Addressing raw water quality issues
The Queen Charlotte Islands are an archipelago of between 150 and 200 islands located off the northwest coast of British Columbia – this project helped to address their water treatment needs.
The Village of Queen Charlotte with a population of around 1050 is centrally located at the south end of Graham Island.
The Village was unable to meet potable water demands from existing well productions due to salt water intrusion and elevated manganese. Honna River was developed as a new surface water source, but required treatment to address variability in water quality and flow.
The village commissioned the plant in May 2010. The plant has a capacity of 8 L/s (690m3/day) and a 25 year design life.
The treatment processes include:
- A DAF (dissolved air flotation) system to remove colour and other impurities
- Gravity filtration to remove turbidity and protozoa
- Primary disinfection using UV
- Secondary disinfection using calcium hypochlorite
The use of UV for disinfection is making a positive contribution to the environmental sustainability of the project. It is expected to improve resource efficiency in a cost-effective manner and by reducing chemical use also reduce life-cycle environmental impacts.
The project also included construction of an intake in the Honna River and a pipeline to the Village wastewater system to dispose of the backwash residuals. The new plant has been designed to operate in tandem with an existing well supply and treatment system to provide the 2025 maximum day demand.