Browsing by Author "Ketley, David Andrew"

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    The effect of fully anoxic conditions and frequency of exposure to anoxic and aerobic conditions on the growth of low F/M filaments in nitrogen remova
    (1991) Ketley, David Andrew; Ekama, George A
    Filamentous bulking, caused predominantly by low F/M filaments (Blackbeard et al, 1986, 1988), results in considerable settling problems in full scale nitrogen (N) and nutrient (N & P) removal activated sludge plants in South Africa. The development of specific methods for control of low F/M filaments in these plants would lead to significant savings because higher flows and loads could be treated in existing plants. From the findings of Blackbeard et al (1986, 1988) an extensive research project was undertaken by Gabb et al (1989a) into specific control of low F/M filament bulking. This project investigated the effectiveness of selectors, the proposed method of low F/M filamentous bulking control and found them to be ineffective. Consequently a second comprehensive laboratory research investigation was commenced in 1989. The work presented in this thesis forms a part of this investigation; the experimental investigation was conducted in 3 phases investigating (1) the effect of fully anoxic conditions and low nitrate concentrations during the anoxic phase of an intermittent aeration cycle on low F/M filament growth in continuously fed completely mixed single reactor systems receiving a synthetic sewage feed; (2) the effect of fully anoxic conditions on low F/M filament growth in continuously fed completely mixed single reactor systems receiving real sewage; and (3) the effect of alternating the frequency of exposure of low F/M filaments to anoxic/aerobic conditions (i.e. increasing the length of the aeration cycle but maintaining the aerobic mass fraction) in intermittently aerated continuously fed single completely mixed reactor systems receiving real sewage.