NOMiNOR: Natural Organic Matter (NOM) in Nordic drinking waters
Surface waters in Scotland, as well as in southern Norway and southern Sweden have experienced a significant increase in NOM-concentrations and fluctuations over the last decades, likely due to the combined effects of climate variation and reduced acid rain.
NOM concentration levels and physiochemical properties vary significantly in space and time. Especially the seasonal fluctuations are site specific and therefore unique to any raw water source.
Surface waters are commonly used as raw water sources by waterworks for tap-water production in these countries. NOM in the water affect colour, taste and odour. Increasing concentrations of NOM, thus, causes increased demand for coagulant and disinfectant doses. NOM influences, furthermore, the stability and thereby the removal of inorganic particles and pathogens and increase the mobility of micro-pollutants. It fouls membranes, block filtration pores and compete for adsorption sites. In the water distribution networks, NOM influences on corrosion and leads to regrowth and biofilm formation during distribution, including house installations (e.g. problems with biofilm-amoebae-Legionella).
The increasing amount and variability of NOM concentrations and characteristics, thus, represents severe challenges for process control in water treatment and distribution systems.
About the project
The physiochemical characteristics and concentration of NOM controls in many ways the selection of optimum water treatment technology, treatment process design and the operation performance of treatment plants and distribution systems. In addition to undesired colour, taste and odour of the tap water, elevated levels of NOM may produce disinfection by-products (DBP), associate with organic and inorganic pollutants.
Therefore, NOM characterization/NOM-diagnosis are valuable tools and prerequisites in order to adequately control NOM in tap water and un-wanted NOM-related effects. There exist a large number of analytical techniques that are being used to characterize NOM. Some of these methods are laborious and require advanced analytical equipment and are therefore less applicable for routine monitoring in the water plants – though these methods are valuable in science/academia in order to increase our understanding of NOM nature and fate during treatment and distribution. More readily applicable analytical methods are typically less specific but may provide valuable proxy for treatment and distribution-relevant characteristics of NOM. A goal is therefore to understand better and thereby improve our interpretation of these common proxies. A major shortcoming in the humic matter science is poor precision of the very operationally defined analytical methods. This is partly due to differing sample handling and preparation as well as methodological differences in sample condition and instrumentation settings.
The participation by the Environmental Analysis Group at UiO is mainly related to WP2
The major objective of the NOMiNOR project is to address and strengthen the conceptual understanding, linking raw water NOM characteristics to NOM control and NOM removal. This is a prerequisite to improve water treatment and distribution performance. Included in this is the objective of increasing the level of knowledge and competence on optimum NOM control during water treatment and distribution by the application of the same set of NOM-diagnostic tools (further described in Ch. 4) for monitoring as well as a comprehensive characterization of seasonal water samples collected during winter, spring, summer and autumn periods from water works in Sweden, Scotland and Norway.
Application of the same characterization tools analyzed using the same sample handling, treatment and analysis protocol allow direct comparisons between treatment results obtained at water works with different climate and source/watershed characteristics, different treatment technologies, different disinfection policies (e.g. chlorine free distribution or not), etc. Mapping of site-specific conditions on climate, vegetation, land use, geology and soil morphology in the watershed of the raw water will be used to unravel governing factors for temporal and spatial differences between the physiochemical characteristics of the NOM. This will be related to treatment plant and distribution system characteristics as well as site-specific operation conditions which are included in the activities. Thus the results are expected to contribute to valuable exchange of information, knowledge and competence among the participating waterworks and other stakeholders within the water industry.
Key questions to be addressed:
1) To what extent does climate change (temperature and runoff characteristics) explain changes in NOM levels and characteristics among different raw water sources, relative to other factors (changes in acid deposition and areal use)?
2) Can a hydrological water balance approach improve our understanding on the great spatial variations in concentration and properties of NOM? Based on this knowledge is it possible to evaluate: ?
a. How sensitive the different waterworks are to changes in weather conditions?
b. Which weather conditions represent special challenges to the waterworks with respect to NOM levels and properties?
