Study On Denitrification Performance Using Different Kinds Of Solid-phase Carbon Sources

Groundwater is widely used as resource for human being in the world. Despite the large amount of water resource in our nation, per capita consumption of water is less than the 1/4 of world average, owing to large population. So the shortage of water and pollute are serious problem in our nation. Biological treatment has the characteristics of high efficiency and low consumption. The purpose of this experiment is to test by batch and column experiments of different solid organic carbon for denitrification. This experiment studies the stimulation of different kinds of solid-phase carbon source for denitrification process through batch tests and column experiments, and researches the influence of influent nitrate concentration on denitrification, providing an important theoretical basis for the groundwater remediation.To study the effect of different solid carbon source during the denitrification process, wheat bran, straw, rice bran and biodegradable plastics can be used as solid-phase carbon source in the denitrification. The experiment is divided into two stages. First stage is the batch experiments of denitrification, aiming at studying the release of the solid-phase carbon source itself and the changes of nitrates, nitrites and ammonia, and ultimately selects the suitable solid-phase carbon source. The second stage is denitrification column experiment, in which using the simulation of the actual groundwater flow conditions, adding wheat bran, rice bran and biodegradable plastic as solid-phase carbon source, to further contrast the three kinds of solid-carbon source of nitrate nitrogen removal efficiency and ammonia nitrogen and nitrate nitrogen accumulation in the process during the column experiment. The outcome of the experiment shows that biodegradable plastic, with a high nitrate removal efficiency of 99.5% is the most suitable solid-phase carbon which showed the best effect for the promotion of denitrification owing to the lower amount of nitrogen compounds released, also with lower accumulation of nitrite. Followed by is rice bran, the nitrate removal efficiency is 78%. When using wheat bran and straw as solid-phase carbon source, the nitrate removal efficiency is only 29.9% and 18.8%. Further experiment also shows when water nitrate concentration increases within a certain range, the nitrate removal efficiency will be higher. In the column experiment, each solid phase carbon adsorption experiment shows that biodegradable plastics are almost no adsorption of nitrate, while the wheat bran and rice bran has certain adsorption on water nitrate. At the beginning of the column experiment, wheat bran and rice bran as solid-phase carbon source, the nitrate removal efficiency is obvious mainly due to its adsorption. The maximum adsorption capacities are 97.7%, 99.7%, respectively. In the groundwater denitrification column experiments, when using biodegradable plastic as solid-carbon source, the removal efficiency is not as ideal as batch experiments, which reaches only 33.3%. During the denitrification process, the accumulation of nitrate nitrogen using biodegradable plastics is higher than the wheat bran and rice bran, the peak is 8.5 mg/L, while the ammonium nitrogen accumulation in the whole process is lower, maintaining around 0.91 mg/L. The nitrate removal efficiency of wheat bran and rice bran are 66.4% and 67.2%, wheras nitrite accumulation are 0.15 mg/L and 0.14 mg/L, correspondingly ammoniun accumulation are5.16 mg/L and 6.17 mg/L, respectively. Moreover, column experiment also shows that the nitrate removal using rice bran as solid-carbon source is a good choice. It is cheap with a high removal efficiency of 67.2%, and the nitrite nitrogen and ammonium nitrogen accumulation in the process of denitrification are relatively low, so it is a good choice for the actual processing of groundwater remediation.