Phosphate plant pond water or process water can pose significant environmental risks and economic liabilities. Double liming has been the traditional treatment method for remediation of pond water. However, double liming suffers from several disadvantages, not the least of which are that the treated water often barely meets discharge criteria and that post-treatment air stripping is often required to attain acceptable ammonia concentrations. Reverse osmosis (R.O.) has long been viewed as an attractive alternative for pond water remediation. However, to be successful, the use of R.O. in the processing of pond water requires some form of pretreatment.
In 2001, IMC developed an R.O. pretreatment process in anticipation of having to treat and discharge water from their Uncle Sam, Louisiana, plant. While water discharge at the Uncle Sam plant was ultimately not needed, the situation at Piney Point provided a unique opportunity to prove the process at a large scale, while aiding the State of Florida in closing the Piney Point gypsum stack.
In early 2004 a large-scale plant, using IMC technology, was built at Piney Point, operated for 4½ months and produced approximately 46 million gallons of high quality water for discharge. Several process improvements were tested and implemented and real-world process economics determined.
Kenneth J. Jardine, William N. Futch, and Dennis H. Michalski, The Mosaic Co.; Vaughn V. Astley, Dr. Phosphate, Inc. November 2005.