Impact of calcium on struvite crystal size, shape and purity

Abstract

Struvite precipitation occurs spontaneously in wastewater treatment plants under conditions that are influenced by many factors including concentration of PO ions, pH, temperature and mixing energy. These parameters are often difficult to control and as a result struvite generates problems of scale deposits in areas such as pipes and recirculation pumps. At the same time, struvite is considered as a potentially marketable product as an alternative fertiliser. For those two reasons, it has become important to study the principles of struvite precipitation, and to assess the parameters controlling struvite crystallisation. In the present work the influence of 2 effects of Ca 2+ ions on size, shape, and purity of the crystals formed. Tools used include particle size analysis, X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDS). The experimental results showed that the presence of calcium in the media can affect significantly struvite crystal growth, and the characteristics of the crystal produced.

Modeling and Optimization of Phosphate Recovery from Industrial Wastewater and Precipitation of Solid Fertilizer using Experimental Design Methodology

“…Calcium ions actively react with phosphate to form calcium phosphates. Previous studies on the influence of calcium on struvite crystallization reported that Calcium ions with struvite co-precipitation can retard the nucleation induction and inhibit the growth for struvite crystal formation 6,7 . However, calcium, as an impurity, could be a negative factor for struvite formation.…”

Effect of Calcium Additive on the Crystallization of Struvite

“…Calcium ions can actively react with phosphate to form calcium phosphates. Previous works on the effects of calcium on struvite crystallization reported that calcium ions with struvite co-precipitation may retard the nucleation induction and inhibit the growth of struvite crystal formation (Le Corre et al, 2005). Moreover, calcium, as an impurity, could be a negative factor of struvite formation.…”

“…As a consequence of obstruction for crystallisation of struvite, the change in the characteristics of struvite crystals may occur, however this area of research has not been examined in detail in terms of qualitative and quantitative. Thus only limited study has been conducted in this area of research (Le Corre et al, 2005). Here, an improved understanding on struvite precipitation out a solution due to the presence of ion additives is required.…”

Effect of organic matter on phosphorus recovery from sewage sludge subjected to microwave hybrid pretreatment

“…A possible explanation is that organic matter could bind to ions, thereby affecting ionic activity (Ronteltap et al, 2010;Udert et al, 2003). It was found that increasing the calcium concentration reduces crystal size and inhibits struvite growth, or affects struvite crystallization and leads to the formation of an amorphous substance rather than crystalline struvite (Le Corre et al, 2005). Lower MWt matters undergo complexation with calcium, and inhibit the competitive effect with Mg 2+ toward PO 4 3− .…”