Development of a mechanistic model for biological nutrient removal activated sludge systems and application to a full-scale WWTP

Filamentous bulking and the long sludge age required for nitrification are two important factors that limit the wastewater treatment capacity of biological nutrient removal (BNR) activated sludge systems. A growing body of observations from full-scale plants indicate support for the hypothesis that a significant stimulus for filamentous bulking in BNR systems in alternating anoxic-aerobic conditions with the presence of oxidized nitrogen at the transition from anoxic to aerobic. In the DEPHANOX system, nitrification takes place externally allowing sludge age and filamentous bulking to be reduced and increases treatment capacity. Anoxic P uptake is exploited in this system but it appears that this form of biological excess P removal (BEPR) is significantly reduced compared with aerobic P uptake in conventional BNR systems. Developments in the understanding of the BEPR processes of (i) phosphate accumulating organism (PAO) denitrification and anoxic P uptake, (ii) fermentation of influent readily biodegradable (RB)COD and (iii) anaerobic hydrolysis of slowly biodegradable (SB)COD are evaluated in relation to the IAWQ Activated Sludge Model (ASM) No.2. Recent developments in BEPR research do not yet allow a significant improvement to be made to ASM No. 2 that will increase its predictive power and reliability and therefore it remains essentially as a framework to guide further research.

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Anoxic growth of phosphate-accumulating organisms (PAOs) in biological nutrient removal activated sludge systems

Water Research ◽

10.1016/s0043-1354(02)00186-0 ◽

2002 ◽

Vol 36 (19) ◽

pp. 4927-4937 ◽

Cited By ~ 102

Author(s):

Zhi-rong Hu ◽

M.C Wentzel ◽

G.A Ekama

Keyword(s):

Activated Sludge ◽

Nutrient Removal ◽

Biological Nutrient Removal ◽

Activated Sludge Systems

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A comparison of biological nutrient removal in intermittent cyclic and continuous activated sludge systems

Resources Conservation and Recycling ◽

10.1016/0921-3449(94)90086-8 ◽

1994 ◽

Vol 11 (1-4) ◽

pp. 149-159 ◽

Cited By ~ 3

Author(s):

Kin-man Ho ◽

Paul F. Greenfield ◽

Linda L. Blackall ◽

Peter R.F. Bell ◽

Andre Krol

Keyword(s):

Activated Sludge ◽

Nutrient Removal ◽

Biological Nutrient Removal ◽

Activated Sludge Systems

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Sludge production and oxygen demand in nutrient removal activated sludge systems

Water Science & Technology ◽

10.2166/wst.1996.0533 ◽

1996 ◽

Vol 34 (5-6) ◽

pp. 43-50 ◽

Cited By ~ 5

Author(s):

P. S. Barker ◽

P. L. Dold

Keyword(s):

Oxygen Consumption ◽

Activated Sludge ◽

Nutrient Removal ◽

Suspended Solids ◽

Model Simulation ◽

Oxygen Demand ◽

Biological Nutrient Removal ◽

Solids Concentration ◽

Volatile Solids ◽

Activated Sludge Systems

Results of model simulations indicate that without the assumption of COD loss, predictions of oxygen consumption and volatile suspended solids production are significantly over-estimated for biological excess phosphorus removal (BEPR) activated sludge systems (and to a lesser extent anoxic-aerobic systems). These systems apparently consume less oxygen and produce less volatile solids than aerobic systems for the same amount of COD removal. A general model for biological nutrient removal systems has recently been presented by Barker and Dold. Three mechanisms for COD loss are suggested, based on results of COD balances for different types of activated sludge system. Model simulation results with and without the assumption of COD loss are discussed, as well as the influence of influent COD composition on predictions of volatile suspended solids concentration/production and oxygen consumption.

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