Study On The Screening And Cultivation Of Highly Efficient Nitrosifying Bacteria And The Degradation Characteristics Of Ammonia

In recent years,new denitrification technologies such as short-cut nitrification and denitrification,and short-cut nitrification and anammox have been widely used.They have the advantages of highly-efficientey denitrification,low energy consumption and high removal rate.The accumulation of nitrite nitrogen is the difficulty for the stable application of the new denitrification technologies,the key is to screen and cultivate nitrosating(AOB).However,most of the currently screening and cultivation AOB were used in laboratory water distribution,and there is a lack of applied research on actual pharmaceutical wastewater.In this study,aerobic activated sludge collected from three pharmaceutical wastewater treatment plants(A、B、C)was used as the source of bacteria,Shake flasks were used for the nitrosating bacteria screening and cultivation pruposes,A mixed flora was construct and the cultivation was expanded to obtain the bacteria agent;The effects of environmental factors on the activity of the bacteria agent were investigated,and eventually,pharmaceutical wastewater was used to verify the function of the ammonia nitrogen degradation function of the bacterial agent.The main research contents are as follows:(1)After about 50 days of screening and cultivation,the accumulation rate of nitrite nitrogen in the system of the three source bacterial groups exceeded 85%.Three microbial communities with stable nitrosation function were successfully screened and cultivated.The three microbial communities were mixed and subjected to expanded cultivation.During the cultivation,the nitrosation rate increased from 4.44 to 11.99mg/(L·h),while the MLVSS of the mixed flora increased from 17.8 to 320 mg/L,As a result,the nitrosating bacterial agent D was obtained.(2)At the end of the screening and cultivation.The dominant phylum was found to be the Proteobacteria for the three source bacterials(A-2、B-2、C-2)and the bacterial agent D,with the relative abundances being 82.8%,73.3%,94.7%,and 80.20%respectively;The dominant genus was Nitrosomonas,which belongs to Proteobacteria,It’s relative abundances in the bacterials was 61.7%,54.9%,69.1%,and 63.22%,respectively;The OTU with the highest relative abundances among the three source bacterials and bacterial agent D was OTU1,and the similarity between OTU1 and Nitrosomonas europaea reached 100%.Nitrosomonas with highly relative abundance,which ensures that the bacterial flora can carry out a efficient and stable nitrosation reaction in the water.(3)The influence of environmental factors on the nitrosation performance of bacterial agent D.The specific ammonia oxidation rate in the system gradually increased with the increase of ammonia nitrogen concentration.With an ammonia nitrogen concentration of about 300 mg/L,the specific ammonia oxidation rate reached the maximum value of 2.99 g N/(g VSS·d).the ammonia nitrogen degradation rate in the system gradually increased with the increase of temperature.The maximum removal rate(95%)of ammonia oxygen was achieved at 30 ℃.It was also found that,the nitrosation intensity in the system decreased linearly with salinity.Specifically,the removal rate of ammonia nitrogen was 95% at zero salinity,and it dropped significantly to 13% when the salinity was increased to 20 g/L.It can be seen that the optimum temperature and ammonia nitrogen concentration of the bacterial agent are 30°C and300 mg/L,respectively,and the bacterial agent activity is inhibited in high-salt wastewater.(4)Bacterial agent D,activated sludge,and mixed activated sludge and bacterial agent D,were added respectively to the anaerobic effluent of pharmaceutical wastewater(avermectin,lincomycin,and mixed effluent)to verify their ammonia nitrogen degradation functions.In the application of bacterial agent D,the specific ammonia oxidation rates of the three types of pharmaceutical wastewater were 2.39,1.24,0.54 g N/(g VSS·d),the removal rates of ammonia nitrogen were 96.22%,95.8%,and 94.7% respectively,with the accumulation rate of nitrite nitrogen beings above85%;In the application of activated sludge,the ammonia nitrogen concentration of the three types of pharmaceutical wastewater did not decrease but increased instead;In the application of mixed activated sludge and bacterial agent D,the specific ammonia oxidation rates were respectively 1.18,0.45,0.26 g N/(g VSS·d),in the three types of pharmaceutical wastewater,and ammonia nitrogen removal of the rates were 93.5%,94.4%,and 99.6% respectively,and the accumulation rate of nitrite nitrogen was above85%;In the presence of baacterial agent D,the specific ammonia oxidation rate in the abamectin pharmaceutical wastewater was much faster than those in the other two types of pharmaceutical wastewater.Moreover,the indigenous bacteria had less influence on the overall performance.