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Objective & Scope
1. Control of external carbon source addition in denitrification process Main Contents Biological removal of ammonia-N is widely employed in the treatment of coke plant wastewater which consists of carbon removal, nitrification and denitrification process. In the denitrification process, addition of external carbon source was required because of low COD/NOx-N ratio in wastewater. The addition of external carbon source should be rapidly controlled according to the fluctuation of nitrate concentration in the influent. The excessive addition of external carbon source could create anoterh problem such as high COD discharge in the final effluent. In this study, we introduced a control strategy of external carbon source addition in order to optimize the rate of denitrification and to stabilize COD discharge in the effluent. Two kinds of control regimes, on-off and feed-forward control, were introduced. The feed-forward control was based on the mass balance and dynamic model of denitrification process whereas the on-off control was simply connected to the level of nitrate in the denitrification stage. Although the on-off control could stabilize the level of nitrate and COD reasonably well in a general input mode, nitrite was accumulated when the loading rate of nitrate was high. This nitrite accumulation caused an inhibition of denitrification and accumulation of nitrous oxide which is another form of toxic waste. In the feed-forward control, we assumed that the COD concentration was proportional constant of COD/external carbon adn calculated to be 0.0336 by mass balance equations. In fact, this value was in the same order of magnitude with the experimental value (0.087). The feed-forward control gave stable concentrations of nitrate and COD in the effluent even at the severe fluctuation of nitrate concentration in the influent. References 1) Control of external carbon source addition in denitrification process Yun Jung Park, Thesis of Master (1997), POSTECH, KOREA 2) Control of external carbon addition in biological nitrogen removal process for the treatment of coke-plant wastewater M.W. Lee, Y.J. Park, J.M. Park, and H.D. Chun, Water Env. Res., 73(4), 415 (2001) |
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