| The objective of the present research investigation was to compare the corrosiveness of three chlorine based disinfectants on cast iron pipe through the use of both pilot- and bench-scale testing and to observe their impact on water quality. In particular, the three disinfectants studied were chlorine dioxide, free chlorine, and chloramines. The impacts of chlorite, a byproduct of chlorine dioxide, were also observed.; The pilot-scale testing consisted of five recirculating pipe loops. The test pipe was approximately 100 year old heavily tuberculated four inch cast iron pipe. Each test section was five feet long. Corrosion rates were measured using two-electrode linear polarization probes. As well, the pH, temperature, dissolved oxygen, turbidity, color and total iron of both the influent and effluent were recorded. The experiment was conducted at the J. D. Kline Water Supply Plant, which serves the greater Halifax area. The raw water for the study was post-filtered water that was adjusted to a pH of 8 and had a polyphosphate concentration of 0.8 mg/L added to it for corrosion control. The experimental design studied two different retention times (6 and 12 hour) within the pipe loops and both a high and low disinfectant dose for each of the four disinfectants.; The results of the pilot-scale experiment showed that monochloramine was the most corrosive of the disinfectants. Chlorine dioxide was the least corrosive and was not significantly different than the control loop, which had no disinfectant added to it. Chlorine dioxide also did not impact water quality as much as free chlorine and monochloramine. These results indicate that chlorine dioxide would be a viable alternative to free chlorine or monochloramine. (Abstract shortened by UMI.)... |
