| dc.description.abstract | This research conducts the batch heterotrophic denitrification experiments of active sludge from science industrial park, and the batch autotrophic denitrification experiments by acclimated sludge. The denitrification characteristics and the kinetic description of the denitrification process are also evaluate.
The research results show that when using acetate as an additional carbon source for denitration, the denitration rate is about 2 to 3 times that of methanol and molasses as the carbon source. When using acetate and molasses as additional carbon sources for denitrification, nitrite, which is an intermediate product of denitrification, will accumulate during the denitrification process, at the same time, it is observe that the concentration of ammonia nitrogen decreases. Moreover, if used molasses as an additional carbon source, when the COD loading increases, nitrite concentration will increase at the same time. Using acetate as an additional carbon source have 90% of the external carbon source removal ratio in 8 hours, while methanol and molasses are only 40%, there have COD residual in the effluent obviously.
The denitration kinetic of using methanol and C/N ratio 3 and 4 of acetate as an additional carbon source have no significant difference between the fitting of 0-order and 1-order function in analysis of variance. Using molasses as an additional carbon source is fit to 1-order function. While using C/N ratio is 5 or 6 of acetate as an additional carbon source is fit to 0-order function. It is speculate the denitrification kinetics of molasses is the restriction by the biological metabolic characteristics of carbon sources, that it presents 1-order denitrification kinetics. While using C/N ratio is 5 or 6 of acetate as an additional carbon source, the carbon source metabolic characteristics and concentration are not the restriction, that it present the 0-order denitration kinetics.
The autotrophic denitrification organisms can remove 100 mg/L of nitrate nitrogen within 12 hours after operating under the acclimated conditions in this study for about one month. In autotrophic denitrification experiments, when nitrate is added less than 100 mg/L, it can be completely remove within 8 hours. However, each experiments batch produces high concentration nitrite. During the autotrophic denitrification, data shows that the oxidation quantity of thiosulfate is more than the production of sulfate when the daytime.
Nitrate concentration change in the autotrophic denitrification is fit to 1-order function, while thiosulfate concentration change is fit to the 0.5-order reaction. It is speculate that in the autotrophic denitrification process, the denitrification kinetic order is affected by the metabolic characteristics of thiosulfate and the excessively high concentration of nitrite. | en_US |