The Louisville and Jefferson County Metropolitan Sewer District (MSD), Louisville, Ky., was among 25 organizations honored recently by the Environmental Protection Agency and the U.S. Department of Energy (DOE) for their voluntary leadership in reducing energy use and preventing pollution.
MSD won the award as part of the Energy Star program hosted by EPA’s Atmospheric Pollution Prevention Division. The district joined EPA’s Green Lights program in 1991 and the Energy Star Showcase Building program in 1994.
Over the period between FY91-92 to FY96-97, MSD’s energy conservation efforts have saved a total of 20,590,000 kWh of electricity and 2,145,528 ccf of natural gas. The energy savings reduced costs by $1,132,450 for electricity (at an average rate of $0.055 per kWh) and $1,072,764 for gas (at an average rate of $0.50 per ccf). After adding in time-of-day and demand-charge savings, MSD is saving approximately $500,000 annually, according to district figures.
After joining the Green Lights program, MSD hired the Louisville Resource Conservation Council (LRCC) to audit its facilities for relamping and other conservation opportunities. The projects have conserved energy, saved money, reduced greenhouse gases and other air pollutants and increased employee comfort and productivity, a district spokesman said.
“Some of the first things we did were lighting and energy audits,” said James J. Hunt, Director of Physical Assets for MSD. “That led to substantial savings, and we used those savings to fund new initiatives. Instead of looking at each project separately, we looked at several. If we saved a lot on one, we used the savings on other, marginal projects.”
At the main office, special emphasis has been on lighting, heating and air conditioning systems and Energy Star PCs, printers and copy machines.
At garage and shop facilities, weatherization has been the focus. The conversion from electric-resistance to natural-gas infrared space heating in two facilities saves a total of about $20,000 annually, and the employees are significantly more comfortable. As outdoor lighting is upgraded, high-pressure sodium fixtures are being used, in lieu of mercury-vapor.
Time-of-day rates precipitated the shifting of a weekly energy-intensive pumping operation to off-peak hours, saving more than $16,000 annually. New treatment and conveyance facilities are equipped with premium (high-power-factor) motors.
The 77,000-ft2 building which MSD bought and renovated in 1995 for its new main offices was selected for the EPA’s Energy Star Building Showcase Program. MSD made a written commitment to the EPA to halve the building’s overall energy demand via tune-ups and retrofits. EPA projects the building will use only $1/ft2/yr after full commissioning. Also, water-saving plumbing fixtures cut water use by one-third, despite a one-third increase in employees.
A program of eliminating small, temporary treatment plants and pump stations by extending permanent infrastructure is expected to reduce the normalized rate of energy required to convey and treat wastewater. That savings offsets at least part of the additional energy needed to treat the wastewater from new customers, almost 20,000 of whom were previously served by old septic systems.
“A lot of what we’ve done was just learning what we had,” Hunt said. “For example, we negotiated with the local electric company to get better rates. They offer two or three rate structures depending on the volume and kind of energy you use. If you are plugged into the wrong rates, you pay more than you have to. Just changing to the proper rate structure yielded our biggest savings.”
LRCC also found class-of-service billing errors that reduced MSD’s energy bills by about $120,000 a year. These savings were plowed back into the energy conservation programs.
LRCC monitors the use of electricity and gas at all MSD facilities and annually provides usage summaries and analyses. The council placed more than 40 facilities on an electrical demand rate and seven facilities on a time-of-day electrical rate. These rates force MSD staff to consider the cost of installing oversized equipment and the hours of equipment operation. LRCC has also discovered natural gas leaks via monitoring.
Despite the savings generated by the conservation program, MSD’s electrical energy use usually increases, at least at face value, every year due to factors beyond the district’s control. The district regularly acquires new service areas and new and inherited conveyance and treatment facilities. Also, projects to improve effluent quality, such as the addition of bio-roughing towers at the largest treatment plant, often increase energy consumption.
MSD’s energy management efforts have saved enough energy to compensate for all the energy costs of serving additional customers and improving effluent quality with a 50 percent margin of excess savings. However, heavy rain in recent years have driven up pumping costs.
When the level of the Ohio River exceeds a certain elevation, MSD must pump its discharge over the flood wall and into the river. The average year includes 90 days of “flood pumping,” with every day of pumping costing $1,650.
The intensity of rain events in context with soil saturation determines the amount of run-off generated and therefore the amount of additional wet-weather (sewer inflow and infiltration, stormwater and floodwater) flow that MSD must manage. The Louisville area experienced severe storms in May 1995, March 1996 and March 1997. Since some of that stormwater was pumped, and some of what was pumped was also treated at wastewater treatment plants, those storms cost millions of dollars in additional electricity and gas consumption.
Over the period between FY91-92 to FY96-97, MSD’s energy conservation efforts have saved a total of 20,590,000 kWh of electricity and 2,145,528 ccf of natural gas. The energy savings reduced costs by $1,132,450 for electricity (at an average rate of $0.055 per kWh) and $1,072,764 for gas (at an average rate of $0.50 per ccf).
