Page 4: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Formaldehyde
Analytical Methods and Treatment Technology
Formaldehyde in drinking water is generally analysed by high-performance liquid chromatography following derivatization with 2,4-dinitrophenylhydrazine and liquid-solid extraction. The detection limit is 6.2 µg/L.Footnote 17Using liquid chromatography, formaldehyde recovery was shown to exceed 90% for concentrations ranging from 20 to 200 µg/L. Footnote 4
Huck et al.Footnote 11 studied the formation and removal of formaldehyde at various treatment steps in an Edmonton drinking water pilot plant that was testing ozone. There was little removal of formaldehyde as a result of coagulation-flocculation-sedimentation treatment steps, although peak concentrations were reduced occasionally to an appreciable extent. As noted above, the mean concentration increased in raw water from 1.2 µg/L to 2.2 and 3.2 µg/L following ozonation at 0.5 and 1.0 mg ozone/mg non-volatile organic carbon, respectively. A significant reduction in formaldehyde formation was observed as the water temperature decreased. The subsequent dual-media filtration step decreased formaldehyde levels to between 0.5 and 0.9 µg/L for three of four filters tested. The mean effluent formaldehyde levels following granular activated carbon (GAC) contactors were in the range of 0.3-0.6 µg/L.Footnote 11 Formaldehyde was reduced to non-detectable levels when passed through a GAC column with a solution of ozonated humic material.Footnote 9
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