Research On The Effect Of Chloroorganics On Nitrogen Removal Of Simultaneous Nitrification And Denitrification And Bacterial Community Structure

In the process of biological treatment of actual wastewater,the efficiency of the target pollutants such as nitrogen and phosphorus can be affected by some refractory organic matter,thereby affecting water quality.Therefore,this study firstly implemented simultaneous nitrification and denitrification(SND)technology in an efficient sequential batch biofilm reactor(SBBR)to construct a new biological denitrification process SND-SBBR.Then taking SND-SBBR as the research object,the effect of different concentrations of2,4,6-trichlorophenol(TCP)and chloramphenicol(CAP)on the nitrogen removal performance of SND-SBBR and the biodegradation efficency of these two organics were investigated.Finally,the high-throughput sequencing methods was used to characterize the changes of bacterial community structure caused by 2,4,6-TCP and CAP.(1)Results indicated that 2,4,6-TCP inhibited the nitrification with the decrease in ammonium nitrogen removal,and the average removal efficiency decreased by 9.27 mg/L.However,2,4,6-TCP had different effect on denitrification.Nitrate accumulation showed the tendency to decrease first and then increase,with a change of 3.42 mg/L.But nitrite accumulation showed the opposite change,and the change was only 0.095 mg/L.At the same time,the results showed that 25 mg/L 2,4,6-TCP had the greatest effect on SND-SBBR,and the longest time of adaptation and recovery was 42 days.In addition,the process had a good degradation effect on 2,4,6-TCP,of which 25 mg/L 2,4,6-TCP had the best degradation efficiency,with an average degradation efficiency of 23.10 mg/L.And in the SND-SBBR,2,4,6-TCP was mainly reduced to 2,4-dichlorophenol(DCP).With the increase in 2,4,6-TCP concentration,the differences in the bacterial community in the reactor were significant.For example,at the phylum level,2,4,6-TCP inhibited the growth of the denitrifying bacteria,such as the Proteobacteria and Bacteroidetes,and their abundance decreased by 34.08% and6.38% on average.(2)CAP also inhibited nitrification and reduced ammonium nitrogen removal by 7.35mg/L on average,but the inhibition was weaker than that caused by 2,4,6-TCP.Different concentrations of CAP showed inhibition on denitrification as a whole,and the effect onnitrate accumulation was greater than that on nitrite accumulation.The accumulation of nitrate was generally on the rise,with an average increase of 4.86 mg/L.The accumulation of nitrite generally showed a downward trend,with an average decrease of 0.017 mg/L.The results also showed that the 15 mg/L CAP had the least effect on SND-SBBR,and the shortest adaptation and recovery time was 14 days.In addition,the process had a good degradation effect on CAP,and the biological removal efficiency increased with the increase in CAP concentration.The 20 mg/L CAP degradation effect was the best,and the removal efficiency was 19.466 mg/L.Simultaneously,variations in CAP concentrations also caused significant differences in bacterial community in the reactor.For example,the abundance of the dominant phylum Proteobacteria decreased in general,but the abundance of Firmicutes increased.