Study On Operation Of Groundwater Nitrogen Removal System Based On Solid-phase Denitrification

With the continuous development of society and economy,groundwater nitrate pollution is increasing,and there is a huge threat to the environment and human health.Solid-phase nitrification is a biotechnology for efficient and stable removal of groundwater nitrate.In this study,polycaprolactone?PCL?was used as a membrane carrier and a carbon source donor for microorganisms,A solid carbon source biofilm denitrification column system was established to remove nitrate in groundwater,and the filling rate and hydraulic retention time??HRT??of the reactor packing were analyzed on denitrification,to explore the optimal operating conditions for system operation,and the effect of Cu²⁺on the denitrification and adsorption of Cu²⁺in the reactor was investigated,and the copper metal tolerance of the denitrification column was understood.,and the effects of replacement rate and replacement method on the nitrogen removal performance recovery ability of the system were explored to determine a suitable replacement method,and a long-term operation test was performed to verify the feasibility of the replacement method.At last the experiment uses key enzyme activity detection and high-throughput sequencing to understand the microscopic changes of microbial denitrification,and provides important theoretical basis for groundwater nitrate repair technology.The main conclusions are as follows:?1?Filling rate and hydraulic retention time have a significant effect on the denitrification effect of the solid carbon source biofilm denitrification column.the carbon supply of a system with a filling rate of 40%is appropriate with the average NO₃^--N removal rate up to 94%,When the carbon source in the system is sufficient,the nitrogen load in the flooding water is increased,and the system can still be in full denitrification.when HRT was 4h,denitrification was complete and the by-product yield was small,the average NO₃^--N removal rate was 88%,and the average effluent TOC concentration was 20.51 mg/L.It can be seen that the filling rate is40%and the HRT is 4h,which meets the long-term high-efficiency and stable operation of the solid carbon source biofilm denitrification column,which is a suitable operating condition.?2?In the copper metal tolerance experiment,it was found that when the Cu²⁺concentration is low(?(Cu²⁺)?1.10mg/L),the copper metal denitrification column of the solid carbon source biofilm is highly efficient and stable,the average TN removal rate is higher than93%,and the average adsorption rate for Cu²⁺is greater than 85%.When the Cu²⁺concentration in the formulated water is higher than 4.67 mg/L,the denitrification of the denitrification column is significantly and reversibly inhibited,and the Cu²⁺adsorption is also affected.The denitrification and adsorption performance of the system deteriorates with increasing concentration.When the Cu²⁺concentration was 4.67mg/L and 11.00mg/L,the average TN removal rate in the system were 84.47%and 59.87%,and it can be restored to 89.70%and67.43%,and the adsorption rate changes 11.91%and 18.85%.?3?In the study of exploring the replacement method of the packing,it was found that the solid carbon source biofilm denitrification column had the best recovery performance when the replacement method was used to replace the 30%packing in the longitudinal direction.Reactor B#successfully operated for 200 days using this replacement method.Through the above experimental research,it is indicated that the solid carbon source biofilm denitrification column using polycaprolactone as a filler can efficiently and stably remove nitrate in groundwater.