Water Treatment Process

Raw lake water enters the pumping station located on the south shore of Buffalo Pound Lake, through two submerged intakes. 

The raw water then flows through “fish screens” which filter out large debris, such as sticks, logs, fish etc., which could damage the pumps. Once through the “fish screens”, the raw water is pumped to the treatment plant via two pipelines connecting the pumping station to the main treatment plant.

After reaching the Plant, water is initially divided into two streams, each of which moves through the cascade de-gasification, coagulation/flocculation and clarification stages. The streams are then recombined for the final stages of treatment, including filtration, carbon adsorption, UV disinfection, and chlorination.

The Cascade process for de-gasification is normally used in times when there is excessive dissolved oxygen levels in the raw lake water. Excessive levels of dissolved oxygen in the water is the by-product of significant algae growth, and ice-cover in the winter or calm light winds in the summer.

The dissolved oxygen must be removed using the cascade system. During cascade de-gasification process, the water falls over a series of steps. This process releases the excess dissolved oxygen and prevents the formation of oxygen bubbles in later treatment processes.

Oxygen bubbles can attach to particles in the water that have formed a fluffy precipitate called floc, causing these particles to float rather than sink. These floating particles can bind to the filters, reducing their capacity to remove floc.

If taste and odour in the water becomes elevated during winter months, and the granular activated carbon (GAC) system, (Stage 6), is not in use, PAC is added to the Flocculation stage to aid in reducing taste and odour.

In this stage, aluminium sulphate (alum) is vigorously mixed with the water. During the process, the alum neutralizes surface charges on any natural organic matter contained in the water, and forms a fluffy material (floc), causing the material to precipitate, or drop to the bottom of the tank. The floc also entraps particulate matter such as sand, silt algae and clay.

In the fourth stage, the floc-bearing water flows through settling basins called clarifiers, where most (more than 95%) of the floc with its entrapped impurities is allowed to settle to the bottom, while clear water is removed from the top.

The clear water is then chlorinated for disinfection. The settled floc is removed from the clarifiers as sludge and is pumped to holding lagoons where it is further separated into clear water (returned to the lake) and solid sludge (removed for disposal).

In the fifth stage, any floc still remaining in the clearwater, following the clarification process, is removed by filtration. The filters used, are a mixed-mixed media, and consist of anthracite, silica sand, garnet sand, and gravel.

The remaining floc is removed as the water passes through these mixed media layers. Periodically, the accumulated floc trapped in the filter layers must be removed by a cleaning process called backwashing.

The process involving Stages 1-5 to this point, is called Conventional Treatment, and is very effective at removing almost all particulate impurities. Some dissolved organic impurities that cause taste and odour however are not removed by Conventional Treatment. During the warmer months of the year, another treatment process called Carbon Adsorption (Stage 6) is added, to remove any taste and odour in the water.

The Carbon Absorption phase is included only during the warmer months of May to December. It involves large rectangular tanks (contactors) which contain Granular Activated Carbon (GAC) to a depth of 3 metres.

Water is lifted by Archimedes screw pumps from the bottom of the mixed media filters to the top of the contactors, where it is allowed to flow down through the Granular Activated Carbon. The Granular Activated Carbon contains many microscopic pores which adsorb dissolved organic impurities.

The water takes about 15 to 30 minutes to move through the Granular Activated Carbon, depending on flow rates. Passing through the Granular Activated Carbon frees water of the dissolved organic materials which cause objectionable taste and odour.

The Granular Activated Carbon filtration process is used to address cyanobateria growth in water, which is largely the cause of the water’s poor taste and odour.

Following the Filtration stage (or in the warmer months following the Carbon Absorption stage), the water is then disinfected using Ultraviolet light. UV light is germicidal to microorganisms.

Very good water quality is important for UV efficiency (high transmittance) thus reactors are installed after conventional treatment.
While UV Disinfection is especially effective for inactivating microscopic parasites such as Giardia and Cryptosporidium it doesn’t alter the water quality, as do other disinfectant products.

UV Disinfection however is not an ongoing disinfectant, so chlorine must also be added after UV disinfection.

Chlorine is added to the water in the final stage, following the UV Disinfection. As a disinfectant, chlorine is very effective at inactivating bacteria and viruses, and is the most commonly used drinking water disinfectant.

In fact, chlorination has been used to improve the safety of drinking water in Canada for the past 100 years. The process helps to ensure water is free of microorganisms that can cause serious and life-threatening diseases.

Once cleaned and disinfected, high quality clear water is pumped from the Buffalo Pound Water Treatment Plant to the cities of Regina and Moose Jaw, and a number of other agencies which supply water to the Regina and Moose Jaw region.

The Buffalo Pound Water Treatment Plant supplies drinking water to approximately 260,000 residents from across southeastern Saskatchewan, on a daily basis.