Fouling abatement in seawater desalination

Dissolved air flotation (DAF) in combination with ultrafiltration (UF) is gaining attention as a promising pre-treatment to reduce biofouling in SWRO membrane systems, particularly during algal blooms. The operation of DAF is always preceded by coagulant dosing (ferric chloride) to remove algae, organic matter as well as dissolved phosphate. Phosphates are known to form strongly bonded complexes with iron in the wide range of pH (Belelli et al., 2014, Tejedor-Tejedor et al., 1990). The application of UF downstream of DAF further enhances removal of small flocs that pass through DAF systems.
Despite advances in pre-treatment, biofouling in seawater reverse osmosis is still a major problem as neither DAF nor UF are optimized to remove dissolved phosphate or other nutrients. The potential sources of biodegradable compounds such as carbon and phosphate in seawater are: the raw water (presence of algae), chlorination of the raw water, and contamination of chemicals used in desalination plants. In this study, we will develop a method to measure low levels of ortho-phosphate in RO feed water for seawater & freshwater (<0.3 μg PO4-P /L). Then, the research will demonstrate and optimize the possible role of DAF and UF (with coagulation) in removing phosphate and other nutrients and reducing bacterial regrowth potential (BRP) in SWRO systems.
The research objectives are the following:
i) Develop a method that can detect low levels of ortho-phosphate (target ≤ 0.2 ppb) in freshwater and seawater;
ii) Optimize DAF and UF systems in reducing ortho-phosphate and bacterial regrowth potential prior to SWRO membranes systems;
iii) Quantify the role of chemicals used in SWRO in enhancing bacterial regrowth in desalination plants;
This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 606838, with additional support from IHE Delft.

Duration: 2 years
Post-doc: Dr. Mamoun Althuluth