Research On Denitrification Effect And N₂O Production Of Anammox Biofilter

Anaerobic ammonium oxidation(anammox) technology is a new biological nitrogen removal process in these years, and it has the majority of prospects for development. However, the anaerobic ammonia oxidation process is mainly used for treating high ammonia wastewater, such as reject water, landfill leachate, etc., there is almost no information on municipal sewage using anaerobic ammonia oxidation projects. To promote anaerobic ammonia oxidation in municipal wastewater treatment applications, two biofilters with different filters have been studied for their nitrogen removal effect and some key process parameters. The reactor is 10 cm in diameter, 210 cm high using synthetic wastewater, which is to take the Bio-WWT effluent adding nitrite and ammonium, as influent and keeping the temperature at 34℃.Research on volcanic anammox biofilter, ①To investigate the startup of the biofilter column for anaerobic ammonia oxidation and denitrification performance after inoculation; ②Finding out the best filtration rate by gradually increasing the filtration rate; ③Using DO and pH as parameter to investigate the denitrification performance in different filter layer level; ④Backwashing research; ⑤To investigate the production of N2 O in different filtration rate. In order to do comparison with volcanic anammox biofilter, while the ceramic anammox biofilter has also been studied with the same factors.The obtained results showed that the anammox biofilm in both biofilters was successfully cultivated after 10 days of inoculation. Filter media and backwash both played important role on achieving stable anammox in biofilter. On the condition of low filtration velocity, in both biofilters, not only nitrogen removal rate was almost similar, but also water backwash and long backwash cycle were optimal. However, under high filtration velocity, volcanic biofilter was more easily blocked up than ceramic biofilter. The effective depth of filter layer in volcanic biofilter was also thinner than that in ceramic biofilter. Besides, air + water backwash style was optimal, backwash cycle should be shorten and backwash time should be prolonged. The highest nitrogen removal loading rate in volcanic biofilter and ceramic biofilter was 3.81 kg/(m3·d) and 3.56 kg/(m3·d), respectively. Nitrous oxide(N2O) can be detected in the gas production when filtration rate is greater than 1m/h, and N2 O production increased with the filtration rate increasing. When the filtration rate is 3m/h, the gas production in volcanic biofilter and ceramic biofilter was 2.49L/h and 1.73L/h, respectively. The dissolved N2 O concentration is 0.65mg/L in the effluent of volcanic filter, the concentration of N2 O gas is 1094 ppm. Correspondingly, the dissolved N2 O concentration is 1.05mg/L in the effluent of volcanic filter, the concentration of N2 O gas is 689 ppm. Considering the greenhouse gases and nitrogen removal effect between these two filters, the best filtration rate of these two filters is 2.5m/h.