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Removal processes in sewage treatment plants: Sludge quality and treatment efficiency of structurally diverse organic compounds
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Large and ever-increasing numbers of chemicals, including large quantities of a broad spectrum of organic compounds are used in modern society. More than 30 000 of the more than 100 000 chemical substances registered in the EU are estimated to be daily used, of which many will be discharged into the waste-streams handled by municipal sewage treatment plants (STPs). The main objective of the work underlying this thesis was to improve understanding of the relationships between the characteristics of sewage contaminants and their sewage treatment efficiency. Further objectives were to examine the relationships between socio-economic uses of chemicals and sludge quality, and the effects of regulatory actions on sludge quality.

The quality of the sewage sludge and the levels and distribution patterns of the sludge contaminants, both within and between the STPs, seem to remain quite constant over time. The overall findings indicate that the levels of contaminants in sewage sludge seem to be largely independent of the location, size and treatment techniques applied at the STPs, and generally, of the types of human activity connected to them. The total and relative concentrations of the sludge contaminants were found to be fairly constant on a dry weight basis, with some exceptions, indicating that the pollutants originate from broad usage and diffuse dispersion rather than (industrial) point sources. The proportion of cyclic methylsiloxanes recovered in sludge seems to strongly depend on their vapour pressure, which decreases with the number of siloxane units. The higher water solubility and biodegradability of organophosphorus flame retardants and plasticizers than polybrominated diphenyl ethers (PBDEs) were also reflected in lower percentages (relative to their national use) found in sludge.

Significant time-trends in levels of a-third of the sludge contaminants included in the annual national measurement program were detected over a period of seven years. The levels of compounds displaying significant time-trends generally decreased following declines in the quantities used nationally. However, a quarter of these compounds showed increasing trends, of which the linear methylsiloxanes followed the same trend as used quantities. The decaBDE was also found to be increasing in sludge, probably as a result of the phase-out of pentaBDE and octaBDE.

The results indicate that the STP removal efficiency of anthropogenic substances, in Sweden, is generally good and that STPs, at least those in cold climates, do not efficiently remove certain polar contaminants. A non-targeted screening (by use of environmetrics and GCxGC-TOFMS) was performed and found to fulfil the objective to assess the STP removal efficiency, with emphasis to systematically analyse which compound classes that are not efficiently removed using the current STP technology. Many polar aromatic compounds were identified to be poorly removed.

The acquired data on levels, profiles and variations in sludge contaminants (sludge quality) extend both the available information and understanding of the degree and nature of sludge contamination, which should help attempts to track changes in its contaminants and revisions, if necessary, of guideline values. This thesis also contributes to improve the knowledge base for the development of future STP technologies, and that archived sewage sludge can be used in retrospective analysis of new and emerging pollutants.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2012. , 90 p.
Keyword [en]
Environmetrics, flame retardants, GCxGC, non-targeted screening, mass flow, metals, plasticizers, poorly removed contaminants, POP, PPCP, prediction, Principal Component Analysis, removal efficiency, sewage, sewage treatment plants, sludge, sludge adsorption, sources, time-trend analysis
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:umu:diva-51315ISBN: 978-91-7459-356-3 (print)OAI: oai:DiVA.org:umu-51315DiVA: diva2:479042
Public defence
2012-02-10, Naturvetarhuset, Hörsal N320, Umeå universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2012-01-20 Created: 2012-01-17 Last updated: 2012-01-18Bibliographically approved
List of papers
1. Behavior of fluoroquinolones and trimethoprim during mechanical, chemical, and active sludge treatment of sewage water and digestion of sludge
Open this publication in new window or tab >>Behavior of fluoroquinolones and trimethoprim during mechanical, chemical, and active sludge treatment of sewage water and digestion of sludge
Show others...
2006 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 40, no 3, 1042-1048 p.Article in journal (Refereed) Published
Abstract [en]

