Research On Low C/N Domestic Sewage Treatment By Potassium Ferrate+A/O-MBR Combined Process

Influenced by geography,climate,living habit,urban sewage has the following features: large displacement,ow concentration of organic matter,and low C/N ratio.However,the traditional activated sludge method to treat domestic sewage with low C/N ratio often has shortcomings such as low treatment efficiency,needing a large number of carbon sources,resulting in increased costs,and easy to lead to sludge expansion.In view of the low efficiency of traditional activated sludge treatment and the shortage of sludge swelling,this study takes hypoxia/aerobic membrane biotechnology(A/O-MBR)as the main process,and potassium ferrate cell dissolution to crack the remaining sludge as the branch process,combining the two to improve the domestic sewage treatment effect with low C/N ratio and realize sludge reduction.This project studied the effect of strong oxidation of potassium ferrate on sludge properties.Through experiments on the main influencing factors such as potassium ferrate concentration and reaction time,the liquid SCOD concentration of sludge mixture was used as the measurement index to obtain the appropriate reaction conditions for potassium ferrate cell dissolution.The research results show that when the concentration of potassium ferrate dosing is 0.1 g/g SS,the response time to 20 min,the dissolved cell cracking effect of potassium ferrate is best,less crack sludge sludge mixture liquid SCOD concentration increase by about 400%,rising nutrient concentration in the liquid phase to some extent,the ammonia nitrogen concentration increased from 1.88 mg/L to 13.51 mg/L,TN concentration rise by 11.91 mg/L to 48.60 mg/L,TP concentration increased from 1.12 mg/L to 18.43 mg/L.At this time,the sludge is loose,the specific surface area increases,and the contact area with sewage increases.At the same time,the sludge MLSS and MLVSS decrease significantly,realizing the sludge reduction.The combined potassium ferrate +A/O-MBR process was operated under the optimal sludge reaction condition.The results showed that the average removal rate of COD in the combined potassium ferrate +A/O-MBR process was 4.87% higher than that in the A/O-MBR process.The average removal rate of TN was 9.14% higher.The average removal rate of ammonia nitrogen was 1.53% higher.The removal rate of TP was 0.34% higher,and the combined process improved the treatment effect of domestic sewage with low C/N ratio.Compared with the A/O-MBR process,the combined process reduced sludge discharge by 7.9L,a total of 0.044 kg.The average MLSS of sludge decreased by 512mg/L,and the average MLVSS/MLSS decreased by 0.01%.Membrane fouling cycle is reduced by 2d.The Fe content in liquid and solid phases was determined.Compared with A/O-MBR process,the average Fe concentration in effluent of combined process increased by 0.0011mg/L,which had almost no effect on effluent quality.The average Fe concentration in aerobic pond sludge of the combined process was 14.4mg /kg higher than that of the control group,and the additional Fe accumulated was 0.864 mg in total.According to the Fe concentration in the effluent,the accumulation of Fe in sludge did not cause Fe pollution in effluent.The results of material balance analysis showed that the COD discharged from the combined process system was 7.67% of the inlet water,22.48% less than the control group,and the TN discharged was 39.14% of the inlet water,17.15% less than the control group,indicating that the combined process of potassium ferrate +A/O-MBR achieved sludge reduction and the pollutant removal rate increased.Studies on the denitrification mechanism of potassium ferrate +A/O-MBR showed that COD was more suitable than TOC to measure the change of carbon source in denitrification process.Compared with A/O-MBR,SMP and EPS increased by 8.36% and 9.69% respectively,which was conducive to the improvement of the denitrification effect of the combined process.The denitrification rate of the combined process was 64.70%,which was better than the A/O-MBR process 8.82%.However,due to the lack of carbon sources in the water with a low C/N ratio,the denitrification effect of the system wasn't good.The lack of inlet carbon source was still the main reason to limit the denitrification effect of the system.