Investigating upflow biofiltration using the Biostyr process by varying the organic strength of the influent

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Virginia Tech


The performance of Biostyr media using an upflow biofilter scheme was investigated. Three separate Modes that varied the organic strength of the influent at an operating temperature of 12°C were evaluated to explore how nitrification and denitrification responded to different concentrations of biodegradable COD loadings. Effluent suspended solids and observed yield coefficients were also analyzed along with ways to determine kinetic parameters. Combinations of primary and secondary effluent were used as the influent using domestic wastewater from a primary sewer of the Blacksburg VPI Sanitation Authority, in Blacksburg, Virginia, located on the Virginia Tech Campus.

Reduction of nitrification rates was observed in the aerobic reactor at biodegradable COD loadings to the aerobic biofilter of 2.2 kg/day/m³ and greater. Complete denitrification was observed in the anoxic tank at biodegradable COD loadings to the anoxic biofilter of 7.5 kg/day/m³ and greater. Above this value, denitrification was limited by the available amount of NOx-N. An optimum influent biodegradable COD loading rate of 7.5 kg/day/m³ to the anoxic biofilter and 2.2 kg/day/m³ to the aerobic biofilter was experimentally demonstrated for simultaneous nitrification and denitrification.

When secondary effluent was fed to the reactors, complete nitrification was observed indicating success in terms of ammonia polishing. However, low concentrations of influent biodegradable COD limited the ability for the anoxic reactor to denitrify. Thus, it was determined that the addition of an external carbon source would need to be implemented to denitrify when using low strength secondary effluent.

Effluent total suspended solids were consistently below 20 mg/L indicating that secondary clarification would not be needed for this reactor scheme. The combined observed yield was consistently around 0.2 (mg-VSS/mg-COD consumed) or less. However, the evaluation of separate anoxic and aerobic yields was inconsistent when averaging data over 5 days, because of the recycle of biomass from the aerobic reactor back to the anoxic reactor.

The kinetic parameters, q'MAX NIT and K’S NIT were calculated by plotting nitrification rates as a function of ammonia concentration. These coefficients were calculated by using separate segments within the media under less than optimal conditions. It was determined that analyzing the whole system rather than segments would be better suited for kinetic parameter analysis. However, there was not enough collected data to achieve this. Thus, ranges identifying further influent biodegradable COD loadings were recommended for later research to better a complete kinetic parameter evaluation.



Biostyr, upflow, biofiltration, nitrification, fixed-film