Browsing by Author "Stuetz, Richard M."
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Item Open Access Dinitrogen oxide production by a mixed culture of nitrifying bacteria during ammonia shock loading and aeration failure(Springer, 2002-12-01T00:00:00Z) Burgess, Joanna E.; Colliver, Bettina B.; Stuetz, Richard M.; Stephenson, TomA number of experiments was conducted in order to establish if N2O in the exhaust gas from an aerobic consortium of nitrifiers could be used as an indicator for monitoring the nitrification process. Laboratory-scale experiments with an activated sludge system showed a strong correlation between ammonia shock loads and both the concentration of N2O and the rate of increase of N2O in the exhaust gas for shock loads less than 1.60 mg ammonical nitrogen (NH3-N) per g total suspended solids (TSS). For greater ammonia shock loads, correlation was found between build-up of nitrite in the aeration tank and the concentration of N2O in the exhaust gas from the tank. When subjecting the system to aeration failure, a similar pattern was seen, with a correlation between nitrite build-up in the aeration tank and increases in the concentration of N2O in the exhaust gas. The results from this work suggest that the changes in N2O concentration in the exhaust gas from a nitrifying process may be a useful parameter for monitoring such processes.Item Open Access Membrane Gas Absorbers for H2S Removal - Design, Operation and Technology Integration into Existing Odour Treatment Strategies.(Taylor & Francis, 2005-07-01T00:00:00Z) Jefferson, Bruce; Nazareno, C.; Georgaki, S.; Gostelow, P.; Stuetz, Richard M.; Longhurst, Philip J.; Robinson, T.A hollow fibre (HF) polypropylene membrane gas absorber was investigated for the removal of hydrogen sulphide (H2S) from gas streams. Gas concentrations between 25-2010 ppmV were fed into the shell side of a membrane module whilst water-NaOH solutions flowed counter-currently in the fibre lumens. The process was effective at removing the H2S (96% at G:L ratios up to 50 and pH 13) from the gas phase in a single pass through the membrane at all the concentrations of H2S investigated. Analysis of the mass transfer process revealed the rate of transfer to be controlled by the gas phase transfer coefficient with a value between 1 and 25Ã 10-4 m.s-1. The possible integration of a membrane absorber system into existing odour treatment strategies was assessed by comparing the membrane system, based on the experimentally determined mass transfer coefficient, with existing full scale biofiltration plants. The membrane system became economically favourable at gas flow rates lower than 1630 m3.h-1Item Open Access The role of algal organic matter in the separation of algae and cyanobacteria using the novel “Posi” - Dissolved air flotation process(Elsevier, 2017-11-23) Rao Hanumanth Rao, Narasinga; Yap, Russell; Whittaker, Michael; Stuetz, Richard M.; Jefferson, Bruce; Peirson, William L.; Granville, Anthony M.; Henderson, Rita K.Algae and cyanobacteria frequently require separation from liquid media in both water treatment and algae culturing for biotechnology applications. The effectiveness of cell separation using a novel dissolved air flotation process that incorporates positively charged bubbles (PosiDAF) has recently been of interest but has been shown to be dependent on the algae or cyanobacteria species tested. Previously, it was hypothesised that algal organic matter (AOM) could be impacting the separation efficiency. Hence, this study investigates the influence of AOM on cell separation using PosiDAF, in which bubbles are modified using a commercially available cationic polyelectrolyte poly(N, N-diallyl-N,N-dimethylammonium chloride) (PDADMAC). The separation of Chlorella vulgaris CS-42/7, Mychonastes homosphaera CS-556/01 and two strains of Microcystis aeruginosa (CS-564/01 and CS-555/1), all of which have similar cell morphology but different AOM character, was investigated. By testing the cell separation in the presence and absence of AOM, it was determined that AOM enhanced cell separation for all the strains but to different extents depending on the quantity and composition of carbohydrates and proteins in the AOM. By extracting AOM from the strain for which optimal separation was observed and adding it to the others, cell separation improved from <55% to >90%. This was attributed to elevated levels of acidic carbohydrates as well as glycoprotein-carbohydrate conjugations, which in turn were related to the nature and quantity of proteins and carbohydrates present in the AOM. Therefore, it was concluded that process optimisation requires an in-depth understanding of the AOM and its components. If culturing algae for biotechnology applications, this indicates that strain selection is not only important with respect to high value product content, but also for cell separation.