| Filler is one of the technical cores affecting the sewage purification efficiency of denitrifying biological filter（DNBF）.At present,the most widely used fillers include ceramsite and quartz sand,but most of these traditional fillers have low specific surface area and high specific gravity.In use,there are some problems such as low membrane hanging rate and high operation cost of the filter,high specific surface area,low specific gravity Easily available fillers are the key to improve the performance of fillers.Based on the analysis of the characteristics of rubber particles,taking rubber particles as filler,this paper explores the sewage purification efficiency of denitrifying biofilter under different working conditions,reveals the purification effect of the filter on different sewage,analyzes the structural characteristics of microbial community in the filter by high-throughput sequencing,and deeply studies the sewage purification mechanism of the filter.The results are as follows:（1）Rubber particles contain 16%～18%carbon black and a small amount of zinc oxide,alkane oil and sulfur.Carbon black has strong adsorption capacity and enhances the adsorption of filler;The results of elemental analysis show that in addition to 97%C,there are trace elements such as Ca,Zn and Fe in rubber particles,which may promote the growth of microorganisms.Compared with ceramsite filter material with the same particle size,the surface of rubber particles is coarser,with a specific surface area of 1.385 m~2/g（ceramsite filter material 0.441 m~2/g）,a low density of 1.07*10~3kg/m~3（ceramsite filter material 1.74*10~3kg/m3）and a bulk density of 0.533*10~3kg/m~3.These characteristics help to reduce operation energy consumption and promote membrane hanging.（2）The start-up of DNBF coating of rubber particles takes 5 days.After coating,the effluent TN is 5 mg/L～10 mg/L,and the denitrification rate is 88.2%～94.5%.Taking the simulated sewage with TN of about 82 mg/L and C/N=8.5 as the influent,the effluent TN of HRT6h and HRT 3H is 4.11 mg/L～8.44 mg/L,which is slightly higher than that of HRT 2H（2.84 mg/L～5.01 mg/L）;The effluent TN at hrt1.5h is similar to that at 2h,and the COD removal rate is slightly lower than 2H;In addition,longer HRT will cause effluent turbidity.2h HRT should be selected comprehensively.During operation,the filler layer floats up,and the floating phenomenon disappears after backwashing.The denitrification rate of the filter reaches 95.13%16 hours after backwashing,and the effluent TN is 4.03 mg/L.after40 hours,the effluent TN of the system is 2.5 mg/L,and the TN removal rate is97.01%,which is about 4%higher than that before backwashing.The filter is restarted after 6 days of shutdown,and the denitrification rate is 89.7%in 12h.After24h,the effluent quality tends to be stable,TN is about 5mg/L,and the denitrification rate is about 95%.（3）When rubber particle DNBF is used to treat the effluent from the secondary sedimentation tank of simulated printing and dyeing enterprises（COD 375 mg/L,TN 82 mg/L,TP 20 mg/L）,the effluent TN is lower than 6.5 mg/L,and the COD removal rate is 70.7%～81.3%;When treating simulated domestic sewage（COD 230mg/L,TN 40 mg/L,TP 6 mg/L）,the COD removal rate is 72.9%～79.6%,and the effluent TN is less than 3 mg/L.the filter has a good purification effect on COD and TN,and the TP removal rate is 60%～80%.The change of pollutant concentration along the way shows that the pollutant removal rate in the front and middle section of the filter is high,and the denitrification process is mainly concentrated in the front and middle section.（4）When treating the effluent from the secondary sedimentation tank of simulated printing and dyeing enterprises,the dominant bacteria in the filter are denitrifying functional bacteria,and desulfurizing bacteria are also relatively abundant.Most of the bacteria in the top 15 of the average abundance are common denitrifying bacteria,and the content is high in the middle section in front of the filter.There are several salt tolerant bacteria（alisewanella,paludibacter）and denitrifying phosphorus removal bacteria（Pseudomonas）in this section at the same time,so it can remove phosphorus pollutants while denitrifying significantly;The content of desulfurizing bacteria in the back section of the filter is high,which is related to the decrease of nitrate nitrogen concentration in the water and sulfate.The diversity of microorganisms in the front section is the highest and the rear section is the lowest,and the difference of microbial community in the rear section is the largest compared with the front and middle section. |
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