AWWA WQTC60697

The main objectives of this research were to examine the effects of colloidal and particulatematter in fresh waters on dissolved organic carbon (DOC) and UV₂₅₄ determinations, and to develop some guidelines for filteringfreshwater samples having widely varying turbidities. Over ninety percent of the organic matter in thenatural waters tested in this study was in the dissolved form and filter cake formation did not have asignificant impact on the DOC values of a sample. The experimental results showed that the level andcharacteristics of turbidity in a water sample, as well as the nature of pore structures and pore sizedistributions of a membrane filter selected for filtration play important roles in UV₂₅₄ and SUVA₂₅₄determinations. Measuring turbidity in the filtrate of a sample is a simple way to validate the UV₂₅₄, andthus SUVA₂₅₄, results. The results indicated that when filtrate turbidities were below 0.3 NTU, nosignificant impact of filtration volume, filter cake formation, and separation (or pretreatment) processesoccurred on DOC and UV₂₅₄ determinations, and thus calculated SUVA₂₅₄ values. However, when filtrateturbidities were higher than 0.5 NTU, UV₂₅₄ results were affected by residual turbidity values, which alsoadversely impacted calculated SUVA₂₅₄ values. These findings suggest that a conservative criterion forthe turbidity of a filtered UV₂₅₄ sample, such as less than 0.3 NTU, can be adopted to minimizeinterferences on the results. Selection of small pore size filters (e.g., 0.2- or 0.1-µm) and pretreatment ofsamples (e.g., prefiltration, settling) may be used to alleviate the problems caused by colloidal materials ina sample. It was also found that a minimum of 25-mL filter-to-waste volume (i.e., for hydrophilicpolyethersulfone filters or hydrophilic polypropylene filters of 47-mm disc size) would be applicable forvarious natural water samples with varying degree of turbidities prior to collecting samples for DOC andUV₂₅₄ determinations. Includes 11 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/15/2004

Number of Pages:

21

File Size:

1 file , 2.7 MB