The impact of filtrate turbidity on UV<sub>254</sub> and SUVA<sub>254</sub> determinations: Fid-Bau Portal

The impact of filtrate turbidity on UV₂₅₄ and SUVA₂₅₄ determinations

Karanfil, Tanju / Erdogan, Ilke / Schlautman, Mark

The main objectives of this research were to examine the effects of colloidal and particulate matter in freshwaters on dissolved organic carbon (DOC) and ultraviolet light absorbance at 254 nm (UV₂₅₄) and to develop some guidelines for filtering freshwater samples with widely varying turbidities. More than 90% of the organic matter in the natural waters tested in this study was in the dissolved form, and filter cake formation did not have a significant impact on the DOC values of a sample. The experimental results showed that the level and characteristics of turbidity in a water sample, as well as the nature of pore structures and pore size distributions of a membrane filter selected for filtration, play important roles in UV₂₅₄ and specific ultraviolet absorbance₂₅₄ (SUVA₂₅₄). Results indicated that when filtrate turbidities were below 0.3 ntu, filtration volume, filter cake formation, and pretreatment processes had no significant impact on DOC and UV₂₅₄ determinations and thus on calculated SUVA₂₅₄ values. When filtrate turbidities were >0.5 ntu, however, they increased the UV₂₅₄ values (and also SUVA₂₅₄) without causing an apparent impact on the DOC measurements. These findings suggest that a conservative criterion for the turbidity of a filtered UV₂₅₄ sample, such as <0.3 ntu, should be adopted to minimize interferences on the results.