Phosphorus is one of the most important components of fertilizer and is a limiting resource for agriculture. Although high concentrations of phosphorus are found in dairy waste, the majority is not recovered.  One potential way to recycle phosphorus from dairy waste is through the formation of solid struvite, which contains an equivalents amount of ammonium, magnesium and phosphorus and can be used as a valuable slow release fertilizer.  However, a number of studies have shown that forming struvite from dairy waste is inefficient because of calcium competition during formation, high-suspended solid concentrations, and high ionic strength of the manure. Although several inhibitory effects of inorganic substance to struvite crystallization have been documented, few studies have been conducted to show that biomolecules, like cellulose and xylan, interferes with struvite crystallization. Cellulose and xylan are the most abundant organic matter in dairy waste and their interaction with the inorganic ions could result in poor struvite precipitation. Therefore, the objective of this study is to estimate the inhibitory effect of cellulose and xylan on struvite precipitation as a function of organic matter concentrations, pH, and Mg to P ratio. Preliminary results show that cellulose and xylan have different effects on the formation of struvite. For instance, the removal amount of NH<sub>4</sub><sup>+</sup> from the liquid phase was reduced by xylan concentration but not cellulose concentration. In contrast, an opposite trend occurred for the removal of P with cellulose and xylan when Mg was not sufficiently supplied. Characterization of the struvite and cellulose or xylan interactions by comparing the amount and size of crystalized struvite is ongoing.

Effect of organic matter on phosphorus recovery in dairy waste

251st National Meeting (2016)

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