A process for the treatment of phosphoric acid plant pond water
facilitating the recovery of phosphorus values from the input pond water.
In certain aspects the process recycles solids from a later stage
neutralization and separation into the clarified liquid stream from an
initial clarification and neutralization stage. A sufficient amount of
solids are added to the clarified liquid stream to effect the
pH-dependent precipitation of a phosphate product. In alternative aspects
an intermediate pH-dependent precipitation of a phosphate product is
achieved through the addition of a neutralizing agent. The phosphate
product is further characterized by a low concentration of fluoride. In
addition the phosphate product can be further processed to a high purity
technical grade phosphoric acid. In certain aspects the process employs
flocculating agents to enhance the formation of precipitates. In further
aspects, methodologies taught herein facilitate the reduction of silica
in the process streams. Processes according to the present invention are
further characterized by an enhanced recovery of treated water, reduced
sludge impoundment and reduced lime consumption when compared to
conventional double liming processes.