Removal And Concentration Of Phosphate And Ammonia Ions In Water By Electrodeionization

Human activity increased the input of nitrogen and phosphros in natural water, which led to the high frequency of eutrophication. Nowadays, how to eliminate the ammonia and phosphate ions from water has become the research hotpots. The major technologies to remove the nitrogen and phosphorus include precipitation, crystallization, ion exchange and so on. All of these methods have the disadvantages of high cost and low removal efficiency. Meanwhile, nitrogen and phosphorus are the necessary elements of plants, showing the high value to be reused as resource. This paper used the electrodeionization (EDI) technology to remove and recovery the ammonia and phosphate ions simultaneously. On the one hand, the ammonia and phosphate ions were removed from the wastewater to meet the requirement of discharge. On the other hand, they were concentrated and resued.EDI is a new environmentally effective seperation technology, which was successfully applied in removal and recovery of heavy metal ion and preparation of ultrapure water. EDI combined both advantages of electrodialysis and ion exchange. This paper studied the treatment performances and rules of wastewater containing ammonia and phosphate.An EDI reactor containing five compartments has been designed and produced, including cycle and continuous operating process. Firstly, the materials and operating parameters was determined, to prove the feasibility of ammonia and phosphate removal and recovery. Then, the effects of applied voltage, influent phosphate concentration and influent flow rate on the EDI performances were explored. Two kinds of ion exchange resins (D001and D201) were mixed with a ratio of 1:1 and were saturated with phosphate in EDI system, The suitable applied voltage was 30 V, the suitable influent flow rate was 5 mL/min, and the suitable influent concentration was 100 mg/L. Under the suitable conditions, the effluent phosphate concentration of dilute compartment was 15.68 mg/L after 10 h continuous operation. The phosphate removal rate was 86.3%, the enrichment factor was 2.58 and the current efficiency was 56.6%. The results indicated that the EDI can remove and concentrate the phosphate continuously and effectively.In addition, the effects of applied voltage, influent phosphate concentration and influent flow rate on the EDI performances were analyzed. The applied voltage was determinant, which affected the ion migration by changing the electric driving force. The influent concentration impacted the ion migration by controlling the conductivity and resistance of EDI system. The influent flow rate impacted the ion migration by controlling the residence time of ions.Finally, the EDI performances of simultaneous removal and concentration of ammonia and phosphate ions were explored and analyzed, and the effects of applied voltage on the EDI performances were briefly studied. After 3-hour operation, the ammonia concentration on different voltages varied from 7.5 to 29.1 mg/L, the ammonia removal efficiency was 95.0%, and the enrichment factor varied from 0.82 to 1.36. The phosphate concentrations under different voltages varied from 9.1 to 30.6 mg/L, the phosphate removal efficiency reached to 94.5%, and the enrichment factor varied from 1.00 to 1.15. The results illustrated that the EDI can remove and concentrate the ammonia and phosphate ions simultaneously.