City of Sultan
Challenge
Established in the late 1880’s, the City of Sultan has a rich heritage as a logging, mining and agricultural community. To accommodate a growing population, City administrators knew infrastructure upgrades at its Wastewater Treatment Plant were needed. In addition, its Booster Pump Station, which serves potable water to City residents and fire system, as well as backwash to the potable water treatment facility, was not able to maintain system pressure during peak flow events, its electrical generator was undersized, and the building itself was at the end of its useful life. The City initiated two projects, the first to upgrade its Wastewater Treatment Plant, followed by upgrades to resolve the issues at its Booster Pump Station.
Key objectives: Wastewater Treatment Plant
The City’s key objectives for its Wastewater Treatment Plant
were to avoid capital costs that would be required to maintain its
aging infrastructure, to reduce energy costs by using more efficient
equipment and improving processes, and to maximize operational
efficiencies. The City also wished to upgrade its controls system for
the benefit of plant operators, and improve exterior lighting quality
and safety.
Key objectives: Booster Pump Station
The City also sought to avoid costs associated with maintaining
the antiquated equipment at its Booster Pump Station. For the
continued health and safety of its residents, the City wanted a
redundant potable water system that would ensure the facility
maintained code requirements and reduced the risk of system failure.
In addition, the City wished to increase capacity to help meet peak
demand, reduce energy costs and extend the life of its systems.
Solution
Project I: Wastewater Treatment Plant
After working with Trane to complete a city-wide Preliminary
Audit, the City selected the company to implement an Investment Grade
Audit (IGA) of its Wastewater Treatment Plant through the State of
Washington Energy Savings Performance Contracting (ESPC) program
administered by the Department of Enterprise Services. During the IGA,
Trane identified opportunities to improve the treatment process and
increase energy efficiency. Relying on the Trane Building Advantage™
portfolio of energy services, Trane presented a solution that
maximized grant and utility incentive dollars, improved system
operation and addressed capital improvement needs. IGA data was used
to prioritize proposed energy conservation measures (ECMs) and used to
project energy savings to assist in obtaining grant dollars from the
Department of Commerce and energy conservation incentives from
Snohomish PUD to enable the project.
Maximizing energy and process efficiency
A dissolved oxygen (DO) sensor was installed in the oxidation
ditch and integrated into the plant’s SCADA system to provide
operators with accurate DO levels. Programmable logic controller (PLC)
programming was completed to automatically control mixer and aerator
speed to maintain a constant DO level in accordance with demands of
the biological process. By allowing operators to set two anoxic
cycles per day instead of one, the programming changes will enhance
present and future operations. It maximizes energy and process
efficiency, while providing aeration to meet required levels and
mixing in oxidation ditches. The heat pump was replaced with a new
pump correctly sized for present and future operations. Twenty-three
yard lights and wall packs were replaced with LED fixtures, and five
fluorescent fixtures were retrofit with T-8 lamps and electronic
ballasts to improve exterior lighting quality and safety, while
maximizing energy efficiency.
Project II: Booster Pump Station
Trane began with an Investment Grade Audit (IGA) to identify
and prioritize ECMs for implementation. The project consisted of
process and efficiency improvements to increase peak capacity and
system reliability, replace aging equipment and generate
energy/operational savings. Five booster pumps were installed to
replace end of life equipment, and an abovegrade metal building was
constructed to improve the potable
water system infrastructure
and increase capacity to meet current peak demand conditions. To
further increase capacity and provide redundancy, an emergency
generator was added adjacent to the building. The improvements help
maximize energy efficiency while meeting water demands of two zones,
and supplement flows required during a fire event. The SCADA system
was expanded to improve flow monitoring and alarming, and aesthetic
improvements were implemented.
Results
City of Sultan Wastewater Treatment Plant and Booster Pump Station
upgrades are helping to ensure the continued health and safety of area
residents and accommodate the needs of a growing population. Results
include:
Wastewater Treatment Plant
- Utility cost savings of more than $7,700/yr, with annual
reduction in energy use of more than 92,000 kWh. - Snohomish
PUD incentives estimated at more than $16,000
and Department of Commerce grants of nearly $196,600. - Capital replacement cost avoidance of more than $84,000.
Booster Pump Station
- Utility cost savings of more than $2,700/yr, with
stipulated
energy use reduction of 30,786 kWh/yr. - Snohomish PUD utility incentives estimated at $6,800.
- Maintenance and operational cost reductions estimated at
$12,500/yr for three years.
