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The influence of a particulate substrate on filamentous bulking and phosphorus removal in activated sludge systems
Wat. Res. Vol. 25, No. 9, p. 1161. 1991 Printed in Great Britain
0043-1354/91 $3.00+0.00 Pergamon Press plc
COMMENT C o m m e n t o n " T h e influence o f a p a r t i c u l a t e s u b s t r a t e on filamentous b u l k i n g a n d p h o s p h o r u s r e m o v a l in a c t i v a t e d sludge s y s t e m s " b y J. W A ~ R a n d L. NOV~,K, Wat. Res. 24, 573-581 (1990). In his book, Busch (1971) has written: "The selection of an experimental system immediately imposes constraints upon the work to be done and to a greater or lesser extent, pre-determines the results obtained from a study." The paper of Wanner and Novfik has failed to recognize the effect of such constraints. Although it was shown 17 years ago (Chudoba et aL, 1973) that the minimum number of compartments necessary to suppress filamentous bulking in an oxic system was eight (preferably with a dispersion number below 0.1), the authors used in their experimental system only three. Due to the improperly designed system, they had problems with filamentous bulking. The problems were also due to using glucose in the multicomponent substrate. Although it was emphasized (Doh/myos et al., 1970; {~ech and Chudoba, 1983) that glucose has quite exceptional behaviour and position among other substrates, the substrate used by the authors contained up to 25% of glucose as COD. Such a high proportion cannot be found in any sewage. Some industrial wastwaters contain saccharose, lactose or starch rather than glucose. The results obtained in period 3 clearly showed that the particulate substrate used did not support bulking in either system. Consequently, the hydrolysis hypothesis formulated by Ekama and Marais (1986) was shown to be doubtful. Unfortunately, the authors have not concluded this clearly. The higher SVI values obtained in the CM system during period 2 were evidently due to the presence of glucose in the multicomponent substrate. The particulate fraction is defined in most textbooks on water chemistry as that having a mean diameter above 0.4/tm. Consequently, soluble high molecular polymers cannot be stated to be a "particulate substrate". Otherwise, we will not understand one another. Department o f Water Technology and Environmental Engineering Prague Institute o f Chemical Technology Technickh 5, CS-I66 28 Prague 6 Czechoslovakia
JAN CHUDOBA~
REFERENCES
Busch A. W. (1971) Aerobic Biological Treatment of Waste Waters. Principles and Practice, p. 3. Oligodynamics Press, Houston. ~ech J. S. and Chudoba J. (1983) Influence of accumulation capacity of activated sludge microorganisms on kinetics of glucose removal. Wat. Res. 17, 659-666. Chudoba J., Ottovfi V. and Mad6ra V. (1973) Control of activated sludge filamentous bulking--I. Effect of the hydraulic regime or degree of mixing in an aeration tank. Wat. Res. 7, 1163-1182. Dohfinyos M., Grau P. and Chudoba J. (1970) Kinetic assessment of glucose removal and saccharide accumulation capacities in activated sludge. Proc. IAWPR Conference, Pap. No. II-3, San Francisco. Ekama G. A. and Marais G. v. R. (1986) The implication of the IAWPRC hydrolysis hypothesis on low F/M bulking. Wat. Sci. Technol. 18, 11-19.
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0043-1354/91 $3.00+0.00 Pergamon Press plc
COMMENT C o m m e n t o n " T h e influence o f a p a r t i c u l a t e s u b s t r a t e on filamentous b u l k i n g a n d p h o s p h o r u s r e m o v a l in a c t i v a t e d sludge s y s t e m s " b y J. W A ~ R a n d L. NOV~,K, Wat. Res. 24, 573-581 (1990). In his book, Busch (1971) has written: "The selection of an experimental system immediately imposes constraints upon the work to be done and to a greater or lesser extent, pre-determines the results obtained from a study." The paper of Wanner and Novfik has failed to recognize the effect of such constraints. Although it was shown 17 years ago (Chudoba et aL, 1973) that the minimum number of compartments necessary to suppress filamentous bulking in an oxic system was eight (preferably with a dispersion number below 0.1), the authors used in their experimental system only three. Due to the improperly designed system, they had problems with filamentous bulking. The problems were also due to using glucose in the multicomponent substrate. Although it was emphasized (Doh/myos et al., 1970; {~ech and Chudoba, 1983) that glucose has quite exceptional behaviour and position among other substrates, the substrate used by the authors contained up to 25% of glucose as COD. Such a high proportion cannot be found in any sewage. Some industrial wastwaters contain saccharose, lactose or starch rather than glucose. The results obtained in period 3 clearly showed that the particulate substrate used did not support bulking in either system. Consequently, the hydrolysis hypothesis formulated by Ekama and Marais (1986) was shown to be doubtful. Unfortunately, the authors have not concluded this clearly. The higher SVI values obtained in the CM system during period 2 were evidently due to the presence of glucose in the multicomponent substrate. The particulate fraction is defined in most textbooks on water chemistry as that having a mean diameter above 0.4/tm. Consequently, soluble high molecular polymers cannot be stated to be a "particulate substrate". Otherwise, we will not understand one another. Department o f Water Technology and Environmental Engineering Prague Institute o f Chemical Technology Technickh 5, CS-I66 28 Prague 6 Czechoslovakia
JAN CHUDOBA~
REFERENCES
Busch A. W. (1971) Aerobic Biological Treatment of Waste Waters. Principles and Practice, p. 3. Oligodynamics Press, Houston. ~ech J. S. and Chudoba J. (1983) Influence of accumulation capacity of activated sludge microorganisms on kinetics of glucose removal. Wat. Res. 17, 659-666. Chudoba J., Ottovfi V. and Mad6ra V. (1973) Control of activated sludge filamentous bulking--I. Effect of the hydraulic regime or degree of mixing in an aeration tank. Wat. Res. 7, 1163-1182. Dohfinyos M., Grau P. and Chudoba J. (1970) Kinetic assessment of glucose removal and saccharide accumulation capacities in activated sludge. Proc. IAWPR Conference, Pap. No. II-3, San Francisco. Ekama G. A. and Marais G. v. R. (1986) The implication of the IAWPRC hydrolysis hypothesis on low F/M bulking. Wat. Sci. Technol. 18, 11-19.
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