Modeling and optimization of struvite precipitation process for phosphorus recovery from wastewater

The recovery of phosphorus from wastewater following struvite precipitation pathway can provide a viable and sustainable source for phosphorus. This pathway is important because current phosphorus ore reserves are expected to be exhausted within the next few decades, or, the recovery from the ores will become more costly. However, the recovery of phosphorus from wastewater is not straightforward due to the complexities arising from the number of variables and chemistry involved with the precipitation of phosphorus as struvite. Modeling the dynamic nature of the crystallization phenomenon appears to be the method of choice to control the process. In this study, a dynamic control model for phosphorus recovery process via struvite crystallization was developed. This model incorporated both chemistry and control software, and was used to increase the efficiency and ease of process operation of a pilot-scale fluidized crystallizer. This process model was the basis of an automatic controller that had the capability to manipulate flows and chemical additions, and thereby control the system at a desired set point. The control model was then used as a prediction tool to determine conditions that influence the supersaturation ratio — the primary control parameter — of the process.