Spatial and temporal evolution of trihalomethanes in three water distribution systems

• Published in: Water research (Oxford) 2001-04, Vol.35 (6), p.1572-1586
• Main Authors: Rodriguez, Manuel J, Sérodes, Jean-B
• Format: Article
• Language: English
• Subjects: Applied sciences; Canada, Quebec; chlorination; distribution systems; Drinking water and swimming-pool water. Desalination; drinking water regulations; Exact sciences and technology; Halogens - chemistry; Methane - chemistry; Pollution; regression models; Seasons; trihalomethanes; Water Supply - analysis; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(00)00403-6

Spatial and seasonal changes in trihalomethane (THM) concentrations were investigated in three distribution systems of Quebec (Canada) which are supplied by different surface waters and which use a variety of physicochemical treatment strategies. The investigation was based on an intensive 25-week sampling programme, undertaken at a time of year when the temperature of southern Quebec surface waters exceeds 4°C (April–November). THMs and other water quality and operational parameters were monitored at points along the distribution system — between the treatment plant and the system extremities — which represented variable residence times of water. Results showed that THM concentrations vary significantly (from 1.5 to 2 times, depending on the utility) between finished waters as they leave the plant and water at the system extremities. When water temperature exceeds 15°C, spatial THM variations are particularly high (from 2 to 4 times, depending on the utility). The development of multivariate regression models showed that water temperature was a better predictor of THM seasonal variability than chlorine dose, surrogates of natural organic matter and pH. Also, initial THM formation (in finished waters leaving the plant) was a good predictor of THM levels at distribution system extremities.