Study On The Removal Of Phosphate By Struvite Crystallization Combined With Zeolite Adsorption

Nowadays,most of the rivers and lakes in our country are in the state of eutrophiction.The reason that causes this phenomenon is mainly of the excessive emissions of nitrogen and phosphorus,so how to recovery of phosphorus from waste water catch many researchers' attention.As one of the most effective way to recovery of nitrogen and phosphorus currently,struvite is widely used in the practice.However,struvite crystallization method still have two problems: firstly,the addiction of magnesium source is too large and then the processing cost is too high.Secondly,the advance treatment effect of waste water is poor.In order to solve the above problems,an in-depth study of struvite crystallization method was implemented.The emvironmental results show that the optional reaction conditions of struvite crystallization are pH=9.5,n(Mg): n(N): n(P)=1.2:1.2:1,reaction time is 30 min.In this study,five pollutants was chosen to investigate their influences of crystallization reaction.Acetic have no influence on the struvite crystallization reaction,sodium alginate and bovine albumin has a slight effect on it,and the influence of F-and Zn2+ is significantly.Then,low-grade magnesium oxide and magnesium alloy are used as the source of magnesium.The result demonstrated that these two kinds of magnesium source can achieve in reaction equilibrium in a short time,and the removal rate of phosphorus were above 90%.Because the advanced removal effection of phosphorus in wastewater is poor,adsorption method is used to dispose the effluent secondary.In this experiment the phosphorus removal effection and adorption performance of Mg/Al-LDHs and zeolite were studied.The experimental results show that the rate of Mg/Al-LDHs adorption is quite quick.When the reaction time achieves 100 min,the adorption reaction reach the adorption equilibrium.The maximum adorption capacity can reach to 15mg/g.the zeolite adsorption rate is smaller than Mg/Al-LDHs and the maximum adorption capacity only can reach to 5.2mg/g.However,zeolite material is cheaper,bigger production and settlement.Comprehensive analysis,the use of zeolite adsorption combined with magnesium ammonium phosphate crystallization is more suitable for phosphorus removal process.