Staff publications (SAS)

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Browsing Staff publications (SAS) by Subject "Activated sludge"

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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.
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    Nitrous oxide emissions for early warning of biological nitrification failure in activated sludge.
    (Elsevier Science B.V., Amsterdam., 2009-03-01T00:00:00Z) Butler, Mark D.; Wang, Yayi; Cartmell, Elise; Stephenson, Tom
    Experiments were carried out to establish whether nitrous oxide (N2O) could be used as a non-invasive early warning indicator for nitrification failure. Eight experiments were undertaken; duplicate shocks DO depletion, influent ammonia increases, allylthiourea (ATU) shocks and sodium azide (NaN3) shocks were conducted on a pilot-scale activated sludge plant which consisted of a 315 L completely mixed aeration tank and 100 L clarifier. The process performed well during pre-shock stable operation; ammonia removals were up to 97.8% and N2O emissions were of low variability (<0.5 ppm). However, toxic shock loads produced an N2O response of a rise in off-gas concentrations ranging from 16.5 to 186.3 ppm, followed by a lag-time ranging from 3 to 5 h ((0.43–0.71) × HRT) of increased NH3-N and/or NO2− in the effluent ranging from 3.4 to 41.2 mg L−1. It is this lag-time that provides the early warning for process failure, thus mitigating action can be taken to avoid nitrogen contamination of receiving