| In this study,sulfur was added to the autotrophic denitrification system of pyrrhotite to strengthen its denitrification capacity,and the autotrophic denitrification system combining pyrrhotite with sulfur can also improve the effluent sulfuric acid of the autotrophic denitrification system to a certain extent.Insufficient salt concentration too high.In the experiment,two reactors,B1(Fe1-xS)and B2(S0+Fe1-xS),were built,the effect of combining pyrrhotite with sulfur to assist the start-up of the reactor was explored,and the autotrophic reaction of pyrrhotite was analyzed in depth.Nitrogen and phosphorus removal performance of nitrification system for low C/N secondary effluent.At the same time,the nitrogen and phosphorus removal performance of the system in the actual secondary effluent is discussed to provide support for the development of a more economical and effective secondary effluent advanced treatment process.The main research results are as follows:（1）B1 and B2 were successfully started on the 20th and 21st days,respectively.The nitrate removal rate of B2 was about 30%higher than that of B1.The start-up effect of the composite matrix reactor B2 was better,achieving the effect of adding sulfur to optimize the start-up of a single pyrrhotite system.The longer the HRT,the better the denitrification effect.When HRT=12 h,B2 can remove 20 mg NO3--N/L100%,while the removal rate of B1 is only 68.6%.When the influent NO3--N load is increased,the B2 removal load also increases,while B1 has no significant change;when the influent NO3--N load is 0.072 kg/（m3·d）,the B2 treatment load is 0.063kg/（m3·d）,while B1 is only 0.029 kg/（m3·d）.The phosphorus removal rate of B2 in each stage is higher than 90%,and B1 is also close to 90%.In different HRT and influent nitrate concentration tests,the denitrification and phosphorus removal effects of B2 were better than that of B1,and the addition of sulfur enhanced the denitrification performance of the pyrrhotite autotrophic denitrification system.（2）The proportion of denitrification contribution in the sulfur-pyrrhotite composite matrix reactor changed significantly,and the proportion of sulfur autotrophic denitrification decreased from the initial 95%to 4%.There are three processes in which the first matrix is dominated by sulfur,to the"co-substrate"of sulfur and pyrrhotite,and then to the"second matrix"of pyrrhotite.（3）The diversity of microbial community in B1 was higher,while the stability of microbial community in B2 was higher.The common dominant bacterial phyla of B1and B2 are Proteobacteria and Chloroflexi,and the common dominant bacterial genus is Thiobacillus;the top three proportions of core microorganisms at the genus level of B1 and B2 are Thiobacillus,Ferritrophicum and SBR1031,and the sum of the three proportions is in B1 and B2 were 14.53%and 52.58%,B2 was much higher than B1.（4）Adding carbon source to the reactor B1,when the COD concentration is 57.2mg/L,the effluent nitrate concentration can be reduced to 6.65 mg/L,and the addition of sodium acetate can effectively improve the shortcomings of low processing load of the single substrate reactor,the heterotrophic production of alkalinity is complementary to the autotrophic acid production,and will not affect the phosphorus removal effect of the system.However,while the mixed denitrification improves the denitrification efficiency,it also increases the COD concentration of the effluent,which will cause secondary pollution.（5）For the actual secondary effluent,the denitrification and phosphorus removal effect of B2 is better than that of B1;the COD of the actual secondary effluent is mainly refractory humus,and the COD removal is not obvious;the effluent still has excellent stability,and no additional adjustment is required.pH.The sulfur-pyrrhotite autotrophic denitrification system has certain value in the application of advanced treatment of actual secondary effluent. |
PDF Full Text Request