Abstract
The biological kinetic Activated Sludge Model No. 1 (ASM1, Henze et al., 1987; Dold et al., 1991) for carbon (C) and nitrogen (N) removal is integrated with the mixed weak acid/base model of Musvoto et al. (1997, 2000a,b,c) to extend application of ASM1 to situations where an estimate for pH is important. Because chemical precipitation is generally not significant when treating municipal wastewaters for C and N removal, only gas and liquid phase processes were considered for this integrated model. The biological processes in ASM1 were modified to take into account the effect of the interaction of the weak acid/ base species of the ammonia, carbonate and phosphate systems and pH on heterotrophic and autotrophic organism behaviour, which includes generation and utilisation CO 2 in metabolism, use of specific weak acid/base species for organism growth and generation and utilisation of H + . With these modifications, simulations with the model were compared with those of ASM1 and experimental data in the literature; a good correlation was obtained. However, these comparisons are only a preliminary validation, because, despite their inclusion, the weak acid/bases and pH do not have a significant effect on the biological processes in the cases considered (i.e. well buffered wastewater). A difficulty in calibrating this model is selection of the kLA value for the aeration system, which affects the pH in the anoxic and aerobic reactors through CO 2 gas exchange. Aerobic reactor outflows from two full-scale wastewater treatment plants with fine bubble aeration systems were found to be around 20% supersaturated with CO2. The performance of a ND activated sludge system with low influent alkalinity is evaluated.
Highlights
The biological kinetic Activated Sludge Model No 1 (ASM1, Henze et al, 1987; Dold et al, 1991) for carbon (C) and nitrogen (N) removal is integrated with the mixed weak acid/base model of Musvoto et al (1997, 2000a,b,c) to extend application of ASM1 to situations where an estimate for pH is important
The biological processes in ASM1 were modified to take into account the effect of the interaction of the weak acid/ base species of the ammonia, carbonate and phosphate systems and pH on heterotrophic and autotrophic organism behaviour, which includes generation and utilisation CO2 in metabolism, use of specific weak acid/base species for organism growth and generation and utilisation of H+
A number of mathematical models describing the kinetics of the biological processes for carbon (C), nitrogen (N) and phosphorus (P) removal by the activated sludge system have been developed, e.g. the C and N removal models of van Haandel et al (1981) and Activated Sludge Model No 1 (ASM1, Henze et al, 1987), and the C, N and P removal models UCTPHO (Wentzel et al, 1992) and ASM2 and 2d (Henze et al, 1995, 1999)
Summary
A number of mathematical models describing the kinetics of the biological processes for carbon (C), nitrogen (N) and phosphorus (P) removal by the activated sludge system have been developed, e.g. the C and N removal models of van Haandel et al (1981) and Activated Sludge Model No 1 (ASM1, Henze et al, 1987), and the C, N and P removal models UCTPHO (Wentzel et al, 1992) and ASM2 and 2d (Henze et al, 1995, 1999). The biological processes of C and N removal in activated sludge systems are integrated into the three phase mixed weak acid/base chemical-physical kinetic model developed by Musvoto et al (1997, 2000a,b,c).
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