Investigating the Structure of Activated Sludge Flocs: Morphologic and Compositional Characterization of Surface and Bulk Components
Abstract:Environmental scanning electron microscopy (ESEM) with an energy dispersive x-ray spectrometer (EDX) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were demonstrated to be useful analytical tools for investigating surface and bulk components of individual floc particles from both full- and bench-scale activated sludge systems. Detailed surface imaging of various hydrated biological floc particles by ESEM revealed substantial differences in surface characteristics between treatment systems while elemental mapping by EDX revealed differences in iron and aluminum distributions. ToF-SIMS revealed signature fragments of protein and polysaccharide material from the floc surface, suggesting this technique is capable of surface profiling extracellular polymeric substances derived from wastewater treatment systems. However, neither iron nor aluminum were found in the ToF-SIMS spectra suggesting that these cations are not located within the top 1 – 2 nm of the floc surface. Principle Component Analysis of the positive ion ToF-SIMS spectra from the mixed liquor suspended solid (MLSS) samples and reference aquatic organic materials revealed slight differences between the full- and bench-scale MLSS surface properties but substantial differences among MLSS and treated effluent from the same facility.
Document Type: Research Article
Publication date: January 1, 2004
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