- 日本水処理生物学会誌 (ISSN:09106758)
- vol.36, no.1, pp.25-31, 2000
Concentrations of nitrate and nitrite in groundwater are increasing year after year because of permeation of fertilizers and livestock drain into the ground. These nitrogen species may cause methemoglobinemia, whose characteristic symptom is cyanosis. In this study, an immobilized denitrifying bacterium was used to remove such nitrogen species from water. Ion-exchange resin, reverse osmosis membrane, electrodialysis and biological processes are the representative denitrification methods. These methods except for biological treatment cause trouble with the drain water. In biological treatment, there are two choices; autotrophic and heterotrophic denitrification. In both cases, nitrate is reduced to nitrogen gas by the bacteria. Heterotrophic bacterium requires organic carbon as the nutrient. Existence of organic carbon is not acceptable for treating drink water. In this study an autotrophic bacterium was, therefore, chosen to avoid using organic carbon.<BR>In this study, batch and continuous denitrifying experiments were carried out using <I>Paracoccus denitrificans</I>. The batch experiment was conducted in a 200m<I>l</I>-Erlemeyer flask containing 100m<I>l</I> of treating water and free or immobilized cells. The continuous experiment was carried out using a fixed bed bioreactor of 4.6cm internal diameter. In continuous denitrification, a packed bed of alginate-immobilized cells was used. In the continuous experiment, denitrification was successfully carried out for four hundred hours.