Structural, physicochemical and microbial properties of flocs and biofilms in integrated fixed-film activated sludge (IFFAS) systems

摘要: Abstract Integrated fixed-film activated sludge systems (IFFAS) may achieve year-round nitrification or gain additional treatment capacity due to the presence of both flocs and biofilms, potential for multiple redox states long solids retention time. Flocs biofilms are distinctive microbial structures characterization physicochemical structural properties these provide insight into their respective roles in wastewater contaminant removal IFFAS. were examined from five different pilot media being evaluated full scale implementation at a large municipal plant. within same system possessed surface characteristics; found have higher negative charge (−0.35 −0.65 meq./g VSS) more hydrophobic (60%–75%) than (−0.05 −0.07 meq/g VSS; 19–34%). The EPS content was significantly (range 2.1–4.5 folds) that biofilms. In floc-derived extracellular polymeric substances (EPS), protein (PN) clearly dominant; whereas biofilm-derived EPS, PN polysaccharide (PS) present approximately equal proportions. Biofilm had proportion DNA when compared flocs. growth preferential on protected internal surfaces media. Colonization external evident by small microcolonies. heterogeneity supported observed differences biomass content, thickness roughness biofilm surface. interior be patchy with clusters cells connected an irregular arrangement interconnecting projections. ranged between 139 μm 253 μm. pattern oxygen penetration is expected complex. Nitrifiers denitrifiers predominantly associated latter dispersed throughout film arranged micro-clusters, suggesting partial penetration.