Abstract
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 ?g/L in the synthetic matrix compared to 309 ? 15 ?g/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.
Highlights
Koji je generisan elektrohemijski iz kiseonika, primenom generatora ozona Argentox, kapaciteta 1 g/h, uvođen je u vodu kroz difuzer smešten na dnu kolone pri protoku gasa od 8 L/h
Dve litre vode je nakon filtracije (0,45 μm filter) i zakišeljavanja na pH 2, propušteno kroz kolonu sa ispunom od 60 ml DAX-8 smole
U vodi prirodnog matriksa nakon oksidacije preovlađuju hidrofilne strukture (65%), dok je u slučaju sintetičkog matriksa utvrđena jednaka distribucija hidrofobne i hidrofilne frakcije (≈50%)
Summary
Stanovništvo Srbije u regionima Bačke i Banata za vodosnadevanje koristi pretežno podzemnu vodu. Jedan od osnovnih problema u ovom regionu i najčešći uzrok neprihvatljivog kvaliteta vode za piće jeste visok sadržaj prirodnih organskih materija (POM) [1], koje nastaju kao rezultat interakcija između hidrološkog ciklusa, biosfere i geosfere. Imajući u vidu sve strožije zahteve u pogledu kvaliteta vode za piće, neophodno je sadržaj prirodnih organskih materija, kao prekursorskog materijala dezinfekcionih nusprodukata, minimizirati tokom tretmana vode za piće. Utvrđeno je da je formiranje halosirćetnih kiselina u vodi za piće u direktnoj korelaciji sa sadržajem organskog ugljenika, koncentracijom bromida i pH vrednosti tokom hlorisanja. Porast koncentracije bromida postepeno pomera formiranje hlorovanih HAA (monohlorsirćetna kiselina, dihlorsirćetna kiselina i trihlorsirćetna kiselina) prema bromhlor halosirćetnim kiselinama [13], što takođe zavisi od pH vrednosti vode, temperature i relativne distribucije hidrofobne i hidrofilne frakcije POM [14]. Na taj način omogućeno je da se ispita uticaj strukture i porekla organskih materija, odnosno uticaj različitih matriksa na podložnost oksidaciji ozonom
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