Bioflocculation of mesophilic and thermophilic activated sludge

Autor: A. de Keizer, J.C.T. Vogelaar, Gatze Lettinga, S. Spijker
Rok vydání: 2005
Předmět:
Polymers
Laboratorium voor Fysische chemie en Kolloïdkunde
Waste Disposal
Fluid
Bioreactors
activated sludge
biological treatment
Physical Chemistry and Colloid Science
Waste Management and Disposal
Water Science and Technology
Sewage
afvalwaterbehandeling
Chemistry
Ecological Modeling
Pollution
Aerobiosis
Bacteria
Aerobic
Wastewater
temperatures
biologische behandeling
Milieutechnologie
Sewage treatment
Shear Strength
Mesophile
Paper
hydrofobiciteit
Flocculation
Environmental Engineering
water
Industrial Waste
flocs
flocculation
temperatuur
Bioreactor
Particle Size
hydrophobicity
paper-mill
Civil and Structural Engineering
WIMEK
adsorptie
geactiveerd slib
reactors
Environmental engineering
temperature
uitvlokking
Oxygen
Activated sludge
waste water treatment
Chemical engineering
adsorption
Environmental Technology
DLVO theory
whitewater
effluent
Waste disposal
Zdroj: Water Research 39 (2005) 1
Water Research, 39(1), 37-46
ISSN: 0043-1354
Popis: Thermophilic activated sludge treatment is often hampered by a turbid effluent. Reasons for this phenomenon are so far unknown. Here, the hypothesis of the temperature dependency of the hydrophobic interaction as a possible cause for diminished thermophilic activated sludge bioflocculation was tested. Adsorption of wastewater colloidal particles was monitored on different flat surfaces as a function of temperature. Adsorption on a hydrophobic surface varied with temperature between 20 and 60 degrees C and no upward or downward trend could be observed. This makes the hydrophobic interaction hypothesis unlikely in explaining the differences in mesophilic and thermophilic activated sludge bioflocculation. Both mesophilic and thermophilic biomass did not flocculate with wastewater colloidal particles under anaerobic conditions. Only in the presence of oxygen, with biologically active bacteria, the differences in bioflocculation behavior became evident. Bioflocculation was shown only to occur with the combination of wastewater and viable mesophilic biomass at 30 degrees C, in the presence of oxygen. Bioflocculation did not occur in case the biomass was inactivated or when oxygen was absent. Thermophilic activated sludge hardly showed any bioflocculation, also under mesophilic conditions. Despite the differences in bioflocculation behavior, sludge hydrophobicity and sludge zetapotentials were almost similar. Theoretical calculations using the DLVO (Derjaguin, Landau, Verweij and Overbeek) theory showed that flocculation is unlikely in all cases due to long-range electrostatic forces. These calculations, combined with the fact that bioflocculation actually did occur at 30 degrees C and the unlikelyness of the hydrophobic interaction, point in the direction of bacterial exo-polymers governing bridging flocculation. Polymer interactions are not included in the DLVO theory and may vary as a function of temperature.
Databáze: OpenAIRE
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