摘要
River waters in China have dual contamination by nutrients and recalcitrant organic compounds. In principle, the organic compotmds could be used to drive denitrification of nitrate, thus arresting eutrophication potential, if the recalcitrant organics could be made bioavailable. This study investigated the potential to make the recalcitrant organics bioavailable through photocatalysis. Batch denitrification tests in a biofilm reactor demonstrated that dual-contaminated river water was short of available electron donor, which resulted in low total nitrogen （TN） removal by denitrification. However, the denitrification rate was increased signifi- cantly by adding glucose or by making the organic matters of the river water more bioavailable through photocata- lysis. Photocatalysis for 15 min increased the Chemical Oxygen Demand （COD） of the river water from 53 to 84 mg. L-1 and led to a 4-fold increase in TN removal. The increase in TN removal gave the same effect as adding 92 mg.L 1 of glucose. During the photocatalysis experi- ments, the COD increased because photocatalysis trans- formed organic molecules from those that are resistant to dichromate oxidation in the COD test to those that can be oxidized by dichromate. This phenomenon was verified by testing photocatalysis of pyridine added to the river water. These findings point to the potential for N removal via denitrification after photocatalysis, and they also suggest that the rivers in China may be far more polluted than indicated by COD assays.
River waters in China have dual contamination by nutrients and recalcitrant organic compounds. In principle, the organic compotmds could be used to drive denitrification of nitrate, thus arresting eutrophication potential, if the recalcitrant organics could be made bioavailable. This study investigated the potential to make the recalcitrant organics bioavailable through photocatalysis. Batch denitrification tests in a biofilm reactor demonstrated that dual-contaminated river water was short of available electron donor, which resulted in low total nitrogen （TN） removal by denitrification. However, the denitrification rate was increased signifi- cantly by adding glucose or by making the organic matters of the river water more bioavailable through photocata- lysis. Photocatalysis for 15 min increased the Chemical Oxygen Demand （COD） of the river water from 53 to 84 mg. L-1 and led to a 4-fold increase in TN removal. The increase in TN removal gave the same effect as adding 92 mg.L 1 of glucose. During the photocatalysis experi- ments, the COD increased because photocatalysis trans- formed organic molecules from those that are resistant to dichromate oxidation in the COD test to those that can be oxidized by dichromate. This phenomenon was verified by testing photocatalysis of pyridine added to the river water. These findings point to the potential for N removal via denitrification after photocatalysis, and they also suggest that the rivers in China may be far more polluted than indicated by COD assays.
基金
Acknowledgements The authors acknowledge the financial support by the National Natural Science Foundation of China （Grant Nos. 50978164 and 50678102）, the Major Science and Technology Program for Water Pollution Control and Treatment （No. 2009ZX07313-003）, the Innovation Fund for Key Projects of Shanghai Municipal Education Commission （No. 10ZZ82）, the Special Foundation of Chinese Colleges and Universities Doctoral Discipline （Nos. 20113127110002 and 20070270003）, the Shanghai Leading Academic Discipline Project （No. S30406）, and the United States National Science Foundation （No. 0651794）.
