AWWA WQTC52754

Choral hydrate (CH) and aliphatic aldehydes are generally found at higher levelsin drinking water that has been disinfected with ozone. In laboratory studies, CHwas formed from the chlorination of acetaldehyde (ACD) at pH > 7 but not frommethyl glyoxal. Controlled laboratory studies on the chlorination of acetaldehydeunder conditions of pH (6.7, 7.6, 8.8) and temperatures (4 degrees C and ca 21degrees C) typical of Canadian drinking water supplies revealed that the level ofCH increased initially with contact time (0 to 10 days). However, at higher pH(8.8) and temperature (21 degrees C), CH reached maximum levels within 2 days andsubsequently decreased with a concurrent increase in the level of chloroform, but50% of the available ACD was consumed after 10 days contact time and only 63% ofthe molar concentration of ACD consumed appeared as CH or chloroform. In a surveyof 6 drinking water facilities, CH was observed in water samples at pH < 7 whichindicates that the chlorination of ACD is not the only precursor of CH inCanadian drinking water supplies and the increased levels of CH in ozonated watercannot be explained solely from the chlorination of ACD. In the survey, a suite ofaldehydes (including ACD) and CDBPs (including TCM and CH) were found in thetreated and distributed water from all three treatment processes. The levels ofCH exceeded the World Health Organization provisional guideline of 10 ug/L in 7of 60 individual samples, in 1 of 12 seasonal averages, and 0 of 6 yearlyaverages. Includes 11 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

01/01/2000

Number of Pages:

13

File Size:

1 file , 290 KB