Innovative Retrofit Saves Energy, Tax Dollars

An energy-efficient upgrade project at the Bergen County Utility Authority (BCUA) wastewater treatment plant in Northern New Jersey will save electricity, reduce pollution, and produce over $14 million in measured savings for taxpayers.

The project involved switching from electric motors to natural gas engines to drive the plants aeration blowers. The engines burn methane gas produced by the wastewater treatment process, rather than purchased natural gas. Heat from the engines is captured and used for processes formerly heated by the facilitys boilers. This triple punch at energy expense saves BCUA almost $1 million annually and creatively "disposes" of the plants methane gas.

To initiate the upgrade project, BCUA engaged Onsite Sycom Energy Corp., an energy services company (ESCO). Based on an existing energy audit, Onsite Sycom and its engineering contractor suggested replacing one base load electric motor with a natural gas engine to drive the aeration blowers, and adding a fifth blower driven by a second gas engine. The estimated savings would be approximately 2,700 kilowatts of electricity and $477,000 in energy costs per year.

Using the plants methane byproduct to fuel the gas engines and using the heat from the engines to heat the buildings doubles the energy dollar savings - from $477,000 to $942,300 per year. The estimated total net energy savings over the 15-year life of the ESCO contract is $14,134,800.

The entire retrofit project was accomplished at no cost to BCUA through participation in a Demand Side Management (DSM) program for ESCOs offered by the local power utility. The utilitys "Standard Offer" payments covered all costs of the retrofit, so BCUA was able to keep 100 percent of the energy cost savings generated by the project.

In addition, BCUA will receive rebates from the electric utility totaling approximately $870,000 over the 15-year life of the contract. The monthly rebates are tied to a comprehensive, long-term measuring and verification program that monitors the consumption of energy delivered. Monitoring and verification is carried out by Measuring & Monitoring Services, Inc. (MMSI), an independent energy monitoring firm in Tinton Falls, New Jersey.

Equally important to BCUA is measuring energy consumption to get the most out of each retrofitted system. The performance of the Caterpillar gas engines and other retrofitted equipment is monitored over the life of the ESCOs performance contract to ensure that it is meeting expectations - and to identify equipment requiring maintenance.

Sensors attached to the BCUA gas engines and backup electric motors feed consumption data to MMSIs TF32A+ energy monitors located throughout the facility. The monitors TimeFrame? software periodically uploads data via phone lines to MMSIs central station where it is processed into energy management information. This information is delivered in reports and online data bases to assist BCUA in effectively managing energy consumption and confirming the amount of its utility rebates.

The BCUA facility, encompassing 120 acres containing seven buildings, is the third largest wastewater plant in New Jersey. It processes 60 to 109 mgd and serves 46 municipalities. Prior to the retrofit, a substantial amount of the plants energy was used to operate four 2,250 horsepower aeration blowers driven by two electric motors, with two additional motors for backup.

To meet anticipated demand for wastewater treatment in the rapidly growing suburban county, BCUA began looking to expand its power supply to accommodate an increase in wastewater.

Initially, a cogeneration plant requiring an investment of approximately $8 million appeared to offer the needed increase in power supply. In the process of investigating this option, BCUA learned of the availability of energy efficiency retrofits which would allow for expanded capacity without requiring more power by reducing the amount of energy needed to support the plants operation. BCUA was intrigued by retrofitting as a means of making capital improvements to its facility while reducing energy costs.

After a comprehensive energy audit, two additional opportunities to reduce energy expense were identified. Methane gas is the principal byproduct of the wastewater treatment process, and a source of pollution from the facility. Onsite Sycom proposed using the plants methane to power the new natural gas engines. Fuel use was further reduced, in a cogeneration-like application, by directing the heat from the methane driven engines to heat the processes that were receiving heat from the facilitys boilers. These processes include heating the buildings and elements of the wastewater treatment process.

With this revised design, the facility has substantially reduced, and in the summer months virtually eliminated, the need to purchase fuel to drive the aeration blowers and boilers. The switch to gas engines also was made so that natural gas can be used as a secondary fuel source when the methane waste gas supply does not meet the plants full fuel demand. And, the electric motors that were replaced by the gas engines remain as backup when one of the gas engines is down for service.

"This project is exciting from both a financial and an engineering perspective," according to James Celestino, MMSIs vice president of operations. "It is one of the first energy efficiency projects to employ a direct drive - as opposed to cogeneration - application based on waste gas driven engines. This is as close as we can come with current technology to a perpetual motion machine."

And the project has significant environmental bonuses. The new process of capturing and cleaning the methane waste gas removes and neutralizes its sulfur content before it is burned to drive the gas engines.

The process has sufficiently reduced NOX and sulfur emissions to qualify for emission reduction credits from the New Jersey Department of Environmental Conservation.

"This project has it all," says MMSIs Celestino. "It innovatively combines energy efficiency, immediate energy cost savings, environmental improvement and huge, long term savings for BCUAs customers."