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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 wastewater treatment plant with recirculation of waste activated sludge to the primary settlers.
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f0004: Schematic of a wastewater treatment plant with recirculation of waste activated sludge to the primary settlers.

Mentions: Returning waste activated sludge (WAS) (Figure 4) to the primary settlers is a quite common practice in treatment plants (Tchobanoglous et al., 2004) and was used already in 1928 at the activated sludge plant in Essen-Relinghausen, Germany (Imhoff, 1951). Returning WAS to the primary settlers can improve the thickening properties of the secondary sludge which typically has a lower solids concentration than primary sludge (Tchobanoglous et al., 2004). Sorption onto the activated sludge can also contribute to the removal of organics in the primary settlers. Yetis and Tarlan (2002) investigated the effect of activated sludge addition on suspended solids removal during sedimentation of wastewater. The residual suspended solids concentration decreased from about 160 mg/L without activated sludge addition to about 50 mg/L with addition of 10% sludge by volume. The best results were obtained using sludge from a reactor operated at an SRT of 8–10 days and a sludge concentration above about 1600 mg/L in the sludge–wastewater mixture (Yetis and Tarlan, 2002). Ross and Crawford (1985) performed tests on two full-scale primary settlers, one was receiving WAS and the other was used as control. The WAS flow rate represented only 1.2% of the total flow to the settler and resulted in about 135 mg/L of sludge in the WAS-wastewater mixture. The effluent from the settler receiving WAS has slightly higher suspended solids concentration and slightly lower BOD and TOC concentration. However, only the difference in suspended solids concentration was statistically significant (Ross and Crawford, 1985).Figure 4.


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 wastewater treatment plant with recirculation of waste activated sludge to the primary settlers.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f0004: Schematic of a wastewater treatment plant with recirculation of waste activated sludge to the primary settlers.
Mentions: Returning waste activated sludge (WAS) (Figure 4) to the primary settlers is a quite common practice in treatment plants (Tchobanoglous et al., 2004) and was used already in 1928 at the activated sludge plant in Essen-Relinghausen, Germany (Imhoff, 1951). Returning WAS to the primary settlers can improve the thickening properties of the secondary sludge which typically has a lower solids concentration than primary sludge (Tchobanoglous et al., 2004). Sorption onto the activated sludge can also contribute to the removal of organics in the primary settlers. Yetis and Tarlan (2002) investigated the effect of activated sludge addition on suspended solids removal during sedimentation of wastewater. The residual suspended solids concentration decreased from about 160 mg/L without activated sludge addition to about 50 mg/L with addition of 10% sludge by volume. The best results were obtained using sludge from a reactor operated at an SRT of 8–10 days and a sludge concentration above about 1600 mg/L in the sludge–wastewater mixture (Yetis and Tarlan, 2002). Ross and Crawford (1985) performed tests on two full-scale primary settlers, one was receiving WAS and the other was used as control. The WAS flow rate represented only 1.2% of the total flow to the settler and resulted in about 135 mg/L of sludge in the WAS-wastewater mixture. The effluent from the settler receiving WAS has slightly higher suspended solids concentration and slightly lower BOD and TOC concentration. However, only the difference in suspended solids concentration was statistically significant (Ross and Crawford, 1985).Figure 4.

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.