| For the treatment of high-concentration NO3-in the sewage discharged by the nuclear fuel element company during the production process,denitrifying bacteria cultivation,simulated sewage treatment and actual sewage treatment were carried out.A bioreactor was used to conduct a flow reaction on simulated sewage and actual sewage,and single-factor experiments were conducted on the temperature,C/N?Carbon-to-Nitrogen ratio?,pH,NO3-concentration,and HRT?Hydraulic Residence Time?that affect the denitrification effect.the result shows:?1?The activated sludge in the anaerobic reaction tank of the sewage treatment plant was used as the strain to cultivate the denitrifying bacteria,and the change of NO3-concentration in the culture medium was analyzed.Through a single factor experiment,it was found that the denitrifying bacteria are mesophilic bacteria,and the suitable temperature is 25-35?;the bacteria have a good removal effect on NO3-with a concentration of250-1500 mg/L;the suitable pH of the denitrifying bacteria is neutral;The minimum C/N required for the denitrifying bacteria to reach a removal rate of over 90%is 1.5.?2?The simulated sewage is used for the hanging film and flow test of the reactor.In the stage of film hanging,with the increase of the number of film hanging,the time required for the effluent to reach the removal rate of more than 90%was gradually reduced from 48 h to 6 h.Then flow reaction was carried out,and the HRT at the beginning of the flow reaction was 6 h.The results show that the HRT required to achieve a 90%removal rate gradually decreases as the reaction proceeds.When the HRT is 2 h,the NO3-concentration of the effluent is 10 mg/L,the NO3-removal rate is 98%,and the nitrogen volume load is 0.613 kg·N/m3·d;when the HRT is 1.6,the NO3-concentration of the effluent is 55 mg/L,NO3-removal rate is 89%,and its nitrogen volume load is 0.696 kg·N/m3·d.?3?The down-flow fixed-bed bioreactor was used to perform NO3-removal test on the sewage discharged in the production process of a nuclear fuel element company.The NO3-concentration of the actual sewage is analyzed,and it is found that its NO3-concentration is greater than 30 g/L,which is much greater than the NO3-concentration of the simulated sewage,so the actual sewage is diluted with tap water to reduce the NO3-concentration to facilitate the removal experiment.The actual sewage with NO3-concentration of 1 g/L was used for adaptive cultivation and domestication of the bacteria,and the actual sewage with NO3-concentration of 2 g/L was used to hang the membrane and conduct flow reaction.The NO3-and NO2-concentrations of each sampling port of the reactor and the DO of the incoming and outgoing liquids were analyzed.The fixed conditions are C/N 1.5 and temperature 18-25?.When the NO3-concentration is 2 g/L,HRT gradually decreases from 8 h to 8 h,and the removal rate of NO3-is always greater than 98%without accumulation of NO2-;when the NO3-concentration is 4 g/L,HRT>0.8 h NO3-removal rate is always greater than 98%and no NO2-accumulation;when NO3-concentration is 6 g/L,HRT>1.1 h NO3-removal rate is always greater than 98%and no NO2-accumulation.When exploring the effect of C/N on the denitrification effect,the fixed NO3-concentration is 6 g/L and the temperature is 18-25?.As the C/N decreases from 1.5 to 1.1,the removal rate of NO3-is always greater than 98%without accumulation of NO2-,the time required for the reactor to reach 98%removal rate gradually increased;when C/N<1.1,the removal rate of NO3-began to decrease and there was accumulation of NO2-.In summary,the fixed-bed bioreactor has a good effect on the removal of high concentration NO3-in nuclear industrial wastewater.The bioreactor can maintain an efficient denitrification rate at>18?,and the bioreactor can achieve a removal rate of more than 95%under the condition of C/N1.1,which reduces the temperature requirement and reduces The consumption of carbon source provides a basis for the industrial removal of high concentration NO3-in nuclear industrial wastewater. |
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