Abstract:
Phosphorus (P) is an essential element for living creatures and is predicted to be depleted out within the next 100 year or so. New Zealand is in urgent need of P management and recovery as it can not only reduce the country‘s P rock import and fertilizer consumption, but also help minimize the environmental impact in the agricultural industry by improving the P resource utilization efficiency across the country. This project aims to identify the most suitable streams for economical P recovery via struvite crystallization in New Zealand. A global P depletion model was constructed and a P flow analysis was conducted to distinguish and quantify different P flows within New Zealand. Struvite crystallization in dairy wastewater was found to be an effective solution for P utilization efficiency improvement. To resolve the negative extent of the effect of calcium in the dairy wastewater, quantitative recommendations around where P recovery using struvite crystallization is feasible was established. At the same time, an empirical and a thermodynamic model were constructed to predict the struvite purity under various wastewater compositions. The developed models can be used to as a preliminary tool to check whether the desired product is attainable and if, and how much, magnesium can be used to compensate for low product quality.