| 1. |
- Andersson, Anna, et al.
(författare)
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Molecular changes among non-volatile disinfection by-products between drinking water treatment and consumer taps
- 2021
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Ingår i: Environmental Science. - : Royal Society of Chemistry. - 2053-1400 .- 2053-1419. ; 7:12, s. 2335-2345
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Tidskriftsartikel (refereegranskat)abstract
- The formation of disinfection by-products (DBPs) during drinking water treatment has been associated with various health concerns but the total DBP exposure is still unknown. In this study, molecular level non-target analysis by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to study non-volatile DBPs, and how their composition changes during water distribution in four drinking water treatment plants (DWTPs) in Sweden using different types of raw water and disinfection processes. The largest portion of tap water DBP compositions were detected also at the DWTPs, highlighting that these DBP formulae were rather stable and contribute to human DBP exposure. Yet the number of detected DBPs decreased 14-48% between drinking water treatment and consumer taps in the three plants in which no mixing of water from other DWTPs in the distribution system occurred showing active DBP processing in the water distribution network. While considerable amounts of bromine-containing DBPs were detected upon chemical disinfection in some DWTPs, few of them were detected in the tap water samples, likely due to debromination by hydrolytic reactions. The overall fewer non-volatile DBPs detected in tap waters, along with changed distribution among chlorine and bromine DBPs, demonstrate that DBP mixtures are highly dynamic and that DBP measurements at DWTPs do not adequately reflect exposure at the point-of-use. Clearly, more knowledge about changes of DBP mixtures through the distribution system is needed to improve DBP exposure assessments.
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| 2. |
- Hägg, Kristofer, et al.
(författare)
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Water quality changes during the first meter of managed aquifer recharge
- 2021
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Ingår i: Environmental Science: Water Research and Technology. - : Royal Society of Chemistry (RSC). - 2053-1419 .- 2053-1400. ; 7:3, s. 562-572
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Tidskriftsartikel (refereegranskat)abstract
- The capacity of an artificial recharge field to alter organic matter and the bacterial flora of surface water was assessed by following changes in bacterial communities and composition of natural organic matter (NOM) over the first meter of infiltration depth. The sampling strategy applied in this study ensured that water samples consisted only of infiltrated water, excluding natural groundwater. Water was sampled at 50 and 100 cm below the surface of an infiltration basin divided into two halves; one side was dried and frozen and one was infiltrating water during the winter period prior to the sampling period. Bacterial cell counts, proportions of intact cells and community fingerprints were determined by flow cytometry, and NOM was characterized using total organic carbon (TOC), UV254 nm-absorbance (UVA) and fluorescence spectroscopy. Around 40% of the NOM was removed after only 50 cm. Protein-like components were reduced to a larger extent (45-50%) than the humic-like components (25%), suggesting removal of mostly biodegradable fractions of NOM. After only 50 cm of infiltration, about 99% total cell count (TCC) was removed. The flow cytometric data revealed that the bacterial communities collected after infiltration from the basin area that had been dried and frozen were more similar to those in the raw water. This suggests that drying and freezing the basin negatively impacted its treatment capacity. The results from this study highlight the importance of a well-developed biofilm and unsaturated zone for artificial recharge.
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| 3. |
- Ullberg, Malin, et al.
(författare)
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Pilot-scale removal of organic micropollutants and natural organic matter from drinking water using ozonation followed by granular activated carbon
- 2021
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Ingår i: Environmental Science: Water Research & Technology. - : Royal Society of Chemistry (RSC). - 2053-1400 .- 2053-1419. ; 7, s. 535-548
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Tidskriftsartikel (refereegranskat)abstract
- Conventional drinking water treatment is inefficient in removing a large fraction of known organic micropollutants (OMPs). Therefore more efficient treatment approaches are needed to limit exposure to OMPs via drinking water. Here, the OMP removal performance of a combination of ozonation/no ozonation and two types of granular activated carbon (GAC) was tested in a one-year pilot-scale study, alongside a study of full-scale treatment. The raw water was lake water with low ambient concentrations of OMPs. In total, 29 of 99 targeted OMPs (per- and polyfluoroalkyl substances (PFASs), pharmaceuticals and other OMPs) were detected (mean n-ary sumation OMPs = 57 +/- 16 ng L-1). Only a few OMPs were consistently removed in the full-scale process, while ozonation in the pilot experiment effectively removed 72% of detected compounds to levels <30%. The GAC columns showed breakthrough of OMPs and dissolved organic carbon (DOC) for both ozonated and non-ozonated water, with earlier breakthrough for DOC than OMPs. Breakthrough of OMPs was delayed in ozonated columns, possibly because of lower adsorption competition with low-molecular-weight natural organic matter (NOM) fractions measured with liquid chromatography (LC-OCD). The OMP removal performance of the two GAC materials was not affected by greater DOC loading, but Filtrasorb showed 25% higher removal of DOC without losing capacity to remove OMPs. Compounds with low log K-OC tended to break through earlier than those with higher K-OC values. The lowest levels of OMPs were observed in GAC effluents using ozonated feed water demonstrating the efficacy of combining ozone with GAC for managing OMP levels during drinking water production.
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