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Time-trends of metals and organic contaminants in sewage sludge
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Swedish Museum of Natural History.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
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. Vol. 46, no 15, 4841-4851 p.
Keyword [en]
Emerging pollutants, Organotin compounds, Organophosphorus compounds, POP, PPCP
National Category
Chemical Sciences
URN: urn:nbn:se:umu:diva-51312DOI: 10.1016/j.watres.2012.05.048OAI: diva2:478985
Available from: 2012-01-17 Created: 2012-01-17 Last updated: 2012-10-16Bibliographically approved
In thesis
1. Removal processes in sewage treatment plants: Sludge quality and treatment efficiency of structurally diverse organic compounds
Open this publication in new window or tab >>Removal processes in sewage treatment plants: Sludge quality and treatment efficiency of structurally diverse organic compounds
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.
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
urn:nbn:se:umu:diva-51315 (URN)978-91-7459-356-3 (ISBN)
Public defence
2012-02-10, Naturvetarhuset, Hörsal N320, Umeå universitet, Umeå, 10:00 (English)
Available from: 2012-01-20 Created: 2012-01-17 Last updated: 2012-01-18Bibliographically approved

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Olofsson, UlrikaHaglund, Peter
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