Mohaned Sousi of Palestine earns Doctoral degree for research on drinking water treatment

Mohaned Sousi presented and successfully defended his PhD thesis and was awarded with a Doctoral degree on 9 December 2021. Professor Maria Kennedy and Professor Walter van der Meer were his promotors and Dr. Sergio Salinas-Rodriguez his co-promotor.

Download the thesis here

Water supply utilities aim at providing biologically safe and stable drinking water that does not support extensive bacterial growth during distribution, to prevent health-related risks and operational problems.

In the Netherlands, where no disinfectant residual is applied, multi-barrier water treatment strategies are followed to control bacterial growth. Therefore, membrane filtration, such as reverse osmosis (RO), is considered to achieve this aim, where considerable removal of bacterial growth-promoting nutrients has been reported. However, remineralisation of RO permeate is required to add the essential minerals for human consumption, like calcium and magnesium.

The focus of this thesis was (i) further developing the existing method to measure bacterial growth potential (BGP) to be applicable for ultra-low nutrient water such as RO permeate, taking into consideration the sensitivity of such water to external contamination during test procedures, and (ii) applying the developed method in a current water treatment plant, which showed that the bacterial growth in drinking water could be reduced by >75% after applying RO filtration compared with the existing conventional treatment technologies. This was attributed to the significant reduction in nutrients such as carbon and phosphate (>99%) with RO filtration.

The results showed that remineralisation adversely affect the RO permeate quality.