| The anaerobic ammonia oxidizing (Anammox) process has been put forward as an efficient and environmentally friendly technology to treat wastewater, though the majority of Anammox research are still in lab-scale. The extremely slowly growth rate of Anammox bacteria which causes rather long start-up period is the most obstacle in the application of the Anammox process. In addition, there are still many inhibitory factors such as heavy metals and organic matter that hinder the widespread application of the Anammox process.To solve these problems, the dissertation systematically investigated the effects of heavy metals (including Cd, Ag, Hg, Pb) and trace elements of Fe and Mn on Anammox bacteria. And on this basis, a promising alternative to enhance the activity and promote the growth rate of Anammox biomass was developed. Meanwhile, a mathematic model was developed for describing kinetics in the the simultaneous Anammox and heterotrophic denitrification (SAD) process as well as identifying the key operational factors and the most influential kinetic parameters. Some innovative conclusions have been made as follows:(1) Cd2+, Ag+, Hg2+ and Pb2+ could exert different levels of inhibition on Anammox bacteria. The nitrogen removal rate, hydrazine dehydrogenase (HDH) activity as well as heme c concentration were depressed after a 24-h exposure to those metals. Cd2+ and Hg2+ exerted sustained toxicity on Anammox biomass, but mal-effects of Ag+ and Pb2+ could resume to a large extent within 96 h. The order of the inhibitory effects was determined as Cd2+> Ag+> Hg2+> Pb2+(2) The appropriate increase of Fe2+ could enhance the nitrogen removal rate of Anammox bacteria with the elevated HDH activity and heme c synthesis. Continuous experiments demonstrated that the nitrogen removal rates elevated with increase of ferrous iron in range of 0.03-0.12 mM. The increased ferrous iron concentration also promoted heme c synthesis and HDH activity. The optimal Fe2+ concentration of 0.09 mM can elevate the nitrogen removal rate by 32.2% and shortened the start-up time of Anammox process by 28%. However, the increase of Fe2+ to 0.18 mM could depress Anammox bacteria activity and further deteriorate nitrogen removal performance.(3) The existence of MnO2 could relieve the adverse impacts on the Anammox bacteria from the substrates in high concentration, thus enhancing the maximum nitrogen loading rate, nitrogen removal rate and HDH activity of Anammox bacteria by 66.9%?98.2% and 76.7%, respectively. Furthermore, MnO2 addition also resulted in the structural changes of the cells.(4) A mathematic model was developed for describing the nitrogen and organic carbon removal via the simultaneous Anammox and heterotrophic denitrification (SAD) process.. Both the C/NO3-N and the population ratio of heterotrophic denitrifying bacteria to Anammox bacteria (XH/XAN) significantly affect the nitrogen removal performace of the SAD process. The C/NO3-N of 1.5-2.0 with the population ratio of XH/XAN of 0.3-0.4 were needed for a complete nitrogen removal. The most influential parameters in the SAD model were the ratio of half saturation constant for nitrite of heterotrophic bacteria to that of anammox bacteria (KNO2H/KNO2AN2) and the ratio of anoxic reduction factors of heterotrophic bacteria for the nitrate-reducing rate to that for the nitrite-reducing rate (?NOB/?NO2)... |
PDF Full Text Request