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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 (Control), anaerobic digester sludge (ADS) and primary sludge (PS) of different concentrations.The original TOC concentrations and absorbance values before sedimentation are also shown. Averages of duplicate measurements are shown with the error bars representing the individual measurements. An asterisk (*) above a column indicate that the removal efficiency was significantly different (p<0.05, n = 2) from the control.
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pone.0119371.g001: Absorbance at 650 nm and 254 nm and concentrations of TOCp and TOCd in the mixtures of wastewater with effluent (Control), anaerobic digester sludge (ADS) and primary sludge (PS) of different concentrations.The original TOC concentrations and absorbance values before sedimentation are also shown. Averages of duplicate measurements are shown with the error bars representing the individual measurements. An asterisk (*) above a column indicate that the removal efficiency was significantly different (p<0.05, n = 2) from the control.

Mentions: The original concentrations of particulate and dissolved organics and the final concentration after 5 min mixing and 30 min sedimentation in controls and tests with addition of primary- and anaerobic sludge are shown in Fig. 1. Tests with addition of primary sludge and anaerobic digester sludge showed a net release of organic compounds from the sludge into the wastewater. Compared to the controls, both anaerobic digester sludge and primary sludge released particles into the wastewater, which can be seen by the increase in ABS650 and TOCp values. The amount of released TOCp was related to the amount of added sludge. For anaerobic digester sludge it was 45.3–49.5 mgTOCp/gVSS, whereas primary sludge released 21.7–27.8 mgTOCp/gVSS. For dissolved substances, anaerobic digester sludge released 4.3–6.3 mgTOCd/gVSS, whereas primary sludge did not have a net release of TOCd. However, the ABS254 and consequently the SUVA increased with both sludges. This indicates that aromatic organics, such as humic acids, were released by the sludge. In the primary sludge, this release was balanced by an uptake of other organics resulting in no net change in the TOCd concentration.


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 (Control), anaerobic digester sludge (ADS) and primary sludge (PS) of different concentrations.The original TOC concentrations and absorbance values before sedimentation are also shown. Averages of duplicate measurements are shown with the error bars representing the individual measurements. An asterisk (*) above a column indicate that the removal efficiency was significantly different (p<0.05, n = 2) from the control.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0119371.g001: Absorbance at 650 nm and 254 nm and concentrations of TOCp and TOCd in the mixtures of wastewater with effluent (Control), anaerobic digester sludge (ADS) and primary sludge (PS) of different concentrations.The original TOC concentrations and absorbance values before sedimentation are also shown. Averages of duplicate measurements are shown with the error bars representing the individual measurements. An asterisk (*) above a column indicate that the removal efficiency was significantly different (p<0.05, n = 2) from the control.
Mentions: The original concentrations of particulate and dissolved organics and the final concentration after 5 min mixing and 30 min sedimentation in controls and tests with addition of primary- and anaerobic sludge are shown in Fig. 1. Tests with addition of primary sludge and anaerobic digester sludge showed a net release of organic compounds from the sludge into the wastewater. Compared to the controls, both anaerobic digester sludge and primary sludge released particles into the wastewater, which can be seen by the increase in ABS650 and TOCp values. The amount of released TOCp was related to the amount of added sludge. For anaerobic digester sludge it was 45.3–49.5 mgTOCp/gVSS, whereas primary sludge released 21.7–27.8 mgTOCp/gVSS. For dissolved substances, anaerobic digester sludge released 4.3–6.3 mgTOCd/gVSS, whereas primary sludge did not have a net release of TOCd. However, the ABS254 and consequently the SUVA increased with both sludges. This indicates that aromatic organics, such as humic acids, were released by the sludge. In the primary sludge, this release was balanced by an uptake of other organics resulting in no net change in the TOCd concentration.

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.