Montpelier’s Wastewater Resource Recovery Facility (formerly Waste Water Treatment Plant) treats approximately 1.8 million gallons of sewage daily and is the highest consumer of electricity of all municipal services. But through the dedicated efforts of city employees at the facility, the amount of energy it takes to treat each gallon of wastewater has decreased by nearly 75% between 2007 and 2015. The combination of improvements to mechanical motors and processing systems, in combination with a doubling of the volume of waste processed, has saved the City money on energy expenditures and also reduced greenhouse gas emissions by installing a methane flare. In addition, the facility uses methane captured from processing to heat the primary digester year round and one building in the winter months, saving over 25,000 gallons of oil a year. The photovoltaic panels on the roof also produced over 52,000 kWh of electricity in 2014.
The City of Montpelier received a 2015 Governor’s Award for Environmental Excellence in recognition of the Wastewater Resource Recovery Facility’s (WWRF) implementation of energy conservation measures that save approximately $58,000 a year in utility electricity costs, which translates to about 475 megawatt hours of electricity a year. The WRRF also received the 2015 Wastewater Utility Award from the NEWEA Utility Management Committee for operations and performance excellence and energy conservation.
With a current staff of only four employees, the 3.97 MGD facility, led by Chief Operator Christopher Cox, collaborated with Efficiency Vermont to review plant systems and then implemented various efficiency and operational improvements. In 2015, the team pursued additional opportunities to increase efficiency and reduce methane emissions, including:
- Capacitor Project: In August of 2015, the Independent Capacitor Corporation approached the Operators with the idea of installing a 600V capacitor. The average power factor for the facility is 86.3%. Green Mountain Power (GMP) requires a 95% power factor. Each month the facility is financially penalized for not meeting the required power factor. Installing the correct size capacitor should increase the facility’s power factor to 95% or above. GMP has projected the savings to be $3,740 annually if the power factor of the facility reaches 95%. The cost of a 600V capacitor plus installation, which was guaranteed to increase the facility power factor to 95%, was quoted at $5,600. The project was completed in late October, 2015.
- Methane Improvements: In September of 2015, a new methane flare was put online for the facility’s three digesters. With better control over the ignition pressure set point, Operators are able to stop harmful methane gas from reaching the atmosphere. A flow meter was also installed to record the total amount of flared methane gas each month. With this information, we will be able to better understand the feasibility of any future projects using methane as an energy source beyond the current use for heat at the facility.
- Power Usage Monitoring: In August of 2015, with funding from Efficiency Vermont (EVT), power monitoring equipment was installed. The equipment monitors and records the electrical demand from all the main circuit breakers in the facility. Operators can now see real time electrical demand for all the major equipment. The total project cost was $12,344. EVT contributed $4,000 towards its completion. The purpose of installing power monitoring equipment is to lower the facility’s peak demand charges from GMP. In 2014 the facility’s average monthly peak load was 246kW. EVT estimated a potential savings of $3,800 per year if the facility could lower its average monthly peak load to 225kW. Power monitoring equipment will allow the Operators to understand when peak loading is occurring at the facility and what equipment is causing the demand. This real time information will allow the Operators to efficiently coordinate equipment usage, which should help lower the facilities peak loads. Currently, baseline electrical demand for all the major equipment is being established. The next step will be to prioritize equipment needs during peak loading events. The final step will be to establish average monthly peak loading goals. Each year, with continued energy efficiency improvements, the Operators hope to continually lower the peak loading.
- Sewage Grinder Elimination: In June of 2015 a sewage grinder, which uses a three horsepower motor, was eliminated from daily use. The sewage grinder was installed before the facility had any influent screening. After influent screening was installed the grinder really had no use, but because the grinder was in line with the primary sludge pipes it had to be turned on each day so it would not impede flow of the primary sludge to the pumps. The inline grinder was removed, eliminating a three horsepower motor from running roughly three hours each day.
For more information on Montpelier's efforts to transform its energy system visit: https://netzeromontpelier.org/2016/01/19/clean-water-less-electricity/