Research Of Sewage Deep Denitrification By Autotrophic Denitrification Filter Cell

As the eutrophication and nitrate pollution in surface and underground water has become more and more serious.Wastewater deep denitrification can effectively reduce the concentration of nitrate discharged into natural water,in which autotrophic denitrification is a hot spot in the present study.In order to reduce nitrate nitrogen wastewater treatment plant discharge,autotrophic denitrifying bacteria were screened and applied to deal with the secondary effluent of municipal wastewater.Three different strains?NT,NH,NW?of Thiobacillus Denitrificans were isolated from soil,bay sediments and anaerobic sludge by using Thiobacillus denitrificans selective media.Experiments used conical flask with enrichment media of Thiobacillus denitrificans in the culture conditions: initial p H 7.0,NO₃^--N 208mg/L,120r/min and 30?.The results show that strain NW has the best denitrification capacities which screened from anaerobic sludge exhibit,and the NO₃^--N and TN removal efficiency reaches 69.04% and 60% in 5 days.Through physiological and biochemical experiment,the strain was preliminary identified as Thiobacillus.After a series of single factor experiments of nitrogen removal performance,it showed that in the condition of p H 7.18,27.6? and initial S/N 1,the bacteria denitrification efficiency is the highest.The NO₃^--N removal efficiency is above 60% in the condition of p H6.5⁸.0 and range temperature of 20³5?,which illustrates that the strain NW has a strong ability to adapt to the environment.And when the concentration of NO₃^--N is in 0³00mg/L,nitrogen removal efficiency achieves 70%⁸5%.The activated bacterial suspension of strain NW was inoculated to the denitrifying biofilter in which filled 2⁵mm biological ceramsite as filler.The filter column adopted 100²00 mg/L nitrate concentration of influent water upflowing,and after 25 d of effluent operation,NO₃^--N removal efficiency reached 90%,which symbolized the filtration column hang membrane process was completed.And the autotrophic denitrification filter column operating parameters on the treatment effect of the simulate secondary effluent of municipal wastewater effluent nitrogen removal efficiency was studied.With the biological filter autotrophic denitrification,more than 90% of NO₃^--N and TN could be removed when the influent NO₃^--N concentration was over the range of 15⁵0mg/L.During the stable running period without the accumulation of NO2--N.The shortest HRT was 2h and the best removal efficiency was obtained at the influent NO₃^--N concentration of 30mg/L.Denitrifying denitrification rate is gradually increased along the filter height,NO₃^--N removal rate can reach 70% in loading height of 5cm.