project

Pure Fresh Water and Salt

Changing conditions and future challenges such as anthropogenic pollution and salinisation mean that water utilities are faced with the task of improving robustness and their operational strategies. Reverse osmosis (RO) membrane filtration serves as a strong barrier for salts, emerging substances and pathogens. The resulting residual stream contains all these components in concentrated form, making the reuse or discharge of this concentrate stream difficult.

Technology

Current RO applications for freshwater sources generally have limited yields (typically 75-80%) because of the presence of organic components (both natural material and micropollutants) and inorganic components (such as Ca, Mg, SO4, HCO3, …) in the feed water. The pre-treatment of the fresh water by separating salt (nanofiltration) in combination with the exchange of salt (ion exchange) could result in a cleaner residual stream with a smaller volume and reduced concentrations of organic contaminants (including microcontaminants). Potentially, this could make the applicability of RO less location-dependent, and increase the amount of clean water produced, thereby improving the efficient use of fresh water.

Challenge

This study is developing innovative pre-treatment for RO that allows for:

  1. the primary separation of organic components (both natural material and micropollutants) and inorganic components from a freshwater source using double nanofiltration and, if necessary, supplementary liquid-liquid extraction;
  2. the simplification of the contents of the inorganic main stream with ion exchange to enhance the freshwater yield of RO;
  3. salts from the freshwater source to be recovered with innovative regeneration methods for saturated ion exchange resins for internal and/or external use/reuse.

Solution

A lab-scale proof-of-principle test will be used to determine the technological and economic feasibility of the innovative pre-treatment for RO using water taken from the field. This innovation is highly relevant at drinking water production sites where the challenges include freshwater availability, emerging substances, stricter discharge standards and/or salinisation.