Data fusion to monitor remineralisation of desalinated groundwater in calcite contactors

The emergence of organic micropollutants in surface waters and even groundwater and increasing salination in river delta areas, drives water utility managers towards adoption and application of advanced and robust barriers in drinking water production like reverse osmosis (RO) filtration. However, water produced by RO, called permeate, contains hardly any minerals, is corrosive and bitter in taste. Hence, remineralisation is needed to improve the permeate water quality and comply with (Dutch) drinking water regulation. In order to test the performance of remineralisation using limestone (calcite) filtration, a pilot-scale filter has been set up and connected to an RO filtration system that treats anaerobic groundwater and equipped with on-line sensors for pH, conductivity and carbon dioxide. The degree of (re)mineralisation was tested at different flow rates, a smaller calcite grain size and with a lower temperature than previous studies. The pilot shows that the degree of remineralisation performance can be monitored on the basis of a few on-line sensors and a model that describes the dissolution of calcite.