1. Joint Utility Board Sewage Treatment Plant: History, Treatment Process, and Performance Overview
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Presentation for:
Saanich Peninsula Inlet Protection Society
By:
Clay Reitsma, M.Eng., P.Eng.
Senior Manager, Engineering
District of North Cowichan
March 14, 2019

3. Presentation Outline Treatment Process Description
Performance of Treatment Facility
Q&A
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4. Treatment Process & Flow Path
Cell 1
Cell 5B
Cell 2
Cell 5A
Cell 6
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Cell 4
Cell 3

5. Treatment Unit Processes
The treatment system has many different components that work together to treat the wastewater. They include:
Screening Removes larger inorganic material (plastics, rocks).
Degritting Removes heavier/finer inorganic material (sand).
Oxidation Converts organics to micro-organisms for subsequent removal by sedimentation.
Settling Settles out micro-organisms.
Alum Addition Removes phosphorus.
Chlorination Kills bacteria and viruses in the process water.
De-Chlorination Removes residual chlorine byproducts from the effluent prior to discharge to the river.
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6. Treatment Unit Processes
Cell 2
Cell 1
Cell 3
Cell 4
Cell 5A
Cell 5B
Cell 6
Screening & Degritting
Oxidation
Oxidation / Settling
Settling
Alum Addition
Disinfection
De-Chlorination
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7. Treatment Unit Processes: Screening
Removes larger inorganic material (plastics, rocks).
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Fine perforated plate screen screens out larger inorganic material.
Screened wastewater passes through to the degritting process.
Captured solids (screenings) are washed, pressed/dewatered, and conveyed into a covered holding container.
A fan draws odourous air from the system and scrubs it through a biofilter.

8. Treatment Unit Processes: Degritting
Removes heavier/finer inorganic material (sand).
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Total of four grit channels.
Flow velocity is maintained at 1 ft/sec to allow heavier/finer inorganics to settle.
Grit is removed from the channels monthly and deposited into Cell 6.

9. Treatment Unit Processes: Biological Oxidation (Cell 1)
Converts organics to micro-organisms.
Cell 2
Cell 1
Cell 3
Cell 4
Cell 5A/5B
Cell 1
Cell 2
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Wastewater flows from the grit channels to Cell 1.
Purpose is to convert organic matter (which exerts an oxygen demand in receiving waters) to micro-organisms (which will settle in subsequent ponds).
By settling out the micro-organisms in subsequent cells, the organic matter is removed from the liquid.

10. Treatment Unit Processes: Biological Oxidation (Cell 1)
Converts organics to micro-organisms.
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Air is provided to mix the water and bring micro-organisms in contact with their food (organic matter).
Air is also provided as a source of oxygen. The micro-organisms need oxygen to survive.
Air diffusers hang from flexible laterals that float on the surface of Cell 1.
Flexible laterals are designed to move from side to side to maximize mixing. This significantly reduces aeration costs.

11. Treatment Unit Processes: Biological Oxidation (Cell 1)
Converts organics to micro-organisms.
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Air is provided by two 150 kW blowers .
One blower is a standby unit. There is provisions for a third blower in the future when additional aeration diffusers are added (can add 50% more diffusers).
The blowers take air from the atmosphere, pressurize it and send it to the diffusers that are submerged in Cell 1.

12. Treatment Unit Processes: Biological Oxidation (Cell 1)
Converts organics to micro-organisms.
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The diffusers have tiny holes that release small bubbles.
The bubbles mix the water.
The bubbles also dissolve into the water and provide oxygen for the micro-organisms.
This is a fine bubble system. More efficient for transferring oxygen to water.

13. Treatment Unit Processes: Settling (Cells 2 & 3)
Settles out micro-organisms that were grown in Cell 1.
Cell 2
Cell 1
Cell 3
Cell 4
Cell 5A/5B
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Process water from Cell 1 flows to Cells 2 and 3.
After organics are converted to micro-organisms, the organics must be extracted from the process water to reduce CBOD5 and TSS in the effluent.
Since the micro-organisms are heavier than water they settle out.
Every 10 to 15 years the settled material is removed and deposited in Cell 6.

14. Treatment Unit Processes: Alum Addition
Removes phosphorus.
Cell 1
Cell 5A/5B
Cell 2
Alum Storage & Pumps
Cell 3
Cell 4
Flash Mix / Floc Channel
Alum Storage
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Process water flows from Cell 3 to the flash mixing/flocculation channel.
Phosphorus is a nutrient that is removed using a chemical called liquid alum. Phosphorus exists in dissolved and particulate forms.
Alum reacts with dissolved phosphorus to form a heavy sticky particle (floc).
The flocs stick to other solids (including particulate phosphorus) and settle out.

15. Treatment Unit Processes: Alum Addition
Removes phosphorus.
Flash Mix / Floc Channel
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Alum Pumps
Alum is pumped to the flash mixing/flocculation channel.
The alum is rapidly mixed with the process water using flash mixers.
The process water is gently mixed in the flocculation channel to form floc particles.
After exiting the flocculation channel, the floc particles begin to settle.

16. Treatment Unit Processes: Chlorination
Sterilizes the process water.
Cell 2
Cell 1
Cell 3
Cell 4
Cell 5A
Cell 5B
Cell 6
Disinfection
De-Chlorination
Sodium Hypochlorite Metering Pumps
Sodium Hypochlorite Storage Tanks and Containment Area
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Chlorine solution (sodium hypochlorite) is injected in the channel between Cells 4 and 5A.
The chlorine concentration is monitored at the outlet of Cell 5A to ensure the concentration is high enough to disinfect the effluent.

17. Treatment Unit Processes: Dechlorination
Removes excess chlorine from the effluent.
Cell 2
Cell 1
Cell 3
Cell 4
Cell 5A
Cell 5B
Cell 6
Disinfection
De-Chlorination
Sodium Metabisulphite Storage Tanks & Metering Pumps
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Sodium metabisulphite solution is injected at the outlet of Cell 5B.
The chlorine concentration is monitored at the outlet of Cell 5A to ensure there is no chlorine left in the effluent.

18. Effluent Quality: Summary
Compliance testing is based on point by point data except in the case of Fecal Coliforms tested against the swimming standard limit of 200 CFU/100 mL which is based on the median of 7 samples.

19. River Water Quality: Summary

20. Environmental Impact of Lagoons
Effluent Quality
VERY GOOD (meets limits in 99% of samples; 3017 out of 3052 samples).
River Water Quality
No significant difference in WQ upstream to downstream of outfall (compliance w WQGs is 94.9% upstream, 95.7% downstream).
Typically when downstream results DO NOT meet BC WQG limits it is because upstream results DO NOT meet the BC WQG limits.
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21. Glossary
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22. Thank You Q&A