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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 a contact-stabilization wastewater treatment plant.
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f0005: Schematic of a contact-stabilization wastewater treatment plant.

Mentions: In the contact-stabilization process, the wastewater is mixed with activated sludge in a contact tank with low hydraulic retention time. Removal of organics is assumed to take place mainly by sorption onto the activated sludge flocs. The treated water is then separated from the flocs in a sedimentation tank. The concentrated sludge is regenerated in an aerated stabilization tank where the organics sorbed onto the sludge are oxidized (Figure 5) (Rittmann and McCarty, 2001). The process was patented by Coombs (1922), and later also developed by Ullrich and Smith (1951). The latter used hydraulic retention times of 15 min in the contact tank, 65 min in the settler, and 90 min in the stabilization tank and achieved 90–95% reductions of suspended solids and BOD in the influent wastewater (Ullrich and Smith, 1951). As the main removal mechanism of organic matter from the wastewater is sorption onto the activated sludge flocs, it is most suitable for treatment of wastewater with a low fraction of soluble organics and a high fraction of colloidal or particulate organics (Sarioglu et al., 2003). A higher removal of soluble organics can be attained with a higher sludge recirculation ratio. However, then the process becomes similar to a completely mixed reactor (Gujer and Jenkins, 1975).Figure 5.


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 a contact-stabilization wastewater treatment plant.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f0005: Schematic of a contact-stabilization wastewater treatment plant.
Mentions: In the contact-stabilization process, the wastewater is mixed with activated sludge in a contact tank with low hydraulic retention time. Removal of organics is assumed to take place mainly by sorption onto the activated sludge flocs. The treated water is then separated from the flocs in a sedimentation tank. The concentrated sludge is regenerated in an aerated stabilization tank where the organics sorbed onto the sludge are oxidized (Figure 5) (Rittmann and McCarty, 2001). The process was patented by Coombs (1922), and later also developed by Ullrich and Smith (1951). The latter used hydraulic retention times of 15 min in the contact tank, 65 min in the settler, and 90 min in the stabilization tank and achieved 90–95% reductions of suspended solids and BOD in the influent wastewater (Ullrich and Smith, 1951). As the main removal mechanism of organic matter from the wastewater is sorption onto the activated sludge flocs, it is most suitable for treatment of wastewater with a low fraction of soluble organics and a high fraction of colloidal or particulate organics (Sarioglu et al., 2003). A higher removal of soluble organics can be attained with a higher sludge recirculation ratio. However, then the process becomes similar to a completely mixed reactor (Gujer and Jenkins, 1975).Figure 5.

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.