| As an effective water treatment technology,coagulation was often used in conjunction with other water treatment processes such as catalytic oxidation,membrane separation and biological treatment due to its high flexibility.Among them,the pre-coagulation + biological treatment system can effectively improved the efficiency of urban sewage purification.Through the enhanced pre-coagulation of the sewage,the water quality can be adjusted and the refractory organic matter can be separated,so as to shorten the aeration time,improve the denitrification efficiency,reduce the volume of sewage treatment facilities,and save the construction cost.In this paper,copper ions were introduced into polyferric sulphate(PFS)by blending modification to prepare polyferric copper sulphate(PFCS)to strengthen a pre-coagulated biological treatment system: compacted preseparation biological treatment(CPSBT)system.The particulate and colloidal pollutants in the sewage were separated by coagulation pretreatment,which played a role in regulating water quality;the influence of copper on microbial activity was used to inhibit the release of pollutants in the sludge produced by coagulation.At the same time,it promoted the efficiency of subsequent biological denitrification and achieved the purpose of strengthening the precoagulation biological treatment system.First of all,under the PFS/PFCS system,using scanning electron microscope(SEM)to observe the surface morphology and structure changes of the coagulant,the results showed that the structure of the PFS and PFCS were different.At the same time,using X-ray diffraction(XRD)analysis method,it was shown that a series of chemical reactions in PFCS lead to the appearance of new diffraction structures.Secondly,the coagulation effects of PFS/PFCS under different dosages were studied.The results showed that PFCS has good coagulation effect on particulate matter.The turbidity removal effect reached was more than 92%,and the removal rate of TN was about 31%.The comparison of the removal rates of TP,TN,COD and DON showed that the coagulation effects of PFCS and PFS were similar.The removal rate of COD was over 40%,and the removal rate of TP was as high as 97%.The removal efficiency of coagulation for dissolved substances was low,and the removal rate of DON was about 20%;after detecting the residual copper concentration in the water after sinking.It was found that with the increase of the copper-to-iron ratio at the same dose,the copper concentration in the water after sinking would also be increased.when the copper-to-iron ratio was 1/50,the residual copper concentration was low,and the effluent was less than 0.5 mg/L when the dosage was high,which meet the "Discharge standard of pollutants for municipal wastewater treatment plant".In order to investigate the impact of coagulation on the overlying water,under the PFS/PFCS system,the investigation was carried out from two perspectives: the number of microorganisms in the sludge and the change of pollutant concentration in the overlying water.The sludge produced by PFS was the control group.The results showed that the number of microorganisms in the PFS sludge was lower than 25% of the control group,and the concentration of COD,ammonia nitrogen and nitrate nitrogen were about 50%,25% and 25%,effectively,of the control group.Which inhibited the release of sludge and strengthen the coagulation effect.Finally,the raw water as well as the supernatant of PFS and PFCS were denitrified in the SBR.The aerobic stage,anaerobic stage and effluent quality were studied separately.The effects of using PFS and PFCS in CPSBT system were also detected.The results proved that under the influence of copper,the rate and effect of biological denitrification can be promoted.The average denitrification rate of the SBR was more than 90%,and no negative effects caused by copper due to cyclic operation... |
PDF Full Text Request