Polymer Dosing to Increase Sewer Capacity

Project Highlights

Kerr Wood Leidal was retained by the Resort Municipality of Whistler (RMOW) to help solve a potential flow capacity problem with its main sanitary sewer that serves the municipality.

During the 2010 winter games, a record number of visitors were expected at Whistler.  If it rained in Whistler during the games, KWL’s sewer modelling indicated that there was a possibility that high sanitary flows combined with excessive inflow and infiltration flows could exceed the capacity of the main trunk sewer.  This could result in sewer overflows.

As an effective and cost-effective alternative to installing a larger trunk sewer or other capacity management options, KWL explored the feasibility of adding polymer chemicals to the sewer flow to reduce water friction in the pipes and increase the capacity of the existing sewer.  KWL designed and managed a full-scale pilot demonstration system and conducted a performance study.  The results showed that the capacity of the sewer could successfully be increased by adding small doses of a polymer chemical.

The polymer system was activated during the 2010 games and placed in stand-by mode in case there was a rain-on-snow event.  KWL oversaw the operation and maintenance of the polymer dosing system throughout the games, including system trouble shooting and process control.

While it was fortunate that there was no rain-on-snow event during the games, and the extra capacity was not needed, RMOW’s engineering department rested easier knowing that their system could handle such an event.  This approach is useful for other situations when there are short-term capacity problems in gravity or force-main sewer systems.