3) Can the use of the suggested set of readily applicable NOM-characterization tools allow better predictions of: i) achieved and achievable (optimum) water quality and treatment results, and ii) challenges related to biological regrowth and biofilm formation, including interactions with and NOM-adsorption to metals precipitated on the pipe walls?
a. Can the applied NOM-characterization tools form a basis for the development of safer water supply systems and more resource-efficient NOM removal processes, i.e. better adaptation of treatment and treatment conditions to raw water (NOM) characteristics, watershed and distribution system characteristics?
b. Can the applied NOM-characterization tools also contribute to a better understanding and to improved operations of distribution systems, i.e. reduced corrosion, reduced biofilm formation/layers of precipitation, reduced sludge formation, reduced need for pipeline flushing?
4) What NOM-fractions are removed/not removed by different treatment technologies, e.g. enhanced coagulation, NF, ozonation-biological filtration (OBF), GAC, etc?
a. How are the bio-available NOM-fractions (BOM) and the biological stability in distributed water affected by different treatment and disinfection technologies?
5) Can the results be used to improve the basis for optimum treatment process and treatment train selection, optimum system design, optimum operation and retrofitting/upgrading of existing systems also with respect to safer, more sustainable and more climate-robust water supply systems?
6) Can this project through the use of common analytical tools, and thus directly comparable results, contribute to increased exchange of knowledge between waterworks and stakeholders?
7) Can a set of NOM-characterization methods be implemented as "standard" for the Nordic region?
Deliverables from NOMiNOR include:
1) Following each sampling/analysis round reports will be submitted to each waterworks presenting the data and their preliminary assessments
2) Project meetings (1-2 per years) with presentations and discussions of obtained results.
3) Internet project Homepage disseminating project findings to end-users
4) Research articles in peer review international scientific journals from post doc-studies at the Norwegian University of Life Sciences (UMB), University of Oslo (UiO) and Cranfield University (UCRAN).
5) Conference papers and journal articles, including presentations at seminars arranged by Norwegian Water/Swedish Water, etc
6) A final meeting with presentation and discussion of overall results, conclusions and implications
- WP1 Water sampling and NOM-analyses
- WP2 Watershed and water chemistry
- WP2 includes activities on characterization of watersheds, land-use, type and amount of vegetation, soil/geology, climatic conditions, precipitation patterns, hydrology, water chemistry, etc. UiO and UMB will share a post-doc candidate for this work. UiO will take on main responsibility for the activities related to water/water chemistry and UMB for mapping and characterization of the watersheds. Here, we will attempt to discern effects of acid rain from climate change and study processes governing NOM leaching
Task 2.1 Watershed characteristics: Watershed mapping (GIS) and water balance model. Linking of temporal variation in NOM to fluctuations in hydrology. Analysis of major anions, preparation of reports and publications.
Task 2.2 Water chemistry: Water chemistry analysis of Al, Fe fractions or alkalinity (200 samples). 10 Photo- and biodegradation assays in 2014 and 10 more samples in 2015, i.e. raw water and treated water samples from 5 WWs per year, in order to detect differences in NOM, NOM-fraction concentration and composition prior to (raw water) and after treatment with different technologies. Supply RO isolated and thoroughly characterized NOM reference material.
Preparation of reports and publications.
- WP3 Results preparation, assessments and reporting
- WP4 NOMiNOR-workshops
- WP5 Final report with conclusions and recommendations
- WP6 Project management
A number of municipalities and water treatment works (WTWs) are participating in NOMiNOR:
1. IVAR (N)
2-3. Bergen kommune/Bergen Vann (N; 2 WTWs)
4. NRV (N; river source)
5. Norrvatten (SE; Görvälnverket)
6. Sydvatten (SE)
7-8. VIVAB (SE; Kvarnagården and Kärreberg WTWs)
9-10. Scottish Water (2 WTWs, OBF and NF)
The involved research Institutes/ Universities include:
SINTEF, University of Oslo (UiO), Norwegian University of Life Sciences (UMB), and Cranfield University (UCRAN).