Low-Pressure Membrane Pretreatment by Dissolved Air Flotation: Comparison with Alternative Coagulation Strategies

Low-Pressure Membrane Pretreatment by Dissolved Air Flotation: Comparison with Alternative Coagulation Strategies Joseph D. High Organics/Colored Low Pressure Membrane Algal Impacted Waters Waters (LPM) Fouling The Need for Membrane Feed Water Pretreatment The effects of climate change are leading to natural waters with increased:  Frequency and intensity of algal blooms.  Color and dissolved organic carbon (DOC) content. Concepts 1 2 3 Keyword Dissolved Air Membrane Drinking Water Fouling Flotation Alternate Low-Pressure Flotation Water Performance Membrane Alternate Ultrafiltration / Floatation Potable Water Microfiltration Alternate UF/MF DAF Google Scholar Scopus Database AMTA Digital Library Iterative Process Fouling Metrics Chemical Clean Cycle, n Hydraulic Backwash )aPk( PMT Studies use a wide array of fouling metrics to quantify membrane fouling:  Fouling Indices  Fouling Rates  Critical Flux  Permeability Decline  Transmembrane Pressure (TMP) Chemical Clean P n, i+ P n, i t cc Filtration Time (h) C-IN Outside-in PVDF hollow-fiber Inside-out tubular multi-channel PES CF-DAF 1.34x 63..83xx CF-DAF  Mixed results from past studies (e.g., Braghetta et al.,(1997); Hög et al.,(2015)).  For the same water and coagulation chemistry, relative LPM performance after the different pretreatments changed with membrane type.  Proposal of critical threshold value for solids mass loading. CF-SED CF-SED CF-DAF CF-DAF CF-SED Outside-in PVDF hollow-fiber Inside-out tubular multi-channel PES Two different membrane types→ CF-DAF and CF-SED perform similarly.  Polymer use does not seem to impact downstream LPM fouling over short term. CF-SED Study similarities:  Raw water quality.  Practically identical coagulation chemistry.  Membrane operation.  Same nominal molecular weight cutoff. Membrane Fouling: Impact of DAF Treated Water Quality  CF-DAF conditions optimized for the removal of hydrophobic (HPO) NOM lowered FR . cirr  Limitations:  Developed using primarily a single colored river water.  Water has very low biopolymer concentration (~ 150 μg/L). Dissolved air flotation pretreatment for low-pressure membranes in water treatment: A review of fouling mitigation and product water quality. Reduced low-pressure membrane fouling by inline coagulation pretreatment for a colored river water. The use of integrated flotation and ceramic membrane filtration for surface water treatment with high loads of suspended and dissolved organic matter. Comparing sedimentation, flotation, and in-line pretreatment for low-pressure membrane fouling reduction. Hollow fiber ultrafiltration of Ottawa River water: Floatation versus sedimentation pretreatment. Improved membrane pretreatment of high hydrophobic natural organic matter (NOM) waters by floatation.