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Sorption and release of organics by primary, anaerobic, and aerobic activated sludge mixed with raw municipal wastewater.

Modin O, Saheb Alam S, Persson F, Wilén BM - PLoS ONE (2015)

Bottom Line: This study compared primary-, anaerobic-, and aerobic activated sludge as sorbents, determined sorption capacity and kinetics, and investigated some characteristics of the organics being sorbed.The 5-min sorption capacity of activated sludge was 6.5±10.8 mg total organic carbon (TOC) per g volatile suspend solids (VSS) for particulate organics and 5.0±4.7 mgTOC/gVSS for dissolved organics.The observed instantaneous sorption appeared to be mainly due to organics larger than 20 kDa in size being sorbed, although molecules with a size of about 200 Da with strong UV absorbance at 215-230 nm were also rapidly removed.

View Article: PubMed Central - PubMed

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

ABSTRACT
New activated sludge processes that utilize sorption as a major mechanism for organics removal are being developed to maximize energy recovery from wastewater organics, or as enhanced primary treatment technologies. To model and optimize sorption-based activated sludge processes, further knowledge about sorption of organics onto sludge is needed. This study compared primary-, anaerobic-, and aerobic activated sludge as sorbents, determined sorption capacity and kinetics, and investigated some characteristics of the organics being sorbed. Batch sorption assays were carried out without aeration at a mixing velocity of 200 rpm. Only aerobic activated sludge showed net sorption of organics. Sorption of dissolved organics occurred by a near-instantaneous sorption event followed by a slower process that obeyed 1st order kinetics. Sorption of particulates also followed 1st order kinetics but there was no instantaneous sorption event; instead there was a release of particles upon mixing. The 5-min sorption capacity of activated sludge was 6.5±10.8 mg total organic carbon (TOC) per g volatile suspend solids (VSS) for particulate organics and 5.0±4.7 mgTOC/gVSS for dissolved organics. The observed instantaneous sorption appeared to be mainly due to organics larger than 20 kDa in size being sorbed, although molecules with a size of about 200 Da with strong UV absorbance at 215-230 nm were also rapidly removed.

No MeSH data available.


Absorbance at 650 nm and 254 nm and concentrations of TOCp and TOCd in the mixtures of wastewater with effluent or activated sludge suspension.Original refers to the concentrations before sedimentation. Control, low addition, and high addition refers to the concentration in the supernatant after 30 min sedimentation with zero (control), 0.30–0.39 gTSS/L (low addition), or 1.04–1.37 gTSS/L (high addition) activated sludge. Averages of duplicate measurements are shown with the error bars representing the individual measurements. ABS650 was not measured on sampling day 6.
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pone.0119371.g002: Absorbance at 650 nm and 254 nm and concentrations of TOCp and TOCd in the mixtures of wastewater with effluent or activated sludge suspension.Original refers to the concentrations before sedimentation. Control, low addition, and high addition refers to the concentration in the supernatant after 30 min sedimentation with zero (control), 0.30–0.39 gTSS/L (low addition), or 1.04–1.37 gTSS/L (high addition) activated sludge. Averages of duplicate measurements are shown with the error bars representing the individual measurements. ABS650 was not measured on sampling day 6.

Mentions: The change in TOCp and TOCd concentrations, ABS254 and ABS650 for the sorption tests carried out with aerobic activated sludge on seven different sampling days are shown in Fig. 2. The influent wastewater characteristics varied between the different sampling days, especially in terms of particulate content (see the original values of TOCp and ABS650 in Fig. 2). Addition of activated sludge generally appeared to have a small but positive impact on the net removal of both particulate (TOCp and ABS650) and dissolved (TOCd and ABS254) organic carbon. To verify that activated sludge addition did indeed have an effect on the removal, statistical analysis was carried out (Table 1). For the parameters ABS650, TOCp, ABS254, and TOCd addition of both low and high concentration of activated sludge always resulted in a statistically significant difference in removal efficiency compared to the controls suggesting that addition of activated sludge could improve removal of both particulate and dissolved substances. For all parameters except ABS650, there was also a significant difference in the removal between low (0.30–0.39 gTSS/L) and high (1.04–1.37 gTSS/L) activated sludge addition (Table 1). The average sorption of TOCp was 6.5±10.8 mgTOCp/gVSS while the sorption of TOCd was 5.0±4.7 mgTOCd/gVSS. Thus, the total organics sorption was 11.5±11.8 mgTOC/gVSS. There was no difference in the SUVA between the controls and the samples with sludge addition suggesting that the aromatic content of the wastewater organics did not change because of mixing with activated sludge.


