Caring Works

The Lowell (Mass.) Regional Wastewater Utility reduces energy usage more than 30 percent with the right attitude and a host of plant upgrades

Being green is about many things for the City of Lowell (Mass.) Regional Wastewater Utility (LRWWU), but it’s mostly about caring. “People who work at treatment plants must be aware of our impact on the environment,” says executive director Mark Young. “It’s everything we do in our jobs.”

It’s an attitude that works for this 32 mgd activated sludge plant, which began focusing intently on energy and environmental initiatives in 1996, when Young took his current position. Since then, energy consumption at this ISO 14001-certified operation dropped from 10 million MWh in 1996 to less than 6.7 million MWh — all the while processing 6 mgd more water than 13 years ago.

Years of effort save ratepayers some $400,000 per year. Additionally, the utility recently scored 90 out of 100 on a U.S. EPA ENERGY STAR program that evaluates treatment plant efficiency in energy use and wastewater flow. That compares with an average score of 55 nationwide.

“In the days when energy was cheap, people didn’t feel it was important,” says Young. “That’s a bad philosophy. From a cost and environmental standpoint, you should care whether energy is cheap or not.”

Employee ideas

Lowell’s approach begins with employee-generated ideas, a concept that coincides with the ISO 14001 environmental management program. “The reality is that when you get to large capital improvements, you’re going to see reductions in energy use,” says Young. “But it’s very important to first involve employees in anything that affects the environment, and to get everyone thinking along the same lines.”

Employee involvement led to a host of improvements, such as the use of fluorescent energy-efficient lights and motion sensors that save about $20,000 each year. Another employee idea was to rotate pumps on and off during dry weather to deliver water from six clarifiers to the grit removal system. By not running all pumps continuously, the plant saves as much as $12,000 per year.

Saving with upgrades

While operational measures have always been key, Lowell also looks to equipment upgrades to improve efficiency and save energy.

“We’re fortunate to have the backing of the city manager and city council in moving forward with upgrade projects,” says Young.

Projects completed since the late-1990s include:

Aeration system improvements. Mechanical surface aerators were replaced with a Sanitaire rubber membrane fine-bubble diffused air system. The upgrade also included Roots energy-efficient blowers and a new SCADA system for better control.

Pump upgrades. Older influent, return activated sludge (RAS) and waste activated sludge (WAS) pumps were replaced with Fairbanks-Morse high-efficiency pumps and U.S. Electrical motors (Emerson Motor Company) with variable-frequency drives.

Heating conversion. Natural gas replaced electric heaters to heat 12 pumping stations that feed the plant. The local gas utility helped fund the conversion. Lowell also converted from electricity to gas to heat domestic water throughout the treatment plant.

Replacing motors. Old motors that were sent out for rewinding were replaced with GE high-efficiency motors.

Whether it’s a major upgrade on an aeration system or regular motor replacement, Young says it all adds up. “It’s not just one or two things,” he says. “And it’s not just big projects. It’s the little projects and the big projects that come together to produce results.”

A higher level

With the help of a consultant, the utility identified other initiatives to reduce energy usage and the plant’s environmental footprint. Projects range from automatic setback controls that reduce heating levels on a more consistent basis, to electric sub-meters that provide real-time energy use data.

New technologies also are in store. One initiative is to replace centrifugal blowers on the aeration system with high-speed turbo blowers that promise to increase efficiency and minimize maintenance. Another plan is to use roof-mounted solar panels to generate electricity on site and to install wall-mounted solar-heating systems to heat process buildings in winter.

The plant also will install green roofs on five major buildings. A green roof includes a waterproofing and root-repellent system, drainage system, filter cloth, lightweight growing medium, and plants. The roofs are expected to save on heating and cooling costs and reduce stormwater runoff.

The green roof is Young’s idea. “People in my position are more than just department heads,” he says. “Among other things, we are financial officers, energy managers, physiologists, and environmentalists.”


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