Browsing by Author "Pearce, Peter"

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    Biomass effects on oxygen transfer in membrane bioreactors.
    (Elsevier, 2007-03) Germain, Eve; Nelles, F.; Drews, A.; Pearce, Peter; Kraume, M.; Reid, E.; Judd, Simon J.; Stephenson, Tom
    Ten biomass samples from both municipal and industrial pilot and full scale submerged membrane bioreactors (MBRs) with mixed liquor suspended solids concentrations (MLSS) ranging from 7.2 to 30.2 g L−1 were studied at six air-flow rates (0.7, 1.3, 2.3, 3, 4.4 and 6 m3 m−3 h−1). Statistical analyses were applied to identify the relative impacts of the various bulk biomass characteristics on oxygen transfer. Of the biomass characteristics studied, only solids concentration (correlated with viscosity), the carbohydrate fraction of the EPS (EPSc) and the chemical oxygen demand (COD) concentration of the SMP (SMPCOD) were found to affect the oxygen transfer parameters kLa20 (the oxygen transfer coefficient) and α-factor. The relative influence on kLa20 was MLSS>aeration>EPSc>SMPCOD and on α-factor was MLSS>SMPCOD>EPSc>aeration. Both kLa20 and α-factor increased with increasing aeration and EPSc and decreased with increasing MLSS and SMPCOD. MLSS was found to be the main parameter controlling the oxygen transfer.
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    Mechanical sludge disintegration for the production of carbon source for biological nutrient removal.
    (Elsevier, 2007-04) Kampas, Pantelis; Parsons, Simon A.; Pearce, Peter; Ledoux, Sandrine; Vale, Peter C. J.; Churchley, J.; Cartmell, Elise
    The primary driver for a successful biological nutrient removal is the availability of suitable carbon source, mainly in the form of volatile fatty acids (VFA). Several methods have been examined to increase the amount of VFAs in wastewater. This study investigates the mechanism of mechanical disintegration of thickened surplus activated sludge by a deflaker technology for the production of organic matter. This equipment was able to increase the soluble carbon in terms of VFA and soluble chemical oxygen demand (SCOD) with the maximum concentration to be around 850 and 6530 mg l−1, for VFA and SCOD, respectively. The particle size was reduced from 65.5 to 9.3 μm after 15 min of disintegration with the simultaneous release of proteins (1550 mg l−1) and carbohydrates (307 mg l−1) indicating floc disruption and breakage. High performance size exclusion chromatography investigated the disintegrated sludge and confirmed that the deflaker was able to destroy the flocs releasing polymeric substances that are typically found outside of cells. When long disintegration times were applied (10 min or 9000 kJ kg−1 TS of specific energy) smaller molecular size materials were released to the liquid phase, which are considered to be found inside the cells indicating cell lysis.