Effect of Ca:Mg ratio and high ammoniacal nitrogen on characteristics of struvite precipitated from waste activated sludge digester effluent  

作　　者：Chathurani Moragaspitiya Jay Rajapakse Graeme J.Millar 

机构地区：[1]Science and Engineering Faculty, Queensland University of Technology (QUT)

出　　处：《Journal of Environmental Sciences》2019年第12期65-77,共13页环境科学学报（英文版）

基　　金：funded through the financial support of “Australian Government Research Training Program (RTP) Stipend”;supported by generous funding from the Science and Engineering Faculty (SEF-QUT)

摘　　要：This study revealed the relationship between the presence of calcium impurities and ammoniacal nitrogen concentration upon crystallization of struvite.The research hypothesis was that the presence of both calcium and high concentrations of ammoniacal nitrogen(328–1000 mg/L)in waste activated sludge may influence the struvite quality and acid stability.Hence,we studied the impact of Ca:Mg ratio upon morphology,particle size,purity and dissolution of struvite,in the presence of varying levels of excess ammoniacal nitrogen.X-ray diffraction revealed that up to 31.4%amorphous material was made which was assigned to hydroxyapatite.Increasing the ammoniacal nitrogen concentration and elevation of the Mg:Ca ratio maximized the presence of struvite.Struvite particle size was also increased by ammoniacal nitrogen as was twinning of the crystals.Tests with dilute solutions of organic acid revealed the sensitivity of struvite dissolution to the physical characteristics of the struvite.Smaller particles(21.2μm)dissolved at higher rates than larger particles(35.86μm).However,struvite dissolved rapidly as the p H was further reduced irrespective of the physical characteristics.Therefore,addition of struvite to low p H soils was not viewed as beneficial in terms of controlled nutrient release.Overall,this study revealed that waste activated sludge effluent with high ammoniacal nitrogen was prospective for synthesis of high quality struvite material.This study revealed the relationship between the presence of calcium impurities and ammoniacal nitrogen concentration upon crystallization of struvite. The research hypothesis was that the presence of both calcium and high concentrations of ammoniacal nitrogen(328–1000 mg/L) in waste activated sludge may influence the struvite quality and acid stability. Hence, we studied the impact of Ca:Mg ratio upon morphology, particle size, purity and dissolution of struvite, in the presence of varying levels of excess ammoniacal nitrogen. X-ray diffraction revealed that up to 31.4%amorphous material was made which was assigned to hydroxyapatite. Increasing the ammoniacal nitrogen concentration and elevation of the Mg:Ca ratio maximized the presence of struvite. Struvite particle size was also increased by ammoniacal nitrogen as was twinning of the crystals. Tests with dilute solutions of organic acid revealed the sensitivity of struvite dissolution to the physical characteristics of the struvite. Smaller particles(21.2 μm) dissolved at higher rates than larger particles(35.86 μm). However,struvite dissolved rapidly as the p H was further reduced irrespective of the physical characteristics. Therefore, addition of struvite to low p H soils was not viewed as beneficial in terms of controlled nutrient release. Overall, this study revealed that waste activated sludge effluent with high ammoniacal nitrogen was prospective for synthesis of high quality struvite material.

关 键 词：STRUVITE PURITY Calcium Ammoniacal nitrogen Waste activated sludge 

分 类 号：X70[环境科学与工程—环境工程]