Towards a water-wise world Annual report 2014

Sara Salvador Cob doctorate 

Reducing residual streams in drinking water production

3 June 2014Research

Nanofiltration (NF) and reverse osmosis (RO) membranes are used to produce clean water. But besides producing clean water the process also produces a concentrate, which contains most of the impurities. Strict regulations govern the discharge of this concentrate into surface waters. At the same time, the water companies want to recover the valuable substances contained in the concentrate. Within the framework of her TU Delft doctoral work, Sara Salvador Cob conducts research at KWR into Zero Liquid Discharge (ZLD), a concept whereby the volume of the concentrate is significantly reduced.

Pilotinstallatie van Sara Salvador Cob

Pilot installation

Salvador Cob’s doctoral research is connected to the broader research conducted by KWR – among others, within TKI Water Technology – into smart ways of making ZLD possible in water desalination. The researcher focused specifically on a system consisting of cation exchange pre-treatment, followed by NF and RO. She studied the possibility of achieving a very high recovery – that is, a very low volume of concentrate.

Using the right combination of techniques, it is technically possible to approach ZLD. The system she studied could be applied in the production of drinking water from groundwater and surface water containing high concentrations of bivalent cations, silica and/or organic micropollutants. Water companies could adapt their processes based on these results. This would be especially interesting in areas where the discharge of concentrate streams is problematic or in those where water scarcity occurs.

Sara Salvador Cob

Sara Salvador Cob


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Scientific publications
Silica removal to prevent silica scaling in reverse osmosis membranes

Three strategies to treat reverse osmosis brine and cation exchange spent regenerate to increase system recovery