The volume of water handled every day at a Florida Phosphate mine is greater than that of any other substance; including the phosphate. An average size mine is nearly always pumping several hundred thousand gallons per minute of water around the property. Prudent management of the water volume and its chemical composition is critical to the sustainability of this business; any failure to do so has the potential for consequences well beyond the property line of just that mine. Historically, management of the water has relied upon the human judgment of a few highly experienced individuals, and while they have done a very good job, the industry faces stricter effluent limitations in the near future. To ensure the mine is properly positioned to comply with these stricter limits and a desire to further improve water management decisions, a water model for one mine was created by Cardno for Mosaic utilizing the GoldSim modeling software. This pilot model was created to determine if the complexities of a typical phosphate mine can be successfully reduced to a mathematical simulation. The presentation will discuss how this model was created including all the parameters considered for inputs and outputs (ore mined, rainfall, evaporation, seepage, ground water use, beneficiation impacts, etc.). After completion of the project a validation of the model compared model predictions with actual results. Those results will be shared
The main objective of the model is to estimate the probability that the mine would need to discharge water from the mine and/or the nutrient levels would exceed regulation limits. The model takes into account the operations decision making at the various facilities and handling of materials and water. Initial results show the model accurately predicts discharge probabilities and levels by simulating the water management decisions throughout the mine. Secondary objectives are to predict pond water levels during varying hydrologic scenarios. These predictions could be valuable information to improve management decisions (what level to hold ponds at in preparation for rainy season and major storms). Past observations indicated an unknown process was removing phosphorous from the water system.
This project sought to investigate this phenomenon by:
- Confirming the removal process exists.
- Where in the mine does it occur?
- Quantify how effective it is at removing phosphorus.
- Speculate on the chemistry behind the removal process (biological, adsorption, precipitation).
Remaining work to be done on this project includes further development of the nutrient consumption model, which is used to predict future concentrations.
In conclusion, GoldSim has provided a robust framework to simulate this complex flow network, along with all the decision logic and dynamic changes that occur in an efficient manner. Cardno was able to better use their ranges of expertise to solve the problems of the application while GoldSim took care of the details needed to handle complex data, organize concepts into model logic, and develop coherent results that can be used by all the various stakeholders involved. For more information about this project, please see the Transcript of Mine Water Solutions in Extreme Environments, 2015.