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Saco River Water Treatment Facility Power Generation

The first ultrafiltration membrane WTP in New England that does not chlorinate its finished water

The Biddeford & Saco Water Company owns and operates the Saco River Water Treatment Facility located in Biddeford. The company provides service to over 35,000 customers located in five separate communities. Average and peak flows are approximately 5.3 MGD and 8.8 MGD respectively. Normal power to the facility consists of a 2,300 volt main service. There were no backup power provisions because the primary service is located adjacent to an electrical sub-station.

Recognizing the potential of losing primary power, the requirement for providing uninterrupted water service to its customers, and due to increasing electrical energy costs, the company hired Wright-Pierce to evaluate and implement a system which would satisfy these needs.

After a detailed evaluation, Wright-Pierce recommended that the company proceed with the implementation of a 2300V stand-by service generation system. The system included a 600 KW diesel generator unit along with medium voltage paralleling switch gear, all housed in a separate custom enclosure located adjacent to the treatment facility. This alternative provides the water treatment facility the ability to meet peak water demands in the event of an electrical power service interruption. The paralleling switch gear was selected to allow operation of the unit and synchronous electrical load sharing with the electrical utility.

The system implemented provides substantial operational flexibility, the unit is upgradeable to a 4160V service, and it is rated for continuous duty service. The company has the ability to convert to self-generation for peak sharing, if needed or desired in the future. This system also required the least amount of modification to the existing electrical system, and installation of this system minimized disruptions to on-going operations.

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Project Highlights

Background

The Biddeford & Saco Water Company wanted to provide uninterrupted service to its customers. They retained Wright-Pierce to evaluate and select an approach for implementing an optimum backup power system. The following four alternatives were considered and evaluated:

  • stand-by service only
  • peak sharing service only
  • stand-by service combined with peak shaving
  • continuous service (self-generation).

Challenges

The evaluation was complicated due to the fact that the primary service voltage of 2300V was used to power only three of the five primary pumping units. The voltage was subsequently stepped down to 480V to power the remaining two pumping units.

Solutions

The 2300V stand-by power generation system was recommended primarily because it provided the most flexibility and met the primary goals of the water company, all within the capital budget allocated for the project.