Removal Of Phosphorus From Domestic Sewage Based On Electrochemical Technology

Phosphorus is one of the most characteristic emissions from the perspective of water eutrophication.It has the dual characteristics of pollution and resources.The efficient removal and recovery of phosphorus has become the focus of international attention.Overcoming the deficiencies of the traditional process,phosphorus removal from domesitc sewage and phosphorus recovery from urine obtained from source separation technology were studied based on green as well as highly controllable electrochemical technology.The main research contents and conclusions are as follows:Double aluminum anodes were used in phosphorus removal from domestic sewage in a unipolar parallel mode.The relevant factors of phosphorus removal by electrocoagulation were investigated.The relevant treatment process was optimized with the combination of response surface center composite design methods.The kinetics during the dephosphorization process,the isothermal adsorption behavior,and the physical properties of the flocculated products were systematically studied.The results show that the electrocoagulation technology has a good effect on the phosphorus removal from domestic sewage.The optimal conditions of response surface method are:p H=5.09,current density=12.40 A/m²,initial phosphorus concentration=10.18 mg/L,time=17.23 min,and the predicted maximum removal efficiency of phosphorus from sewage is99.69%.The removal process of phosphorus is in accordance with first-order kinetics and Langmuir adsorption model.In neutral or weakly alkaline sewage,the removal mechanism of phosphate was mainly adsorption and complexation,and the phosphate was finally converted into a combination of H₂PO₄^-or HPO₄^2-and aluminum hydroxy hydrolytic product.In addition,the effect of electrocoagulation and chemical coagulation was compared on the removal of total phosphorus in actual domestic sewage.The relevant results show that the in-situ aluminum hydroxy hydrolytic produced by electrocoagulation is more conducive to the removal of phosphorus in sewage,as well as less sewage sludge and lower energy consumption.Urine is one of the main sources for nitrogen and phosphorus in domestic sewage.Urine obtained by source separation method was treated by electrochemical technology.In static experiments,the relevant effects on the recovery efficiency of phosphorus,struvite morphology and purity were investigated including current density,initial p H,dilution factor and other factors.The results show that the initial p H had a greater effect on the recovery of phosphorus,meanwhile the current density and p H have a certain effect on the size of the precipitate.The purity of struvite crystals decreased with the increase of current density,initial p H and dilution factor.In continuous flow experiments,the current density was 20 A/m²,the initial p H was 9,and the optimal hydraulic retention time（HRT）was 3 h,100%recovery of phosphorus and struvite with the purity of up to 90%could obtained during urine processing.This method is available in practical value for terminal phosphorus removal,as well as in alleviating the shortage of phosphorus resources within a certain range.In short,the electrochemical technology has a bright future in the removal and utilization of phosphate from domestic sewage.