NITROGEN REMOVAL FROM THE EUTROPHICATED WATER SYSTEM BY MICROBIAL-PLANT INTEGRATED SYSTEM

摘要

The floating macrophyte—Eichhornia crassipes and submerged macrophyte—Elodea nuttallii have different potential uses in purification of eutrophicated water. It is not known how the nitrogen removal efficiency of these aquatic plants may be influenced by inoculation with immobilized nitrogen-cycling bacteria (ammonifying, nitrosation, nitrifying and denitrifying bacteria). When inoculated into the water system, the populations of the nitrosation, nitrifying, and denitrifying bacteria increased 1 to 2 orders of magnitude compared to the un-inoculated treatments, but ammonifying bacteria showed no obvious difference in proliferation among different treatments. The treatment combining floating macrophyte with bacterial inoculation resulted in a decrease in total nitrogen from 1.1 mg/L to 0.52 mg/L during the experimental period, and the concentration of ammonium and nitrite was also lower than in other treatments, whereas the water transparency increased from 0.5 m to 1.8 m. The number of ammonifying bacteria was from 10~5 to 10~7 per millilitre, and numbers of nitrosation, nitrifying and denitrifying bacteria fluctuated from 10~(2.5) to around 10~5 per millilitre. The treatment combining submerged macrophyte and bacterial inoculation showed the total nitrogen decrease from 1.4 mg/L to 1.1 mg/L, and more than doubling of water transparency to 1.2 m at the end of experiment The numbers of nitrogen-cycling bacteria in combination with the submerged macrophyte were lower than in the treatment with floating macrophyte, fluctuating between 10~4 and 10~5 (ammonifying bacteria) or 10~1 to 10~(3.5) per millilitre (nitrosation, nitrifying and denitrifying bacteria) and being higher than in the treatments with bacterial inoculation only. We conclude that the size of populations of various nitrogen-cycling bacteria influences the nitrogen concentration and the other quality parameters of the eutrophicated water and that Eichhornia crassipes (summer-autumn floating macrophyte) has a greater capacity to purify the eutrophicated water than Elodea nuttallii (winter-growing submerged macrophyte). This paper contributes to a basic theory of pathways of nitrogen removal from the eutrophicated water using integrated microbe-plant system.