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Turbidity, Chlorine Levels & the New Seymour Filtration Plant

Metro Vancouver announced last month (January 2010) that the newly completed Seymour Filtration Plant is now fully operational and delivering filtered water to most of Vancouver and Richmond. The purpose of the new facility is to reduce the presence of turbidity (fine sediment), control disinfectant in our water and corrosion in the infrastructure of our water supply.

Turbidity

Turbidity – cloudy water – is not a contaminant per se; however it can mask the presence of disease-causing micro-organisms. By filtering the water, the presence of these organisms can be controlled thus reducing the amount of chlorine needed to disinfect our tap water.

Turbidity is created when fine particles like sediment or organic matter wind up in the reservoirs through heavy rainfall. Other causes of turbidity can be construction, system operational changes, high water flows due to a fire or flusher truck filling, or high flows due to hot weather.

Turbidity is measured in units called nephelometric turbidity units (NTUs). Daily turbdity readings are posted on Metro Vancouver’s site for all 3 reservoirs supplying Metro Vancouver – Capliano, Seymour and Coquitlam.

Coquitlam Reservoir Treated Separately

Current readings (mid-February 2010) indicate that Capilano is closed (due to excessive turbidity) and that Seymour’s turbidity levels are dramatically reduced (due to the new filtration plant) compared to the Coquitlam reservoir – which is not part of the new Semour/Capilano filtration project. Water from the Coquitlam reservoir will remain unfiltered but is treated with ozone and ultra-violet light before being chlorinated.

Seymour/Capilano Fitration Plant – Phase 2

The launch of the Seymour Filtration Plant represents the debut of the first phase of the larger Seymour/Capilano Filtration Plant which is now scheduled for completion in 2013. The Seymour and Capilano Reservoirs will be joined by 7km twin tunnels that are currently being bored through the North Shore mountains!!

The objective is to filter water from both reservoirs at one plant and shunt the water back to its original mountain reservoir for gravity fed distribution to municipal locations. The yet unfiltered Capilano reservoir is currently not in use due to excessive turbidity.

The new Seymour plant is presently supplying both Seymour and Capilano destinations. This water is currently averaging around pH 7.4.

Boosting Chlorine Levels

Chlorine is introduced into the water as a disinfectant before leaving all three locations – Capilano, Seymour and Coquitlam treatment facilities. This is called ‘primary treatment’.

As water flows through the distribution system, the chlorine introduced during the primary treatment stage gradually breaks down. ‘Secondary treatment’ sites introduce more chlorine to prevent bacterial regrowth as water travels to homes, businesses, and industries. Ozone cannot be used as a secondary disinfectant because it breaks down too quickly. UV treatment also is not an option, since it leaves no residual disinfectant in the water.