Gypsum scale reduction and collection from drainage water in solar concentration

Calcium sulfate scaling is a known issue with drainage water concentration systems. During preliminary pilot testing of a solar assisted agricultural drainage water salt concentration and recovery system, calcium sulfate dihydrate (gypsum) precipitated as a scale on the primary evaporator surface and on other water-side surfaces. The concentrator surface design may allow for recovery of gypsum as an additional product from the facility, in addition to the main product of sodium sulfate. Seeding with gypsum crystal was tested to reduce the scale growth and precipitate gypsum in suspension. The mechanical removal of gypsum from a flexible concentrator surface was also tested. As a result, the seeding process had influence on the scale formation and reduced calcium sulfate buildup on components of the evaporator system. (C) 2010 Elsevier B.V. All rights reserved.