The behavior and fate of three fluoroquinolones (norfloxacin, ofloxacin, and ciprofloxacin), one sulfonamide (sulfamethoxazole), and trimethoprim were investigated at a sewage treatment plant in Umeå, Sweden, in 2004. This plant uses conventional mechanical, chemical, and activated sludge methods to treat the sewage water and digest the sludge; the dewatered digested sludge is pelleted (dry weight > 90% of total weight). Raw sewage water and particles as well as effluents and sludge from specific treatment areas within the plant were sampled. In addition to quantifying the antibiotics within the plant, we characterized the sample matrixes to facilitate evaluation of the results. Of the five substances examined, only norfloxacin, ciprofloxacin, and trimethoprim were present in concentrations higher than their limits of quantification. Norfloxacin and ciprofloxacin sorbed to sludge in a manner that was independent of changes in pH during sewage treatment, and more than 70% of the total amount of these compounds passing through the plant was ultimately found in the digested sludge. The results suggest that fluoroquinolones undergo thermal degradation during pelleting, but more studies are needed to confirm this. Trimethoprim was found in the final effluent at approximately the same concentration and mass flow as in the raw sewage, and could not be quantified in any solid sample. Predicted environmental concentrations, based on consumption data for Umeå municipality, correlated well with the results obtained, especially when the predicted concentrations were corrected to account for the amount of each active substance excreted in urine. The results obtained were compared to those of previous studies of these three substances' behavior and fate and were found to be similar, although some of the other plants studied employed the various treatment steps in different orders.

Place, publisher, year, edition, pages
Washington: American Chemical Society, 2006
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-5050 (URN)10.1021/es0516211 (DOI)
Available from: 2006-04-07 Created: 2006-04-07 Last updated: 2017-12-14Bibliographically approved
2. Behavior and fate of anthropogenic substances at a Swedish sewage treatment plant
Open this publication in new window or tab >>Behavior and fate of anthropogenic substances at a Swedish sewage treatment plant
2010 (English)In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 62, no 12, 2880-2888 p.Article in journal (Refereed) Published
Abstract [en]

The behavior and fate of anthropogenic substances during sewage treatment were investigated at a sewage treatment plant (STP) in Sweden which uses mechanical, chemical, and biological methods for sewage treatment and anaerobic digestion of sludge. Influent and effluent water, and sludge from two specific treatment sites were sampled. Mass balances were calculated from measured concentrations of various substances and estimates of the mass flows (water, solids) throughout the process. The results show that the metals (As, Cd, Cr, Hg, Pb) and the majority of PCBs, PCDD/Fs, and PBDEs enter and leave the STP bound to particles. Triclosan and di-(2-ethylhexyl)phthalate adsorb to sludge to a high degree, while the metals (Co, Cu, Ni, Zn) and organophosphate esters seem to pass through the STP unaffected by the process. Generally, the STP was better in removing lipophilic than water soluble compounds. Most of the substances end up in anaerobically digested sludge in almost the same concentrations as in primary sludge. A fugacity based STP model was evaluated for its ability to predict the behavior and fate of the substances and was found feasible for lipophilic compounds. It did however produce poor predictions for water soluble compounds such as organophosphate esters (overestimated) and antibacterial agents (underestimated).

Place, publisher, year, edition, pages
IWA Publishing, 2010
Keyword
cold climate STP, emerging pollutants, mass balances, POP, PPCP, sewage water and sludge
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-38683 (URN)10.2166/wst.2010.987 (DOI)000285237600019 ()21123918 (PubMedID)
Available from: 2010-12-21 Created: 2010-12-21 Last updated: 2017-12-11Bibliographically approved
3. Comprehensive mass flow analysis of Swedish sludge contaminants
Open this publication in new window or tab >>Comprehensive mass flow analysis of Swedish sludge contaminants
2013 (English)In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 90, no 1, 28-35 p.Article in journal (Refereed) Published
Abstract [en]

A screening of metals, persistent organic pollutants, pharmaceuticals and personal care products (PPCPs), and other organic contaminants in sludge from seven Swedish sewage treatment plants (STPs) was performed in this study. This extensive screening provides information on mass flows of 282 compounds used in the Swedish society to sewage sludge. It reveals constant relative contaminant concentrations (ng-mg kg-1 d.w.), except for some pesticides and perfluorinated compounds, indicating that these originate from broad usage and diffuse dispersion rather than (industrial) point sources. There was a five order of magnitude difference in the sum concentrations of the most and least abundant species (metals and polychlorinated dibenzo-p-dioxins and -furans, respectively). Lower total concentrations were found in sludge from STPs processing primarily food industry or household sewage. Proportions of the amounts used (in Sweden) found in sludge were lower for compounds that are present in consumer goods or are diffusely dispersed into the environment (0.01‑1% recovered in sludge) than for compounds used as detergents or PPCPs (17-63%). In some cases, the recovery seemed to be affected by evaporation (e.g. octamethyl-cyclotetrasiloxane) or biotransformation (e.g. adipates) losses, while polychlorinated alkanes and brominated diphenyl ethers were recovered to disproportionately high degree (ca.4%); likely due to incomplete statistics for imported goods.

