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Assessing Pretreatment Effectiveness for Particulate, Organic and Biological Fouling in a Full-Scale SWRO
Almotasembellah Abushaban1,2,3, Sergio G Salinas-Rodriguez2, Delia Pastorelli4
1Water Management Department, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, 2628 CN Delft, The Netherlands.
Membranes
|March 6, 2021
Summary
Dual media filtration effectively removes particulate fouling in seawater desalination pretreatment. However, chlorination limits biological fouling removal, suggesting chlorine neutralization before filtration improves performance and reduces biofouling potential.
Area of Science:
- Environmental Science
- Water Treatment Engineering
- Desalination Technology
Background:
- Seawater reverse osmosis (SWRO) desalination requires effective pretreatment to prevent fouling.
- Dual media filtration (DMF) is a common pretreatment method, but its efficiency against organic and biological fouling is debated.
- Frequent chlorination in pretreatment can inhibit beneficial microbial activity within filtration systems.
Purpose of the Study:
- To investigate the removal of particulate, organic, and biological fouling potential using two-stage DMF in SWRO pretreatment.
- To compare the efficacy of DMF pretreatment versus DAF-DMF pretreatment in mitigating fouling.
- To assess the impact of chlorination on biological fouling potential within DMF systems.
Main Methods:
- Monitoring silt density index (SDI), modified fouling index (MFI), bacterial growth potential (BGP), organic fractions, and microbial adenosine triphosphate (ATP).
- Comparing fouling potential removal in DMF pretreatment versus DAF-DMF pretreatment configurations at full-scale SWRO plants.
- Analyzing the effects of weekly chlorination on biological activity and fouling potential.
Main Results:
- Two-stage DMF achieved high removal of particulate fouling potential (SDI15 >80%, MFI0.45 = 94%) and microbial ATP (>95%).
- Biological/organic fouling potential removal was limited (24-41%) due to weekly chlorination, which suppressed biological activity.
- DAF-DMF pretreatment enhanced biological/organic fouling removal, increasing BGP removal by 40% and biopolymer removal by 16% compared to DMF alone.
Conclusions:
- Neutralizing chlorine *before* media filtration is recommended over post-filtration chlorination to enhance biological degradation and reduce biofouling.
- Monitoring ATP and BGP in DMF pretreatment is crucial for optimizing biological degradation and minimizing SWRO feed water biofouling.
- Integrating dissolved air flotation (DAF) upstream of DMF significantly improves the removal of biological and organic fouling potentials.
