Access to safe and high-quality drinking water is essential for a functioning society, particularly on Öland where seasonal water demand is high. Borgholm Energi AB produces drinking water through seawater desalination using reverse osmosis. The resulting water is highly demineralized and requires remineralization to meet drinking water standards. 

Currently, the imported filter material Hydro Calcit is used for this process. Although it performs well, it involves transport-related environmental impacts and costs. This study investigates whether locally sourced limestone from Öland can replace Hydro Calcit as a remineralization material to support a more sustainable water supply.

Two types of limestone from Öland were calcined and hydrated under laboratory conditions and used to remineralize deionized water. The resulting water was analyzed with respect to calcium, magnesium, and other relevant mineral concentrations, as well as potential release of unwanted substances. The physical properties and functionality of the materials were also assessed. 

The results were evaluated against Swedish drinking water regulations to assess suitability for full-scale application. The analyses show that both types of limestone influence the chemical composition of deionized water by increasing calcium, alkalinity, hardness, and conductivity. Compared with Hydro Calcit, the Öland limestone resulted in less controlled water quality, highlighting the need for further optimization before potential full-scale implementation.

Keywords: deionized water, remineralization, remineralization material, limestone from Öland, Hydro Calcit, drinking water quality, reverse osmosis, sustainable water supply