Evaluating corrosion control strategies for the Dartmouth drinking water distribution system (Nova Scotia).

摘要

The Halifax Regional Water Commission (HRWC) commissioned a new water treatment plant for Dartmouth in December 1998. However, the potential for the new treatment process to negatively impact the distribution system was of particular interest to the HRWC. Bench, pilot and full-scale testing was initiated to (i) assess the potential for pipe tuberculation to detach, and (ii) to develop a long term corrosion control strategy for the Dartmouth drinking water distribution system. The corrosion control methods were compared using total iron, turbidity, and apparent color concentrations.; The bench-scale experiments were designed to investigate the underlying relationships of the various corrosion control strategies with common water quality parameters.; The pilot-scale system used in the investigation consisted of four sections of 100 year old cast iron pipe sampled from a low flow area of the distribution system.; The full-scale investigation used eight sampling points in the distribution system with retention times from 1.5 to 55 hours. In the initial samples collected for the full-scale campaign the corrosion control treatment for the distribution system was pH adjustment to 8.8 to achieve a LSI near neutrality. In the final samples the corrosion control treatment was polyphosphate addition of 0.75 mg/L and pH adjustment to 7.5 to 8.0.; At the bench-scale the iron concentration experiments showed no significant differences for any of the corrosion control techniques evaluated. The chlorine decay experiments showed that polyphosphate addition does not significantly affect chlorine decay rates.; Lime and polyphosphate provided similar performance during the pilot-scale continuous flow and standing periods. However, lime significantly increased post-filtered turbidity levels, which resulted in excessive deposition of insoluble material during the standing periods. At full-scale the polyphosphate addition appeared to provide better corrosion protection than pH adjustment. Thus, polyphosphate should be strongly considered as a viable corrosion control strategy for the Dartmouth drinking water distribution system. (Abstract shortened by UMI.)