Zum Einfluß von Sauerstoffkonzentration und pH-Wert bei der heterotrophen Denitrifikation Heterotrophic Denitrification: The Influence of Oxygen and pH Value |
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| Authors: | W Merkel E Bhler F H Frimmel |
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| Institution: | W. Merkel,E. Böhler,F. H. Frimmel |
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| Abstract: | A demonstration plant for biological heterotrophic water treatment of nitrate polluted groundwater has been operated in Coswig near Dresden since 1989. In this NEBIO tube reactor process the denitrification is achieved in a downstream fluidized bed with continuous regeneration of sintered polystyrene particles as inert carrier material. A nutrient consisting of ethanol and phosphate is dosed in the reactor influent. In the subsequent treatment stages the denitrified water is aerated, filtered through a multilayer and GAC filter, and is finally disinfected with chlorine gas. The influence of changing raw water quality (oxygen content, pH value) on the process performance was examined. Increasing oxygen concentration lowers the nitrate reduction potential and rises the consumptive ratio ΔC/ΔNO3. The technology shows a high removal performance of 270 g NO3 m?3 h?1 in the range of pH 6.2 to pH 7.3 which is typical for natural groundwaters. The degradation of nitrate is increasingly inhibited for pH values beyond 7.6. Nitrite production occurs significantly in high pH ranges. The results lead to further insight in the stoichiometry of heterotrophic denitrification. By expressing the stoichiometric equations for nitrate and oxygen respiration as functions of oxygen and pH value it could be shown that the influent water quality has strong effects on the consumption of ethanol. A kinetic model was developed to predict the reactor performance under changing raw water conditions. A two stage kinetic model was designed, regarding two main effects: biochemical degradation of oxygen, nitrate and ethanol and distribution of active biomass due to hydraulic properties of the tube reactor. This model may be helpful for reactor design for sites of various ground water qualities. |
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| Keywords: | Biologische Trinkwasseraufbereitung Wirbelschichtreaktor heterotrophe Denitrifikation NEBIO-Rohrreaktor-Verfahren |
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