May 2006 - Environmental considerations along with economical benefits of the water reuse have triggered the interest of the industry to develop a new ZLD tech-nology for the treatment of liquid effluents.

GEA Messo GmbH developed a hybrid ZLD process for an 80 m³/h effluent from a Molybdenum production facility containing among others ammonium sulphate, sodium chloride, as well as magnesium and potassium sulphates. The hybrid process consists of a pretreatment section with brine purification, followed by a RO preconcentration and further concentration in a falling film MVR evaporator. A dedicated crystallizer and the solid separation complete this process, which, except for this solid waste only produces pure water for re-use in the production facility.

This development project was executed in close co-operation with the membrane department of GEA Wiegand GmbH. While existing technology is rather sensitive to incrustations, the present process is specifically designed to remove hardeners and fouling components in front of the concentrations units. The use of RO instead of evaporation allows a significant cost reduction and improves overall process economics.

In order to proof the new process, laboratory and pilot tests were carried out, initially at the GEA Messo laboratory and then later at the client’s site on a larger scale. Major focus was on the proper precipitation of the alkaline earth metal (Ca2+ and Mg2+) as this represents an essential precondition for the reliable use of the membrane and the evaporation process. Due to the selective removal of such alkaline earth metals the falling film evaporator could be operated in an un-seeded mode, thereby simplifying overall process complexity. Process design was proven by detailed test works and shows an excellent precipitation of Calcium and the other membrane endangering components, like e.g. colloidal SiO2, Mn and Fe.

With its experience in process development work, its existing laboratory facilities and its practical experience as a world wide plant constructor GEA Messo GmbH is the partner in developing your custom made Zero Liquid Discharge process for your specific waste water.