The City of Penticton Water Treatment Plant

The City of Penticton is located at the southern end of the Okanagan Valley close to the US border. It has Okanagan Lake to the north and Skaha Lake to the south. It is well known for its sunny beaches, friendly people, wineries, and as home to the Canadian Ironman Triathlon. The City's population is approx. 32,550 and the water system distribution system has 8,100 service connections. The idea for a water treatment plant was conceived in 1986 after several Giardiasis outbreaks and implemented in 1997.

Overview

The original water system was built in the 1920's and consisted of one source, Penticton Creek. The water system was later updated to include pumping from Okanagan Lake during seasonal water quality changes. It has a main storage dam, Greyback, and separate domestic and irrigation systems. Because of the separate systems, construction of a smaller facility was feasible.

The $20,000,000 project included the cost of the treatment plant, construction of pipelines, upgrading a pressure reducing station and Okanagan Lake pump station.

Plant

Two primary sources, Penticton Creek and Okanagan Lake, feed the plant. This allows for the flexibility to choose which source is the best according to quality, supply capacity, pumping costs, and energy savings. The facility is a multi-barrier system that consists of intake structure, flash/rapid mix, coagulation, flocculation, sedimentation, filtration, and disinfection.

Classification:
Level 4 Water Treatment Plant

Specifications:
Nominal Capacity: 60 ML/day
Hydraulic Capacity: 100 ML/day
Average Daily Flow: 21.4 ML/day
Peak Flow: 52.4 ML/day
Minimum Flow: 10.4 ML/day

Intake: Removal of large objects such as logs, leaves, fish and other large foreign objects, done by screening.

• Penticton Creek is fed to the plant by gravity from a reservoir.
• Okanagan lake water is pumped in a dedicated line directly to plant.

Flash/Rapid Mixing Tanks: The primary purpose of the flash mix process is to rapidly mix and equally distribute the coagulant chemical throughout the raw water.

Specifications
Tanks – 4 (2 per train)
Volume - 12.6 m3/train

• Large propellers do the mechanical mixing. Coagulant mixing is achieved in approximately 20 seconds.
• Raw water is pre-chlorinated (Cl2) here to help aid in coagulation and settling.
• The coagulant, Polyhydroxy Aluminium Chloride, is added and mixed rapidly as the raw water enters the facility. The mixing process must be complete and uniform to achieve the proper results.

Coagulation/Flocculation Tanks: Coagulation is the process of clumping fine particles into larger particles, this increase is size and density will allow for removal by settling, skimming and filtering. Flocculation is the process of gentle mixing; this brings the particles together to increase size.

Specifications
Tanks – 6 (3 per train)
Volume - 670 m3/train

• Flocculation tank is a continuation of the mixing process without the velocity.
• The mechanical flocculators are vertical propellers
• Flocculation basins are baffled to prevent short-circuiting of the water

Sedimentation Tanks (Plate Settlers): Removal of large particles that have densities higher then water by settling thus reducing the loading of filters. This is achieved by decreasing the velocity to almost zero so gravity can settle out impurities.

Specifications
Tanks - 1
Volume - 1355 m3

• The sedimentation basin uses plate settlers. These high rate settlers were developed to increase the efficiency of the sedimentation basin
• As water enters the basin, it travels up the plates, decreasing the velocity and increasing the surface area. Settling is achieved by gravity.
• Sludge is collected at the bottom of the settling tank and is removed and discharged to sanitary sewer. It can also be centrifuged.

Filtration: the removal of particulate impurities and floc by passing the water through a filter bed. The impurities can consist of suspended materials (fine silts/sand and clay), colour and biological (bacteria).

Specifications
Number of Filters 6
Filtration Rate 18 m/hr
Filter Size 4.5 m X 10 m
Filter Depth 1.83 m
Medium Type Anthracite
Backwash Rate 650 L/sec or 300m3
Air Scour Rate 46 m3/min

• Water flows through 6 mono-medium (anthracite) gravity filters, which is one of the first installations of its type in Canada.
• Filter run times vary from 48 to 100 hours depending on water source and quality.
• Run time before backwashing a filter is determined by a combination of particle counts, turbidity, and head loss, and is done by mechanical means. This consists of blowers for air scour and vertical turbine pumps for backwash water

Disinfection: the selective destruction of pathogenic organisms.

Specifications
Clearwell 6681m3
Pre & Post Cl2

• Post chlorination is applied to meet distribution needs. Post chlorination allows for protection of the distribution system and reservoirs.
• Full treatment of the water allows the chlorine dose to be significantly lower than it would be if chlorine disinfection were the only form of treatment.

Lab Data

Operation

The City of Penticton Water Treatment Plant and distribution system are operated and maintained by highly trained and certified operators. The plant contains a modern laboratory where water quality is monitored; which in turn assists the operators to adjust the plant performance to meet or exceed Canadian Drinking Water Standards.

Points of Interest

Staff: Dave Evanchu, WT III & WWT I, Greg Mealing, WT II*/WWT II, Brent Edge, WTII*/WWTIII, Brian Edge WT II*/WWT II, Bruce Stickland, Electrician/WT I, Al Laidman, Water Mechanic, WD I *, and Alistair Wardlaw Assistant Water Quality Supervisor. * Greg, Brent, and Brian have recently written their WT III. *Al recently wrote his WT I.

Distribution System
160 Kilometers of water mains
900+ fire hydrants
5 reservoirs
8100+ service connections

• Treatment plant provides protection against Giardia Lamblia, Cryptosporidium, water borne bacteria, and viruses.
• Facility is primary run with blended water from Penticton Creek and Okanagan Lake.
• Blended water requires no pH adjustment.
• Modern SCADA system can control both water treatment facility and remote water supply system from a single location.
• A diesel generator provides backup power with the ability to run plant at full load capacity.
• All laboratory work is done internally, including microbiological tests of which there are approx. 1000/yr.

Thanks to Kevin McLuskey