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Nonoxidative removal of organics in the activated sludge process.

Modin O, Persson F, Wilén BM, Hermansson M - Crit Rev Environ Sci Technol (2016)

Bottom Line: Sorption onto activated sludge can remove a large fraction of the colloidal and particulate wastewater organics.Intracellular storage of, e.g., polyhydroxyalkanoates (PHA), triacylglycerides (TAG), or wax esters can convert wastewater organics into precursors for high-value products.Better utilization of nonoxidative processes in activated sludge could reduce the wasteful aerobic oxidation of organic compounds and lead to more resource-efficient wastewater treatment plants.

View Article: PubMed Central - PubMed

Affiliation: Division of Water Environment Technology, Department of Civil and Environmental Engineering, Chalmers University of Technology , Gothenburg , Sweden.

ABSTRACT

The activated sludge process is commonly used to treat wastewater by aerobic oxidation of organic pollutants into carbon dioxide and water. However, several nonoxidative mechanisms can also contribute to removal of organics. Sorption onto activated sludge can remove a large fraction of the colloidal and particulate wastewater organics. Intracellular storage of, e.g., polyhydroxyalkanoates (PHA), triacylglycerides (TAG), or wax esters can convert wastewater organics into precursors for high-value products. Recently, several environmental, economic, and technological drivers have stimulated research on nonoxidative removal of organics for wastewater treatment. In this paper, we review these nonoxidative removal mechanisms as well as the existing and emerging process configurations that make use of them for wastewater treatment. Better utilization of nonoxidative processes in activated sludge could reduce the wasteful aerobic oxidation of organic compounds and lead to more resource-efficient wastewater treatment plants.

No MeSH data available.


Schematic of an adsorption–biooxidation (AB) process.
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f0006: Schematic of an adsorption–biooxidation (AB) process.

Mentions: The adsorption–biooxidation process consists of two activated sludge stages in series (Figure 6), each with its own secondary settler. The first stage (A-stage) receives a high organic load with an F/M ratio ranging from 2 to 10 gBOD/gVSS· day, an SRT of 3–12 hr, and an HRT of 30 min or less. Organic matter is removed primarily by sorption onto the activated sludge flocs. The second stage (B-stage) is low loaded with an F/M ratio of less than 0.1 gBOD/gVSS· day. The B-stage is operated with long SRT of 8–20 days and biological nitrogen removal through nitrification and denitrification can be achieved. The process was developed at the municipal wastewater treatment plant in Krefeld, Germany, which because of industrial discharges received a wastewater with high degree of variability in pH and toxicity. The A-stage was able to cope with toxic shocks and made the problematic wastewater of Krefeld biologically treatable. The first full-scale AB plant was installed in 1980. Since then, several full-scale plants have been installed (Versprille et al., 1985; Boehnke et al., 1997a, 1997b; Boehnke et al., 1998). Garcia-Olivares and Becares (1995) developed a mathematical model predicting COD in the final effluent and MLSS concentrations in the reactors. They calibrated the model against data from a pilot reactor by varying the growth rate, specific substrate removal rate, and concentration factor in the settling tank parameters. However, they did not include sorption kinetics in the A-stage as a specific mechanism in the model. Nogaj et al. (2015) developed a modified version of the ASM1 model to describe organics removal in A-stage activated sludge. As previous research has shown that activated sludge operated at very short SRT is only able to utilize the most easily biodegradable fraction of the organics (Haider et al., 2003), they divided the soluble organics into two fractions: rapidly and slowly biodegradable substrate. They also included EPS production, storage of soluble organics, and sorption of colloidal organics as specific mechanisms in the model. The model was calibrated and validated against process data from two high-rate activated sludge pilot plants (Nogaj et al., 2015).Figure 6.


Nonoxidative removal of organics in the activated sludge process.

Modin O, Persson F, Wilén BM, Hermansson M - Crit Rev Environ Sci Technol (2016)

Schematic of an adsorption–biooxidation (AB) process.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940897&req=5

f0006: Schematic of an adsorption–biooxidation (AB) process.
Mentions: The adsorption–biooxidation process consists of two activated sludge stages in series (Figure 6), each with its own secondary settler. The first stage (A-stage) receives a high organic load with an F/M ratio ranging from 2 to 10 gBOD/gVSS· day, an SRT of 3–12 hr, and an HRT of 30 min or less. Organic matter is removed primarily by sorption onto the activated sludge flocs. The second stage (B-stage) is low loaded with an F/M ratio of less than 0.1 gBOD/gVSS· day. The B-stage is operated with long SRT of 8–20 days and biological nitrogen removal through nitrification and denitrification can be achieved. The process was developed at the municipal wastewater treatment plant in Krefeld, Germany, which because of industrial discharges received a wastewater with high degree of variability in pH and toxicity. The A-stage was able to cope with toxic shocks and made the problematic wastewater of Krefeld biologically treatable. The first full-scale AB plant was installed in 1980. Since then, several full-scale plants have been installed (Versprille et al., 1985; Boehnke et al., 1997a, 1997b; Boehnke et al., 1998). Garcia-Olivares and Becares (1995) developed a mathematical model predicting COD in the final effluent and MLSS concentrations in the reactors. They calibrated the model against data from a pilot reactor by varying the growth rate, specific substrate removal rate, and concentration factor in the settling tank parameters. However, they did not include sorption kinetics in the A-stage as a specific mechanism in the model. Nogaj et al. (2015) developed a modified version of the ASM1 model to describe organics removal in A-stage activated sludge. As previous research has shown that activated sludge operated at very short SRT is only able to utilize the most easily biodegradable fraction of the organics (Haider et al., 2003), they divided the soluble organics into two fractions: rapidly and slowly biodegradable substrate. They also included EPS production, storage of soluble organics, and sorption of colloidal organics as specific mechanisms in the model. The model was calibrated and validated against process data from two high-rate activated sludge pilot plants (Nogaj et al., 2015).Figure 6.

Bottom Line: Sorption onto activated sludge can remove a large fraction of the colloidal and particulate wastewater organics.Intracellular storage of, e.g., polyhydroxyalkanoates (PHA), triacylglycerides (TAG), or wax esters can convert wastewater organics into precursors for high-value products.Better utilization of nonoxidative processes in activated sludge could reduce the wasteful aerobic oxidation of organic compounds and lead to more resource-efficient wastewater treatment plants.

View Article: PubMed Central - PubMed

Affiliation: Division of Water Environment Technology, Department of Civil and Environmental Engineering, Chalmers University of Technology , Gothenburg , Sweden.

ABSTRACT

The activated sludge process is commonly used to treat wastewater by aerobic oxidation of organic pollutants into carbon dioxide and water. However, several nonoxidative mechanisms can also contribute to removal of organics. Sorption onto activated sludge can remove a large fraction of the colloidal and particulate wastewater organics. Intracellular storage of, e.g., polyhydroxyalkanoates (PHA), triacylglycerides (TAG), or wax esters can convert wastewater organics into precursors for high-value products. Recently, several environmental, economic, and technological drivers have stimulated research on nonoxidative removal of organics for wastewater treatment. In this paper, we review these nonoxidative removal mechanisms as well as the existing and emerging process configurations that make use of them for wastewater treatment. Better utilization of nonoxidative processes in activated sludge could reduce the wasteful aerobic oxidation of organic compounds and lead to more resource-efficient wastewater treatment plants.

No MeSH data available.