The characterisation ofr dissolved organic carbon and its influence on tri-halomethane formation potential

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  • David Hughes

    Research areas

  • PhD, School of Biological Sciences

Abstract

Dissolved organic matter is best described as a mixture of soluble organic molecular structures derived principally from the degradation of plant matter by natural processes that occur in mineral and organic soils. The water industry currently utilise water catchments that are predominantly lowland or upland wetlands. These generally consist of bogs and fens that are currently under threat from changes in the global weather systems which pose a threat to the natural carbon cycling of these eco-systems.
Dissolved organic carbon (DOC) when disinfected during water processing reacts to form a series of disinfectant by products (DBPs) which have been reported to be detrimental to human health. With the threatened destabilisation of the water industry’s water catchments, this thesis examines the character of the DOC being received into four lakes/reservoirs and attempts to establish what aspects or DOC characteristic relates to its reactivity when it is chlorinated with HOCl.
The series of samples were collected on a 30 day cycle for 24 months with every third month’s samples being fractioned using DAX 8 and XAD 4 resins and an in-house designed and built instrument. The samples were characterised using a number of established literature methods and the tri-halomethane potential (THMFP) was determined by Gas Chromatography/Electron Capture Detection and Solid Phase Micro Extraction. Analysis of the samples highlighted differences in the DOC concentrations of the lakes over the seasons and the influences of dry, wet and cold periods upon the characteristics and concentration of the DOC. The results identified the lowland Cefni lake as the most responsive to environmental influences, but it had the lowest THMFP. The highest was
exhibited by the upland Conwy lake DOC which also demonstrated the least response to external environmental influences. The dry/wet event investigated illustrated the differences between mineral and peat catchments, demonstrating rapid increases and decreases in DOC concentrations in the Mineral streams with relatively slower responses in the Peat stream. Although the upland Peat DOC peak concentration was higher than that of the upland Mineral, it was the upland Mineral that demonstrated the highest THMFP/mg of DOC.
Overall the results have indicated that the THMFP is independent of DOC concentration and that there is no single inference that controls their formation, but is a combination of a number of factors with ring substitution being the foremost influence.

Details

Original languageEnglish
Awarding Institution
Supervisors/Advisors
Thesis sponsors
  • Natural Environmental Research Council (NERC)
  • Dwr Cymru Cyf (Welsh Water)
Award date2013