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Estimation of Water Sampling Rates and Concentrations of PAHs in a Municipal Sewage Treatment Plant Using SPMDs with Performance Reference Compounds
Umeå University, Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Science and Technology, Chemistry.
2007 (English)In: Environmental Science and Technology, ISSN 0013-936X, Vol. 41, no 14, 5044-5049 p.Article in journal (Refereed) Published
Abstract [en]

Semipermeable membrane devices (SPMDs) were exposed at ten sampling points, each representing a different stage in the treatment process, in a municipal sewage treatment plant. Differences in SPMD uptake kinetics of polycyclic aromatic hydrocarbons (PAHs) due to variations in conditions at the sampling sites were evaluated by using five performance reference compounds (PRCs) with log Kow values of 4.20 to 6.34. PRC release rate constants (ke,PRC values) were calculated for PRCs for which 50-98% of the initial amounts were lost during the sampling period. The ke,PRC values were high, ranging from 0.08 to 0.11 day-1 for the studied PRCs, at sampling site W1 (raw sewage), the only sampling site where significant amounts of the PRCs with log Kow values >5 were released from the SPMDs. At the other sampling sites, only PRCs with log Kow values between 4.20 and 4.50 were released in significant amounts. The release rates at these sites were lowest (0.04 day-1) at sampling site W9 (the secondary clarifier) and highest (0.18 day-1) at W8 (the active sludge aeration basin). Differences between sampling rates (Rs) obtained using published laboratory-calibrated data and PRC-corrected Rs values were visualized by principal component analysis (PCA). The water concentrations of 24 studied PAHs fell substantially during the course of the sewage treatment process. However, low molecular weight PAHs were more effectively removed than high molecular weight PAHs. Significant deviations between actual and estimated water concentrations may arise unless PRC-corrected Rs values are applied.

Place, publisher, year, edition, pages
2007. Vol. 41, no 14, 5044-5049 p.
URN: urn:nbn:se:umu:diva-16041DOI: doi:10.1021/es070054+OAI: diva2:155714
Available from: 2007-08-16 Created: 2007-08-16Bibliographically approved
In thesis
1. Use and Development of Diffusive Samplers to Analyse the Fate of Polycyclic Aromatic Compounds, Polychlorinated Biphenyls and Pharmaceuticals in Wastewater Treatment Processes
Open this publication in new window or tab >>Use and Development of Diffusive Samplers to Analyse the Fate of Polycyclic Aromatic Compounds, Polychlorinated Biphenyls and Pharmaceuticals in Wastewater Treatment Processes
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The efficiency of wastewater treatment systems is commonly measured by the reductions of parameters such as biological oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS) and/or reductions in levels of selected macro compounds (e.g. long-chained hydrocarbons and inorganic compounds). Less attention has generally been paid to micropollutants with high potential toxic effects, such as polycyclic aromatic compounds (PACs), including unsubstituted and alkylated polycyclic aromatic hydrocarbons (PAHs) and dibenzothiophenes, polychlorinated biphenyls (PCBs), human pharmaceuticals and by-products formed during the treatment process. These organic micropollutants occur in wastewaters at trace and ultra-trace levels, therefore their detection requires advanced, costly analyses and large sample volumes. Furthermore, concentrations of micropollutants can fluctuate widely both diurnally and between days. Thus, in order to understand the fate of micropollutants in wastewaters there is a need to develop sampling techniques that allow representative samples to be readily collected.

In the work underlying this thesis two types of diffusive passive samplers, semipermeable membrane devices (SPMDs) and polar organic chemical integrative samplers (POCISs), were used to monitor non-polar and polar organic micropollutants in wastewaters subjected to various treatment processes. The pollutants sequestered in these samplers represent micropollutants in the dissolved phase that are available for aquatic organisms. Further, since they collect pollutants in an integrative manner, i.e. they sample continuously during the selected exposure time (usually approx. one to ca. three weeks), the results provide time-weighted average (TWA) concentrations. In addition, the effects of various environmental factors on the uptake of analyzed micropollutants in POCISs and SPMDs were investigated using laboratory calibration and in situ calibration with performance reference compounds (PRCs).

The results confirm that SPMDs are good sampling tools for investigating the efficacy of wastewater treatment processes for removing non-polar PACs and PCBs, and the effects of varying the process settings. In addition, analyses of process streams in municipal sewage treatment plants demonstrated that conventional sewage treatment processes are not optimized for removing dissolved four-ringed PAHs, some of the five-ringed PAHs, and tri- to hexa-chlorinated biphenyls. The removal of bioavailable PACs was enhanced by adding sorbents with high sorption capacities to the sludge used in the activated sludge treatment step, and a biologically activated carbon system was designed that robustly removed bioavailable PACs, with removal efficiencies of 96.9-99.7 percent across the tested ranges of five varied process parameters.

In situ SPMD calibration data acquired show that uptake of PACs, described by SPMD sampling rates (Rs), were four to eight times higher than published laboratory calibrated Rs values, mainly due to strong (bio)fouling and turbulence effects. In addition, the laboratory calibration study demonstrated that temperature affects the POCIS uptake of pharmaceuticals. The uptake of four pharmaceuticals was higher, by 10-56 percent, at 18 °C compared to 5 °C. For two of the pharmaceuticals our data indicate that the uptake was lower by 18-25 percent at 18 °C. Our results also indicate that uptake of the studied pharmaceuticals was in the linear phase throughout the 35 day exposure period at both temperatures. Finally, calibration studies enabled aqueous concentrations of micropollutants to be more accurately estimated from amounts collected in the passive samplers.

Place, publisher, year, edition, pages
Umeå: Kemi, 2008. 49 p.
bioavailable, biologically activated carbon, PRCs, sampling rate, SPMD, sorption, wastewater treatment, diffusive passive samplers, human pharmaceuticals, municipal sewage treatment plant, organic micropollutants, polycyclic aromatic compounds, PAHs, PCBs, POCIS
National Category
Environmental Sciences
urn:nbn:se:umu:diva-1912 (URN)978-91-7264-688-9 (ISBN)
Public defence
2008-12-05, KB3A9, KBC, Umeå, 10:00 (English)
Available from: 2008-11-10 Created: 2008-11-10 Last updated: 2009-06-18Bibliographically approved

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