment | Tags: Nitrogen Removal, Sustainable Technologies | No Comments »

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