Study On Preparation Of PSAZ Coagulant And Removal Of Phosphorus In The Effluent Of Secondary Treatment

In recent years,the eutrophication of water body has attracted much attention.The deterioration of the water quality that it causes seriously affects people’s production and life.At present,there are two major categories of phosphorus removal technology at home and abroad,including biological and chemical methods.Biological phosphorus removal stability is poor.Biological method of phosphorus removal is easily affected by water quality and process parameters,and phosphorus removal efficiency is generally low.The traditional process of activated sludge denitrogenation and phosphorus removal can reduce the quality of the effluent TP to 1～2 mg/L,and it is difficult to reach the level of the promulgation of the new national emission standards(≤0.5mg/L).Moreover,there is a contradiction between sludge age and carbon source in the process of simultaneous removal of nitrogen and phosphorus from sewage,the two usually can not give consideration to the situation of poor phosphorus removal efficiency when the effect of denitrification is good in the actual application process.In view of the main problems existing in the wastewater biological phosphorus removal process,chemical phosphorus removal has become the first choice unit technology in the treatment project of phosphorus wastewater.Coagulation sedimentation is a reliable method for treatment of phosphorus containing wastewater.It has the advantages of stable and reliable performance.Choosing the right coagulant to enhance coagulation and sedimentation is the key to the treatment of phosphorus containing wastewater by coagulation sedimentation.Article first introduced the preparation of a new type of coagulant.Polysilicate aluminum salt is a composite polymer coagulant of polysilicate aluminum and aluminum salt based on polysilicate and aluminum salt coagulants,which have adsorption bridge and electric neutralization.The addition of zinc ions can change the structure of coagulant,so that polysilicate aluminum silicate coagulant has better net chain structure,and the effect of coagulating phosphorus removal is better.Prepare coagulant on the basis of polysilicic acid.This study used the orthogonal experimental method,in the level and the extreme data processing method to find the best combination of the effects of preparation factors,so as to determine the conditions of preparing PSAZ optimal system:room temperature 15-25 ℃;pH value is about 3;the concentration of sodium silicate is 0.3mol/L;n(Al+Zn)/n(Si)=1:1;n(Al)/n(Zn)=2:1;silicic acid activation time is 2h.The interaction between aluminum ions,zinc ions and polysilicic acid in PSAZ was analyzed by analysis of x ray diffraction and analysis of infrared spectrum.The results show that the aluminum salt,zinc salt and polysilicic acid have a certain chemical effect,forming an amorphous polymer.Scanning electron microscopy analysis of the morphology and structure of PSAZ showed that the surface of PSAZ aggregates showed compact lamellar aggregation morphology,indicating that PSAZ polymers had close molecular structure and generated chain network structure,which is very conducive to the improvement of coagulation effect.Removal of phosphorus in the effluent of secondary treatment by poly-silicate-aluminum-zinc coagulant(PSAZ)coagulant under different influence conditions was investigated.It was studied by single factor experiment,such as coagulant dosage,pH value,mixing time,mixing speed,reaction time,reaction speed and precipitation time of these factors.The influence rule of each factor is obtained,and then three influence conditions with significant influence are determined by Plackett-Burman design.The optimal combination conditions are determined by the steepest climbing method and the BBD response surface method through two multiple regression fitting and response surface analysis.At pH is 6.34,the rate of phosphorus removal is the best when the reaction time is 25.86 min and the precipitation time is 31 min.Finally,the accuracy of the optimal conditions determined by the model was verified by supplementary experiments.Compared with polymeric aluminum chloride(PAC),the effect of phosphorus removal was better than that of traditional coagulants.