The Research On Denitrification Mechanism Of The Constructed Wetlands Used Vermiculite As Filling

The thesis investigates the possibility of the natural vermiculite to be the constructed wetlands filling; moreover, simulation experiment and the mechanism research for control the pollution because of the living waste water were done. It is the new area for the vermiculite application that the treatment technique of the vermiculite adsorption was applied to constructed wetlands. Recently, bio-regeneration of the filling is the hot point in the technique research on the constructed wetlands. This research contents mainly include:(1) the bio-film growing experiment of the natural vermiculite; (2) the parameter adjusted experiment of the intake with bio-vermiculite pole; (3) the mechanism explored experiment of the N removal of the bio-vermiculite pole.(1) the bio-film growing experiment on the natural vermiculite is shown as follows: It is easy for the natural vermiculite to be the carrier of the bio-film, becoming the bio-vermiculite, which comes into being the assimilation and transformation between the vermiculite and bacteria in 2-3 weeks. On the one hand there is the ion exchange adsorption to the ammonia nitrogen owing to the vermiculite; on the other hand, the adsorbed NH4+ can be transformed by the microbe, thus the ability of removal of the NH4+ for vermiculite can be greatly strengthened。(2) the parameter adjusted experiment of the intake bio-vermiculite is shown:the best effect can be gained under the given condition of pH=7.89, DO=5.40 mg/L, which makes the removal rate of the ammonia nitrogen and the total nitrogen best, 56.00%,45.00%, respectively. The normal living waste water can conveniently attain the condition of pH=7.89, DO=5.40 mg/L. So bio-vermiculite pole has the better treatment effect of removal of nitrogen under unnecessary extra adjustment of the intake parameter. The outtake can attain theⅡrank standard of the national waste water integrated outflow standard. The treatment effect in the summer is better than in the winter. All of them, it causes the removal of COD most remarkably affected from summer of 69.80% to 44.18% in winter, secondly, that of T-N from 45.00% of the summer to the winter of 30.00%, and then that of ammonia nitrogen from 44.00% by 55.00% of the summer. Meanwhile, the effect rate of the T-P is also hardly affected.(3) the mechanism explored experiment of the N removal for the bio-vermiculite is also shown:in the bio-vermiculite pole, the transformation of nitrogen doesn't agree with the traditional theory of the nitrification and the denitrification as well as the single and short process nitrification. According to the analyzing of the nitrogen balance and observing the experimental phenomena, the anaerobic ammonia oxidation, has happened in the pole. The condition of the high ammonia nitrogen at the vermiculite surface makes the reaction possible. However, the reaction of the traditional nitrification and denitrifi cation also happens in the pole. According to the results of determination, the most intensity of nitrification of the bio-vermiculite is 4.38×10-3 mg/g.h in the upper layer; that of the least in the middle is 0.63×10-3 mg/g.h, and 1.90×10-3 mg/g.h at the bottom. While the intensity of the denitrification in the pole is opposite against that of the nitrification, and the most intensity of denitrification is in the middle. Moreover the intensity of anaerobic ammonia oxidation is almost equal, average 1.00×10-3mg/g.h. This explains that the anaerobic ammonia oxidation bacteria grows in the bio-film endothecium, and the inner layer can not be affected by the organic substance and DO. According to the test results of VSS of the bio-film in the substance of the pole, the bio-film on the filling grows well, the average VSS 26.41 mg/g. Thus, as the carrier of the bio-vermiculite, the natural vermiculite plays a good adhering function. The results of counting the special function bacterium show that the amount of the denitrification and nitrification bacterium are little, at the floor level of the other investigation.The research results offer the theoretical support for the constructed wetlands used vermiculite as filling. At the same time, the indexes of biomass, the intensity reaction, the microorganism quantity, which can be the key index to measure the developmental degree of the constructed wetlands because of its special characteristic and function, are determined in this study, thus it is helpful to clarify the decontamination mechanism of the constructed wetlands and establish the evaluated the system. The discovery and validation concerning on verifications anaerobic ammonia oxidation reaction in the bio-vermiculite system make the field of current removal nitrogen on anaerobic ammonia oxidation reaction rich.