A major operating problem that has occurred in recycle flush lagoon systems is the buildup of a crystalline solid in the recycle pipelines, pump, flush devices, and concrete gutters. The major crystalline solid has been identified as magnesium ammonium phosphate -- Mg(NH4)PO4. There have been a couple of reports of other types of phosphate salts of calcium and magnesium. All the cases of salt buildup in the recycle lines of swine flushing systems that have been investigated in Kentucky were found to be magnesium ammonium phosphate.
Taraba, Joseph L., "Salt Buildup in Flush Recycle Systems" (1982). Agricultural Engineering Extension Updates. 56.