The objective of this study was to examine the spatial and seasonal evolution of THMs in two
large size utilities based on a high-frequency data collection program. The two utilities are located
in the Quebec City region (Canada). Because the collection of data related to chlorination byproducts (CBPs) in water utilities
in the province of Quebec was not mandatory before June 2001, there is currently very little
information concerning variations in these compounds between the plant and the distribution
system. The paper lists the general characteristics of the utilities under study.
The data for this analysis were generated in two different phases. Phase 1 represents a study of trihalomethanes
(THM) variations carried out between May 1999 and September 2000, and Phase 2 represents a
simultaneous study of both THMs and haloacetic acids (HAAs) carried out between September 2000 and September
2001. Phase 1 was designed to compare THM levels, on a seasonal basis, between the entrance
point of the distribution system (following post-chlorination) and the system extremities. Phase 2
was designed as a study of the spatial evolution of THMs and HAAs based on sampling at several
locations within the distribution system. The criteria for selecting sampling points within the
distribution systems were numerous: the points had to be located at variable distances from the plant,
to favor variable residence times of water; they had to be located on-line from upstream to
downstream; at least one point had to represent the extremity of the distribution system; all
points had to be supplied directly by the treatment plant, so there was no influence of rechlorination
facilities or water storage within the distribution system; and, all points had to be
accessible for sampling the same day, every week over a year.
For both Phase 1 and Phase 2 from May to September (a period at which the variations of surface
water temperature are greater) samples were collected weekly or twice per month in order to
assess the variations on water quality in detail. From October 1999 to April 2000, the period when soil
and surface water are covered by snow and ice, variations in water temperature are far less notable
and samples were collected monthly. The collected samples were analyzed for different water
quality and operational parameters: pH (pH-meter); temperature (portable thermometer); free
residual chlorine (DPD titrimetric method, Standard method 4500-Cl); total organic carbon- TOC
(total carbon analyzer using unfiltered samples); UV-254 absorbance (UV/visible
spectrophotometry); and, THMs and HAA5 (E-capture chromatography, EPA 551,2 and 552,2 methods,
respectively). The first three parameters were measured in the field, the others in the laboratory at
Universit¿ Laval. The procedures used for the conservation of the samples between their collection
and analysis were those recommended by Standard Methods (APHA, AWWA, WEF, 1996). Includes 13 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 360 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 10 |
| Published : | 06/16/2002 |
