Potentials and limits of a pre-denitrification/ nitrification biofilter configuration for advanced municipal wastewater treatment.
Pre-denitrification in biofilters is limited by the amount of easily degradable organic substrate, resulting in relatively high requirements for external carbon. The combination of pre-DN, N and post-DN filters is much more advisable for most municipal wastewaters, because the recycle rate can be reduced and external carbon can be saved. For minimum use of external carbon, 100-150% recycle rate should not be exceeded. Then, approximately 50-60% of the total NO3-N can be depleted in the pre-DN stage. On average, 10 g total (t) COD/g NO3-N were required in the pre-DN stage for denitrification in the pilot and full-scale plant and 0.4-0.5 kg NO3-N/(m(3)DN d) can be reached without external carbon. As only 40-70% of the COD load is eliminated in the pre-DN, the remaining COD load is removed in the nitrification stage. 1 kg COD/(m(3) d) suppresses nitrification rates by approximately 0.1 kg NH4-N/(m(3) d). For nitrification rates, > 0.5 kg NH4N/(m(3) d) at 12 degrees C not more than 2 kg COD/(m(3) d) may be eliminated in the nitrification.
Rother
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Degussa AG, Bio- and Environmental Process Technology, Rodenbacher Chaussee 4, 63457 Hanau-Wolfgang, Germany. elmar.rother@degussa.com
Cornel
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D019149:Bioreactors; D005374:Filtration; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000378:metabolism
D009566:Nitrates; D014874:Water Pollutants, Chemical; D009584:Nitrogen