| 1. |
- Andersson, Anna, et al.
(författare)
-
Selective removal of natural organic matter during drinking water production changes the composition of disinfection by-products
- 2020
-
Ingår i: Environmental Science. - : ROYAL SOC CHEMISTRY. - 2053-1400 .- 2053-1419. ; 6:3, s. 779-794
-
Tidskriftsartikel (refereegranskat)abstract
- Disinfection by-products (DBPs) are potentially toxic compounds formed upon chemical disinfection of drinking water. Controlling the levels and characteristics of dissolved organic matter (DOM) as precursor material for DBPs is a major target to reduce DBP formation. A pilot-scale treatment including suspended ion exchange (SIX (R)), a ceramic microfilter (CeraMac (R)) with in-line coagulation and optional pre-ozonation followed by granular activated carbon (GAC) filtration was compared with a conventional full-scale treatment based on DOM removal and DBP formation using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), rapid fractionation, liquid chromatography organic carbon detection (LC-OCD), adsorbable organic halogens (AOX) and trihalomethane (THM) analysis. The new treatment combination showed different selectivity for DOM removal, compared to the conventional, leading to changes in composition of the DBPs formed. SIX (R) and GAC had the largest impacts on reducing AOX and THM formation potentials but the high adsorptive capacity of GAC affected the diversity of detected DBPs most. Chlorination and chloramination of pilot treated water with doses normally used in Sweden produced low levels of AOX compared to the full-scale treatment, but FT-ICR MS revealed an abundance of brominated DBP species in contrast with the conventional treatment, which were dominated by chlorinated DBPs. This finding was largely linked to the high DOM removal by the pilot treatment, causing an increased Br-/C ratio and a higher formation of HOBr. Potential increases in Br-DBPs are important to consider in minimizing health risks associated with DBPs, because of the supposed higher toxicity of Br-DBPs compared to Cl-DBPs.
|
|
| 2. |
- Hoffmeister, Svenja, et al.
(författare)
-
Evaluating the accuracy of two in-situ optical sensors to estimate DOC concentrations for drinking water production
- 2020
-
Ingår i: Environmental Science: Water Research and Technology. - : Royal Society of Chemistry (RSC). - 2053-1419 .- 2053-1400. ; 6:10, s. 2891-2901
-
Tidskriftsartikel (refereegranskat)abstract
- Two in situ optical sensors, a single-excitation fluorescence-based sensor (fDOM) mounted on a multi-parameter EXO2 sonde (YSI), and a stand-alone, multispectral absorbance-based instrument (spectro::lyser, scan Messtechnik GmbH), were evaluated for their capability to (i) estimate river dissolved organic carbon (DOC) concentrations and (ii) provide oversight of drinking water production. The sensors were deployed between March and November 2017 in the river Fyris, which drains a mixed forested and agricultural 2003 km2 catchment and serves as a drinking water source by managed aquifer recharge. Grab samples were collected every 2 to 3 weeks and compared with logged sensor data collected at 15 minute intervals. The fDOM probe signal was used to estimate DOC concentrations in the range of 10.4 to 24.4 mg L−1 using linear regression (R2 = 0.71, RMSE = 2.5 mg L−1), after correction for temperature, turbidity and inner-filter effects. Temporal changes in DOC character associated with the mixed land use landscape, as indicated by optical indices, reduced this sensor accuracy for estimating DOC concentration. Nevertheless, humic substance concentrations, the fraction of DOC that is preferentially removed during artificial infiltration, were well captured. The spectrolyser signal was used to establish a 2-component partial least square model that captured DOC fluctuations from 10.2 to 29.4 mg L−1 (R2 = 0.92; RMSE = 1.3 mg L−1). This multiple-wavelength model (220 to 720 nm) effectively handled the changes in DOC composition while accurately estimating DOC concentrations. This study explores the advantages and limitations of optical sensors for their use in managed aquifer recharge and drinking water production in relation to DOC levels.
|
|
| 3. |
|
|
| 4. |
- Pullerits, Kristjan, et al.
(författare)
-
Impact of coagulation–ultrafiltration on long-term pipe biofilm dynamics in a full-scale chloraminated drinking water distribution system
- 2020
-
Ingår i: Environmental Science: Water Research & Technology. - 2053-1419. ; 6:11, s. 3044-3056
-
Tidskriftsartikel (refereegranskat)abstract
- While pipe biofilms in DWDSs (drinking water distribution systems) are thought to affect the quality of distributed water, studies regarding the microbial processes are impeded by the difficulties in accessing biofilm undisturbed by DWDS maintenance. In this study, pipe sections were removed from a fully operational DWDS for biofilm sampling over two years and three months, and before and after start of ultrafiltration (UF) with coagulation treatment in the drinking water treatment plant (DWTP). Water (n = 31), surface biofilm (obtained by swabbing, n = 34) and deep pipe biofilm (obtained by scraping, n = 34) were analyzed with 16S rRNA gene amplicon sequencing; with flow cytometry, and chemical and natural organic matter (NOM) analysis as additional parameters for water quality. UF with coagulation decreased the total cell concentration in the DWDS bulk water from 6.0 × 105 ± 2.3 × 105 cells per ml to 6.0 × 103 ± 8.3 × 103 cells per ml, including fluctuations due to seasonal change, as well as decreasing most analyzed fractions of NOM. UF treatment of the water revealed that 75% ± 18% of the cells in the water originated from DWDS biofilm, confirmed by SourceTracker analysis, with the rest of the cells likely released from biofilm on DWTP storage tanks. Following UF start, the ASVs (amplicon sequence variants) in the deep pipe biofilm decreased, and Evenness and Shannon diversity indices decreased, reflecting the community's response to the new environment created by the altered water quality. The pipe biofilm community was dominated by ASVs classified as Nitrosomonadaceae, Nitrospira, Hyphomicrobium and Sphingomonas, with relative abundances ranging from 5–78%, and also included ASVs of genus Mycobacterium, genus Legionella and order Legionellales. This community composition, together with the observation that turnover of nitrogen compounds was unchanged by UF start, indicate that nitrification in the DWDS was localized to the pipe biofilm.
|
|