Place, publisher, year, edition, pages
Elsevier, 2013
Keyword
PPCP, POP, Sewage sludge, Emerging pollutants
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-51313 (URN)10.1016/j.chemosphere.2012.07.002 (DOI)
Available from: 2012-01-17 Created: 2012-01-17 Last updated: 2017-12-08Bibliographically approved
4. Time-trends of metals and organic contaminants in sewage sludge
Open this publication in new window or tab >>Time-trends of metals and organic contaminants in sewage sludge
2012 (English)In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 46, no 15, 4841-4851 p.Article in journal (Refereed) Published
Abstract [en]

The occurrence of chemicals in sludge from sewage treatment plants (STPs) is of concern for human health and the environment, especially since STPs are considered to be major secondary sources of many toxic chemicals into the environment. Land application of sewage sludge is an attractive option for sludge management, as it consists of nutrients and organic matter. However, before sludge can be used for this purpose, the content of hazardous substances needs to be reduced to levels considered safe. Legislations and regulations are put in place to minimize the release of harmful chemicals into the environment, e.g. via sewage sludge. Temporal trends analysis of sludge contaminants can be used to assess the effectiveness of such actions. Such analyses can be performed retrospectively, using sludge stored in environmental specimen banks, to investigate new or emerging environmental contaminants. The present study provides data from time-trend analyses of metals, persistent organic pollutants, pharmaceuticals, personal care products, and other organic compounds in sludge from Swedish STPs (based on seven years of measurements). The analysis showed that sludge is a suitable matrix for time-trend studies and it can take on average 12 years (range, 5-26 years) to track an annual change of ±10% (with a power of 80%). Statistically significant trends were found for 18 out of the 77 compounds subjected to analysis, of which 75% showed decreasing trends. Triclosan and the antibiotic norfloxacin followed the same trend as the national recorded usage and decreased annually by 65% and 60%, respectively. The opposite was true for the methylsiloxanes, which showed an annual average increase of about 30%. A downward trend (about 20% year−1) was observed for the polybrominated diphenylethers (PBDEs 154 and 183), while PBDE 209 increased by 16%. Further measurements are required to determine if the substitution of PBDEs by chlorinated paraffins or organophosphorus compounds have resulted in increased concentrations of the latter in sludge.

Place, publisher, year, edition, pages
Elsevier, 2012
Keyword
Emerging pollutants, Organotin compounds, Organophosphorus compounds, POP, PPCP
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-51312 (URN)10.1016/j.watres.2012.05.048 (DOI)
Available from: 2012-01-17 Created: 2012-01-17 Last updated: 2017-12-08Bibliographically approved
5. Use of non-targeted environmetrics and comprehensive two-dimensional gas chromatography to assess sewage treatment plant removal efficiencies of structurally diverse organic contaminants
Open this publication in new window or tab >>Use of non-targeted environmetrics and comprehensive two-dimensional gas chromatography to assess sewage treatment plant removal efficiencies of structurally diverse organic contaminants
(English)Manuscript (preprint) (Other academic)
Abstract [en]

This study provides a new tool for the systematic and comprehensive screening of chemicals present in sewage and simultaneous assessment of sewage treatment plant (STP) removal efficiencies. Flow proportional samples were collected from a Swedish municipal STP, subjected to non-discriminating extraction and clean-up, and analyzed by comprehensive two-dimensional gas chromatography mass spectrometry (GCxGC-MS). Comparative environmetrics were used for outlier screening and removal efficiency assessment. The overall removal efficiency was good, but about 200 compounds were poorly extracted (<65%), of which 68 were tentatively identified based on their mass spectra and GC retention behavior. Most of the poorly extracted compounds were found in the aqueous phase of the effluent, with concentrations ranging from 0.2 to 12 000 ng L-1. Two amides (carbamazepine and diethyltoluamide (DEET)) were completely dissolved and not removed at all during treatment. Most of the compounds were aromatic (68%) or S,N,O-heterocyclic (31%) and chemically rather stable. All the compounds contained polar functional groups or moieties, which increase their water solubility and make them more prone to pass the STP unaffected. The new approach was used to identify new and emerging compounds, and generate information that could be used to improve current or design new STP treatment technologies.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-51311 (URN)
Available from: 2012-01-17 Created: 2012-01-17 Last updated: 2012-01-18Bibliographically approved

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