Phosphorus Management and Recovery via Struvite Crystallization in New Zealand

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.