Water Pollution Control Plant Savings and Energy Conservation

The Building Automation System succeeded in reducing energy costs (natural gas and electricity) at the WPCP. Reducing the heating and ventilating (H&V) requirements in two of the main buildings when unoccupied could lead to significant savings. A computer-based BAS was installed to manage the H&V for:

• Biological Aerated Filter (BAF) building
• Dissolved Air Floatation (DAF) building

Levels of ventilation and heating

By code, specific minimum levels of ventilation and heating are required during both occupied and unoccupied times. We can operate the BAS using either programmable schedules or occupancy sensors to regulate the H&V systems.

Annual savings

Based on current utility rates and average heating degree days, the estimated total annual savings to-date as a result of this project are:

• $84,000/yr Natural Gas
• $29,000/yr Electricity

$113,000/yr Total

Pumping is a significant cost in operating the WPCP. Unfortunately, two of the original (500 HP) main influent pumps were not appropriately sized to meet current average flow rates, resulting in poor operating efficiency (60-70%) and high electrical costs.

Improved efficiency and reduced energy costs

Newer and smaller pumps, sized to meet current flow conditions, would allow for improved overall pumping efficiency (>80%) and reduce energy costs. We replaced the two original 500HP pumps with the more appropriately sized pumps. The estimated total annual savings achieved is approximately $110,000/yr.

The Biological Aerated Filtration (BAF) process at the WPCP is the highest energy consumer at the facility. To operate effectively, this process requires a great amount of compressed air. The original, 2005 design included eight 50 HP and seven 100 HP duty conventional air blowers.

On review, we determined that replacing the existing pressure blowers with new, higher-efficiency turbo blowers would result in considerable electrical savings. With financial assistance from the Government of Ontario, a project was undertaken to replace the existing 15 blowers with three 350 HP turbo blowers (2 base units + 1 spare).

The results

Early results of this project indicate at least a 35 percent electrical energy reduction, or approximately $250,000 in annual hydro savings. In addition to the energy savings, other project benefits include a much safer working environment due to:

• Noise reduction from 120 dB to below 92 dB;
• Fewer oil spills and related housekeeping issues;
• Reduced maintenance requirements and the potential of pinch points, lifting, and other related injuries; and
• Additional savings in reduced maintenance costs and spare parts inventory.

An upgrade of one of the major WPCP process buildings (Screen and Grit) provided an excellent opportunity to investigate new, higher-efficiency high-bay and perimeter lighting. Twenty-three new 122-166W LED hi-bay light fixtures were installed to replace the aging high-pressure sodium lighting.

Energy savings

The new lighting provides an estimated $2,300/yr in energy savings, in addition to longer bulb life (lower replacement cost) and improved overall lighting. This project was partially funded by the Thunder Bay Hydro rebate program to reduce total connected kilowatts.

The WPCP's 600 kW cogeneration (cogen) unit burns waste methane gas to produce electricity and hot water. The hot water heats buildings and processes when required. We use all generated power on site, reducing the need to purchase power from the hydro utility.

Annual savings

Optimizing the cogen to maximize electricity production can lead to significant cost savings. Recent efforts have increased cogen performance by an average of 19%, resulting in additional projected annual savings of approximately $58,000/yr.