Abstract: Large content of total nitrogen (TN) in the tail water discharged from industrial wastewater treatment plant is likely to cause eutrophication in surface water. In order to improve the removal efficiency of TN in the tail water, we investigated into the removal rate of TN by biofilm floating bed strengthened with different amounts of rice straw (0, 0.18 g/L, and 0.54 g/L) by simulated static and dynamic stabilization pond experiment. Static experiment result showed that the removal rate of TN increased significantly along with the increment of rice straw amount; after 10 days, the removal rate of TN was respectively 18%, 40%, and 93% when 0 (CK), 0.18 g/L (T1), and 0.54 g/L (T2) rice straw were added into the floating bed. Dynamic experiment result revealed that the mean TN removal rate of CK, T1 and T2 was respectively 10%, 22%, and 49% when the hydraulic retention time (HRT) was 4 d; no significant difference was found in COD concentration in the influent and effluent under the three conditions due to the fact that rice straw provides organic matter for heterotrophic denitrifying bacteria in biofilms by slowly releasing carbon source.

Key words: industrial tail water, rice straw, biofilm, floating bed, total nitrogen, COD