Hemijska industrija 2012 Volume 66, Issue 2, Pages: 253-261
https://doi.org/10.2298/HEMIND110902080M
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The influence of different matrices on the nature and content of haloacetic acids precursors in ozonized water
Molnar Jelena J. (Faculty of Sciences, Novi Sad)
Agbaba Jasmina R. (Faculty of Sciences, Novi Sad)
Dalmacija Božo D. (Faculty of Sciences, Novi Sad)
Klašnja Mile T. (Faculty of Technology, Novi Sad)
Watson Malcolm A. (Faculty of Sciences, Novi Sad)
Kragulj Marijana M. (Faculty of Sciences, Novi Sad)
This paper investigates the influence of different matrices (groundwater a
realistic natural matrix and commercial humic acid solution a synthetic
matrix) on the nature and content of haloacetic acid (HAA) precursors in
ozonized water (0.4 to 3.0 mg O3/mg DOC; pH 6). Natural organic matter (NOM)
characterization of the natural matrix showed it was largely of hydrophobic
character (65% fulvic and 14% humic acids), with the hydrophilic fractions
HPIA and HPI-NA at 12% and 9%, respectively. At approximately the same
dissolved organic carbon (DOC) content of the investigated matrices (~10 mg
/L), a greater degree of hydrophobicity was seen in the humic acid solution
than in the natural matrix, resulting in a higher content of HAA precursors
(559 ± 21 μg/L in the synthetic matrix compared to 309 ± 15 μg/L in the
natural matrix). By applying different ozone doses (0.4 to 3.0 mg O3/mg DOC),
the DOC content of the studied matrices was reduced by 6-22%, with a maximum
process efficacy being achieved with 3.0 mg O3/mg DOC. Ozonation also lead to
changes in the NOM structure, i.e. complete oxidation of the humic acid
fractions in both investigated matrices. After oxidation, hydrophilic
structures dominate the natural water matrix (65%), whereas the synthetic
matrix has an equal distribution of hydrophobic and hydrophilic fractions
(~50%). Changes in the content and structure of NOM during ozonation resulted
in the reduction of the total HAA precursors content (63-85%, using 3.0 mg
O3/mg DOC). Detailed analysis of the reactivity of the residual HAA precursor
materials shows that ozonation using 3.0 mg O3/mg DOC reduced the reactivity
of the NOM fractions in comparison to the raw water. By contrast, HAA
precursor material present in the commercial HA solution was transformed
after ozonation into other reactive compounds, i.e. precursors which
originated from the fulvic acid and hydrophilic fractions. The results of the
laboratory testing indicate that the application of ozonation can reduce the
content of haloacetic acid precursors to some degree. However, in real
applications of oxidative treatment in the preparation of drinking water, as
well as the efficacy in reducing the total organic matter content, the nature
of the residual NOM must also be taken into account, as it can include toxic
reactive precursors to disinfection byproducts.
Keywords: drinking water treatment, ozonation, natural organic matter, haloacetic acids