Research On Enhanced Phosphorus Removal With Magnetic Loading Technology And Reuse Of Magnetic Particals

The Pure-MBBR process has limited phosphorus removal capacity,and as a biofilm water treatment method,the effluent contains aging and falling biofilm flocs.The floc structure is loose and the sedimentation performance is poor,and the conventional precipitation process is difficult to effectively remove.In this paper,the problem of phosphorus removal in the effluent of the PureMBBR process under low temperature conditions and the shedding biofilm flocs with poor sedimentation performance in the effluent were studied.The operating parameters of the magnetic loading coagulation and dephosphorization technology were applied to the phosphorus removal effect and sludge.The influence of sedimentation performance and the research on magnetic recovery technology were carried out.Conventional coagulation and phosphorus removal experiments under normal temperature and low temperature conditions were carried out with Fe Cl3,Fe2(SO4)3 and PFS as coagulants,respectively.The results showed that the Fe Cl3 had the best phosphorus removal performance among the three coagulants.The initial p H was 7?8,and the total phosphorus removal rate at normal temperature reached 96.14% under the condition of 90mg/L.The total phosphorus removal rate was 94.68%.The comprehensive performance of the three phosphorus removal coagulants was quantitatively evaluated by applying the analytic hierarchy process.The results show that the comprehensive performance of Fe Cl3 is optimal.Through the extensive range of coagulation and phosphorus removal experiments of Fe Cl3,the effect of Fe Cl3 as a coagulant on phosphorus removal under normal temperature and low temperature conditions was verified,and the dosage of coagulant in the subsequent magnetic loading experiment was determined to be 90 mg/L.The results of the magnetic loading coagulation experiment show that the addition of 500 mesh and 800 mesh magnetic species can improve the phosphorus removal effect of Fe Cl3 under low temperature conditions.Under low temperature conditions,the particle size of the loaded magnetic species is 500 mesh,and when the dosage is 70 mg/L,the total phosphorus removal rate of Fe Cl3 can reach 95.78%.The addition of 350 mesh magnetic species has little effect on the chemical phosphorus removal effect under low temperature conditions.The experimental results of the influence of the stirring condition in the flocculation stage on the magnetic loading and coagulation dephosphorization show that under the normal temperature condition,the optimal stirring speed of the 350 mesh magnetic species is about 60r/min,and the optimal stirring time is about 8min;500 The optimum stirring speed of the magnetic species is about 60r/min,and the optimum stirring time is about 10min;the optimum stirring speed of the 800 mesh magnetic species is 50r/min,and the stirring time is about 10 min.Under low temperature conditions,the optimum stirring speed and optimum stirring time of each magnetic particle diameter increased by about 18% and 24%.The results of magnetic loading on the sedimentation performance of sludge show that the two-dimensional fractal dimension of the dephosphorized sludge flocs produced by the loading of 350 mesh,500 mesh and 800 mesh magnetic species at normal temperature is 1.488,1.585 and 1.643;Under low temperature conditions,the two-dimensional fractal dimension of flocs generated after loading of 350 mesh,500 mesh,and 800 mesh magnetic species is 1.500,1.553,and 1.571,respectively.It is known from the experimental results that the addition of magnetic species can change the phosphorus removal.The compactness of the sludge flocs improves the sedimentation performance of the dephosphorization sludge.In this paper,a temperature-responsive effluent total phosphorus prediction model is constructed.Compared with the conventional prediction model,the temperatureresponsive total phosphorus prediction model is more robust,and the accuracy on the test data set is better than the conventional prediction model.The dosage of the drug in the magnetic loading coagulation process under low temperature conditions is controlled.The magnetic recovery section studied the effects of three kinds of magnetic stripping methods,namely hydraulic shearing,ultrasonic separation and aeration shearing,on magnetic recovery.The experimental analysis showed that the hydraulic shear magnetic stripping method is more suitable for engineering applications.