Sorption and release of organics by primary, anaerobic, and aerobic activated sludge mixed with raw municipal wastewater.

Modin O, Saheb Alam S, Persson F, Wilén BM - PLoS ONE (2015)

Absorbance at 650 nm and 254 nm and concentrations of TOCp and TOCd in the mixtures of wastewater with effluent or activated sludge suspension.Original refers to the concentrations before sedimentation. Control, low addition, and high addition refers to the concentration in the supernatant after 30 min sedimentation with zero (control), 0.30–0.39 gTSS/L (low addition), or 1.04–1.37 gTSS/L (high addition) activated sludge. Averages of duplicate measurements are shown with the error bars representing the individual measurements. ABS650 was not measured on sampling day 6.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4359093&req=5

pone.0119371.g002: Absorbance at 650 nm and 254 nm and concentrations of TOCp and TOCd in the mixtures of wastewater with effluent or activated sludge suspension.Original refers to the concentrations before sedimentation. Control, low addition, and high addition refers to the concentration in the supernatant after 30 min sedimentation with zero (control), 0.30–0.39 gTSS/L (low addition), or 1.04–1.37 gTSS/L (high addition) activated sludge. Averages of duplicate measurements are shown with the error bars representing the individual measurements. ABS650 was not measured on sampling day 6.
Mentions: The change in TOCp and TOCd concentrations, ABS254 and ABS650 for the sorption tests carried out with aerobic activated sludge on seven different sampling days are shown in Fig. 2. The influent wastewater characteristics varied between the different sampling days, especially in terms of particulate content (see the original values of TOCp and ABS650 in Fig. 2). Addition of activated sludge generally appeared to have a small but positive impact on the net removal of both particulate (TOCp and ABS650) and dissolved (TOCd and ABS254) organic carbon. To verify that activated sludge addition did indeed have an effect on the removal, statistical analysis was carried out (Table 1). For the parameters ABS650, TOCp, ABS254, and TOCd addition of both low and high concentration of activated sludge always resulted in a statistically significant difference in removal efficiency compared to the controls suggesting that addition of activated sludge could improve removal of both particulate and dissolved substances. For all parameters except ABS650, there was also a significant difference in the removal between low (0.30–0.39 gTSS/L) and high (1.04–1.37 gTSS/L) activated sludge addition (Table 1). The average sorption of TOCp was 6.5±10.8 mgTOCp/gVSS while the sorption of TOCd was 5.0±4.7 mgTOCd/gVSS. Thus, the total organics sorption was 11.5±11.8 mgTOC/gVSS. There was no difference in the SUVA between the controls and the samples with sludge addition suggesting that the aromatic content of the wastewater organics did not change because of mixing with activated sludge.

Bottom Line: This study compared primary-, anaerobic-, and aerobic activated sludge as sorbents, determined sorption capacity and kinetics, and investigated some characteristics of the organics being sorbed.The 5-min sorption capacity of activated sludge was 6.5±10.8 mg total organic carbon (TOC) per g volatile suspend solids (VSS) for particulate organics and 5.0±4.7 mgTOC/gVSS for dissolved organics.The observed instantaneous sorption appeared to be mainly due to organics larger than 20 kDa in size being sorbed, although molecules with a size of about 200 Da with strong UV absorbance at 215-230 nm were also rapidly removed.

View Article: PubMed Central - PubMed

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

ABSTRACT
New activated sludge processes that utilize sorption as a major mechanism for organics removal are being developed to maximize energy recovery from wastewater organics, or as enhanced primary treatment technologies. To model and optimize sorption-based activated sludge processes, further knowledge about sorption of organics onto sludge is needed. This study compared primary-, anaerobic-, and aerobic activated sludge as sorbents, determined sorption capacity and kinetics, and investigated some characteristics of the organics being sorbed. Batch sorption assays were carried out without aeration at a mixing velocity of 200 rpm. Only aerobic activated sludge showed net sorption of organics. Sorption of dissolved organics occurred by a near-instantaneous sorption event followed by a slower process that obeyed 1st order kinetics. Sorption of particulates also followed 1st order kinetics but there was no instantaneous sorption event; instead there was a release of particles upon mixing. The 5-min sorption capacity of activated sludge was 6.5±10.8 mg total organic carbon (TOC) per g volatile suspend solids (VSS) for particulate organics and 5.0±4.7 mgTOC/gVSS for dissolved organics. The observed instantaneous sorption appeared to be mainly due to organics larger than 20 kDa in size being sorbed, although molecules with a size of about 200 Da with strong UV absorbance at 215-230 nm were also rapidly removed.

No MeSH data available.