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. 2016 Oct 20;6:35027.
doi: 10.1038/srep35027.

Climatic, Geographic and Operational Determinants of Trihalomethanes (THMs) in Drinking Water Systems

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Free PMC article

Climatic, Geographic and Operational Determinants of Trihalomethanes (THMs) in Drinking Water Systems

Maria Valdivia-Garcia et al. Sci Rep. .
Free PMC article

Abstract

Trihalomethanes (THMs) are conditionally carcinogenic compounds formed during chlorine disinfection in water treatment processes around the world. THMs occur especially when source waters are subject to marine influences, high and-or regular precipitation, and elevated levels of organic matter. THMs formation is then rooted in geographic, operational and climatic factors, the relative importance of which can only be derived from large datasets and may change in the future. Ninety three full-scale Scottish water treatment plants (WTPs) were assessed from Jan 2011 to Jan 2013 to identify factors that promote THMs formation. Correlation analysis showed that ambient temperature was the primary THMs formation predictor in potable water (r2 = 0.66, p < 0.05) and water distribution systems (r2 = 0.43, p = 0.04), while dissolved organic carbon (r2 = 0.55, p < 0.001) and chloride (indicating marine influence; r2 = 0.41, p < 0.001) also affected THMs formation. GIS mapping of median THMs levels indicated brominated THMs were most prevalent in coastal areas and on islands. This real-world dataset confirms both geographic and climatic factors are key to THMs formation. If ambient temperatures increase, THMs control will become more challenging, substantiating concerns about the impact of global warming on water quality.

Figures

Figure 1
Figure 1
Spatial distribution of median total THMs on 93 drinking water plants around Scotland on a carbon richness soil layer (Jan. 2011–Jan. 2013) (Obtained using http://www.esri.com/news/arcnews/spring12articles/introducing-arcgis-101.html; version ArcMap 10.1).
Figure 2
Figure 2
Median values for (a) Dibromochloromethane (DBCM), (b) chloride, (c) DOC (raw water) and (d) DOC (distribution networks) at 93 drinking water treatment plants in Scotland (Jan. 2011–Jan. 2013). (Obtained using http://www.esri.com/news/arcnews/spring12articles/introducing-arcgis-101.html; version ArcMap 10.1).
Figure 3
Figure 3
Bar plots with standard errors for: (a) median total THMs in potable and distribution samples with ambient temperature (error bars not shown for better visibility but typical ranges appear in Table 1), (b) median DOC in potable and distribution samples, (c) median DOC in raw water with rainfall levels (Jan. 2011 to Jan. 2013).
Figure 4
Figure 4
Correlation plots between monthly average concentrations (Jan. 2011–Jan. 2013) for (a) THMs and ambient temperature, (b) THMs and rainfall and (c) DOC and rainfall. (d) Correlations between bromide and chloride concentrations (Jan. 2011–Jan. 2013).

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References

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