Duteau Creek Water Treatment Plant

Facing the fallout of an unsuccessful borrowing referendum to add a $30 million filtration facility to the existing Duteau Creek Water Treatment Plant (DCWTP), the Regional District of North Okanagan (RDNO) needed a creative solution to reduce the public health risk within their water system.

WSP rose to the challenge, leveraging their expertise in UV disinfection and relevant Okanagan project experience to design a customized approach. Through technical and project delivery excellence, WSP met the owner’s challenge, delivering a $7 million solution to their $30 million problem — ahead of schedule and under budget.

The Duteau Creek Water Treatment Plant (DCWTP) treats up to 162 million litres of water each day, and is one of only two sources that supply the agricultural, commercial and industrial industries and the some 62,000 residents who call the Greater Vernon region home.

The DCWTP’s existing dissolved air flotation clarification (DAF) and chlorine disinfection processes did not meet the provincial treatment objectives for a surface water source. In addition, the DCWTP had historically been challenged to consistently achieve the disinfection by-product (DBP) limits set out by Health Canada.

The DCWTP was originally designed to add filtration in the future, which would meet the outstanding treatment objectives. Lacking the necessary funds for this upgrade, the Regional District of North Okanagan (RDNO) investigated creative alternatives.

The RDNO began conducting in-situ validation of the DAF treatment performance to establish the spectrum of risk across the treatment process. The outcome lead to UV disinfection being identified as a viable alternative to filtration. This risk assessment allowed the RDNO to secure $7 million in grant funding from the Canadian Water and Wastewater Fund (CWWF) for the innovative application of UV disinfection. Four key issues remained:

1. Tight Design and Construction Schedule: CWWF required the eligible funds be spent on or before March 31, 2018. This required procurement of major equipment and breaking ground in less than six months (a process that typically takes a year).
2. Unconventional Treatment Approach: Obtaining consent from health regulators demanded an advanced knowledge of UV treatment technology and effective collaboration.
3. Reliability: With the UV system proposed downstream of the Treated Water Reservoir, every drop of water passing through the process goes directly into the distribution system. Rapid changes in flow or water quality could result in inadequate treatment and a risk to public health. Historical power surges and ‘brown-outs’ further threatened infrastructure resiliency.
4. Site Footprint, Topography and Hydraulics: There was limited developable area within the already established site, making constructability extremely challenging.

• Provide a UV disinfection process that meets the Ministry of Health 4-3-2-1-0 treatment objectives, namely 3-log (99.9 per cent) inactivation and dual (2) barrier protection, without filtration.
• Design and tender the UV disinfection facility within a six-month timeframe to meet the government grant funding deadline.
• Provide a UV disinfection process that is robust, reliable and capable of meeting the treatment targets through a wide range of operating conditions.
• Deliver an operator-orientated design for equipment layout, maintenance, and function.
• Optimize chlorine dosage to improve water quality through improved chlorine dose control to reduce potential DBP formation.

WSP successfully implemented an accelerated project delivery approach to complete the design and tendering, including obtaining all permits and approvals, for the unconventional treatment approach within a six-month period. Advanced procurement of the UV disinfection equipment established the physical and operational constraints, allowing the design to proceed with confidence and certainty.

Treatment process resiliency through an innovative power supply solution that utilized an inline 350kW UPS, and a broader water quality operating range. Together these ensured the process would continue through power interruptions, and meet or exceed treatment targets for more than 99.9% of the known operating conditions.

Installed in July 2018, the 650 kVA capacitor bank has increased the power factor from below 0.80 to greater than 0.96, saving the RDNO over $750 per month in utility penalty charges and energy use premiums.

Finally, the project was delivered under the $7 million capital budget, indefinitely deferring the $30 million capital expenditure for filtration.