Treatment of nitrogen and phosphorus from wastewaters by magnesia

Key words: 
• magnesia /
• nitrogen /
• phosphorus /
• removal /
• wastewater

Abstract: Removing nitrogen and phosphorus from simulated and actual wastewaters by magnesia was carried out. Some factors affecting the removal efficiency of nitrogen and phosphorus were discussed, including the dosage of magnesia, pH, and the reaction time. In addition, the dynamics of the process was studied as well. Meanwhile, the magnesia and the products of the process were analyzed by XRD. The results show that the optimal technological conditions for the removal of nitrogen and phosphorus from wastewater (200 mg/L nitrogen) were: mass ratio of magnesia and nitrogen of 25∶1; balance time of 10 min, the removal rate of ammonia nitrogen and phosphorus reached to 93% and 99%,respectively. For the actual wastewater (590 mg/L ammonia and nitrogen, 1 630 mg/L phosphorus) in Nanjing, the removal rate of ammonia nitrogen and phosphorus reached to 92% and 99%,respectively. The dynamic data could be described by the pseudo secondorder model, implying a chemical reaction. The XRD analysis indicates that the major component of the precipitation is NH4MgPO4, which demonstrates further a chemical reaction.