Limits...
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 wastewater treatment plant with lipid enhancement of waste sludge (adapted from Mondala et al. (2012) and Revellame et al. (2013)).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4940897&req=5

f0009: Schematic of wastewater treatment plant with lipid enhancement of waste sludge (adapted from Mondala et al. (2012) and Revellame et al. (2013)).

Mentions: Biodiesel consists of fatty acid alkyl esters, for example fatty acid methyl ester (FAME). Direct production of FAME from activated sludge has been investigated in several studies. The lipid component of the sludge undergoes an acid-catalyzed transesterification reaction with methanol resulting in FAME, which can be extracted from the liquid using, e.g., hexane. Yields of about 2.5–6.2% (FAME per dry weight of sludge) have been obtained using waste activated sludge samples (Dufreche et al., 2007; Mondala et al., 2009; Revellame et al., 2010; Revellame et al., 2011). Dufreche et al. (2007) estimated that a yield of about 10% would be needed for sludge biodiesel to be economically competitive with soy-based biodiesel. TAG is an excellent feedstock for biodiesel. In order to increase the TAG content of the sludge, feeding waste activated sludge with a carbohydrate solution has been investigated (Mondala et al., 2012; Mondala et al., 2013; Revellame et al., 2013). Mondala et al. (2012) obtained a biodiesel yield of 10.2% by feeding the sludge with 60 g/L glucose. An activated sludge process solution for generating sludge with enhanced lipid content as proposed by Mondala et al. (2012) and Revellame et al. (2013) is shown in Figure 9. Another strategy was used by Hall et al. (2011) who augmented wastewater with oleaginous microorganisms. However, the results did not show that the added microorganisms could compete with the indigenous microbial population over time. As mentioned in Section 7.2, PHA can also be used to produce biofuels (Muller et al., 2014). Esterification of PHA yields hydroxyalkanoate methyl esters. Wang et al. (2010) showed that 3-hydroxybutyrate methyl ester produced from PHB had similar or better properties than ethanol when used as an additive in gasoline.Figure 9.


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 wastewater treatment plant with lipid enhancement of waste sludge (adapted from Mondala et al. (2012) and Revellame et al. (2013)).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f0009: Schematic of wastewater treatment plant with lipid enhancement of waste sludge (adapted from Mondala et al. (2012) and Revellame et al. (2013)).
Mentions: Biodiesel consists of fatty acid alkyl esters, for example fatty acid methyl ester (FAME). Direct production of FAME from activated sludge has been investigated in several studies. The lipid component of the sludge undergoes an acid-catalyzed transesterification reaction with methanol resulting in FAME, which can be extracted from the liquid using, e.g., hexane. Yields of about 2.5–6.2% (FAME per dry weight of sludge) have been obtained using waste activated sludge samples (Dufreche et al., 2007; Mondala et al., 2009; Revellame et al., 2010; Revellame et al., 2011). Dufreche et al. (2007) estimated that a yield of about 10% would be needed for sludge biodiesel to be economically competitive with soy-based biodiesel. TAG is an excellent feedstock for biodiesel. In order to increase the TAG content of the sludge, feeding waste activated sludge with a carbohydrate solution has been investigated (Mondala et al., 2012; Mondala et al., 2013; Revellame et al., 2013). Mondala et al. (2012) obtained a biodiesel yield of 10.2% by feeding the sludge with 60 g/L glucose. An activated sludge process solution for generating sludge with enhanced lipid content as proposed by Mondala et al. (2012) and Revellame et al. (2013) is shown in Figure 9. Another strategy was used by Hall et al. (2011) who augmented wastewater with oleaginous microorganisms. However, the results did not show that the added microorganisms could compete with the indigenous microbial population over time. As mentioned in Section 7.2, PHA can also be used to produce biofuels (Muller et al., 2014). Esterification of PHA yields hydroxyalkanoate methyl esters. Wang et al. (2010) showed that 3-hydroxybutyrate methyl ester produced from PHB had similar or better properties than ethanol when used as an additive in gasoline.Figure 9.

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.