Treatment of brackish groundwater - Executive Summary - Application of reverse osmosis in combination with freeze crystallisation can provide Vitens with the desired zero liquid discharge drinking water production and high-quality residuals

Based on the National Raw Materials Agreement, Vitens wishes to treat its raw materials – in this case, (brackish) groundwater – more economically and intelligently. Further research and development of the application of (eutectic) freeze crystallisation treating the reject stream produced by reverse osmosis [closed circuit reverse osmosis (CCRO) or ion exchange reverse osmosis (IERO)], can provide Vitens with the desired zero liquid discharge drinking water production, with a portion of the generated residuals being of high quality. This is the outcome of research based on literature and on expert findings, which involved the study of thirteen techniques. Total concepts were developed on this basis. Three other techniques [multi-stage flash (MSF), multi-effect distillation (MED) and supercritical water desalination (SCWD)] actually have the capacity of removing four critical substances (ammonium, chloride, iron and methane) in a single step, but they generate liquid and/or gaseous residual streams, rendering them unsuitable for drinking water production with zero liquid discharge.

Interest: produce drinking water with only high- quality residuals Based on the National Raw Materials Agreement, Vitens also wishes to treat its raw materials – in this case, (brackish) groundwater – more economically and intelligently. Drinking water production (for the most part) from fresh groundwater for 5.6 million Vitens customers generates a residual stream containing minerals and salts which are currently not (re)used. Vitens is therefore looking for (drinking) water production techniques that generate only high-quality residuals, so that the these can be usefully applied. Accordingly, Vitens requested a screening of water treatment techniques for possibilities for zero liquid discharge treatment of brackish groundwater producing water of drinking water quality. Vitens would like to be able to apply this (combination of) technique(s) location- independently, especially considering location- specific discharge requirements.

Approach: literature study and expert assessments Based on a screening of the SCOPUS database and inputs from KWR experts, a list was compiled of thirteen techniques that can be applied for the desalination of brackish groundwater. These desalination techniques are briefly described, as are their applications in the treatment of brackish groundwater referenced in the literature. The techniques were then assessed for their capability of removing four critical components from the brackish water: ammonium, chloride, iron and methane. These substances were selected based on the water-quality data provided by Vitens for brackish groundwater from the 1965_01 recovery well at the Ceintuurbaan pumping station. In addition, for each desalination technique, an assessment was made of the quality of the residual stream and of its phase (solid, liquid, gas).

Report: This tailored research for Vitens is described in the report Behandeling van brak grondwater (BTO- 2018.064).