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Nifty Shades of Gray: Albany Plant Repurposes Municipal Effluent


Courtesy: CH2M HILL 


If there’s an issue that keeps power plant owners up at night these days, it’s water

From tightened regulations to an ongoing drought, where to get water for cooling and process is a continual concern, if not an outright challenge. That means that plant owners have to get creative. One increasingly popular option is municipal effluent.

The Empire Generating Plant in Rensselaer, N.Y., just outside Albany, is a 535-MW plant with a 635-MW peaking capacity. The natural gas–fired combined cycle facility began operations in September 2010 and employs two GE 7FA combustion turbines, two Alstom three-pressure heat recovery steam generators (HRSGs), and one GE D-11 reheat steam turbine. 

Though it’s situated right on the Hudson River, it uses no river water in its operations. Instead, the plant uses non-disinfected municipal secondary effluent as its only process water supply, allowing the facility to conserve freshwater consumption by as much as 4,800 gallons per minute during the summer high-demand period.

A Murky Path Forward

Getting to this point, however, wasn’t easy.

The brownfield site along the Hudson had, for more than 100 years, been used by German manufacturer BASF for a chemical and pharmaceutical factory. In 1999, battered by Asian competition, BASF decided to shut it down, leaving behind a site saturated with solvents and other chemical waste. 

The Empire plant was originally intended for an entirely different location. Local firm Besicorp had pitched the project for a site in Ulster, about 50 miles south. After local officials gave the plan a sour reception, Besicorp looked elsewhere. In 2000, it announced plans to build the plant on the BASF site, following a $10 million hazardous waste cleanup. Though local government officials mostly supported the project, many residents and environmentalists did not. Concerns mostly centered around the cleanup plan—many contended it did not go far enough—and whether the proposed plant would pollute the local air and water. Besicorp would later sell the project to Empire Generating Co., a subsidiary of private equity group Energy Capital Partners.

The state finally approved the cleanup plan in 2003. In early 2004, as cleanup progressed, there was a brief dispute between the city and county over control of the project, which was resolved after state officials intervened. The New York Public Service Commission approved the $800 million plant in 2005. Empire Generating began construction in March 2008 after the state gave the go-ahead. 

Geotechnical issues also proved to be a challenge, as the site was composed of loose Hudson River sediment. Extensive piling would be necessary before the foundations could be laid. 

Construction was overseen by Englewood, Colo.–based CH2M HILL. Mindful of the community concerns, Empire set out to build one of the cleanest, quietest, most environmentally friendly combined cycle plants in the country.

Recycling Water

Core to this goal was limiting the impact on the local water supplies. 

Rather than drawing water from the Hudson—which would have been simpler and cheaper but would likely have intensified opposition from residents and environmental groups, not to mention potentially running afoul of future Environmental Protection Agency regulations—Empire decided to make use of the non-disinfected secondary effluent from the Albany County Sewer District waste treatment plant just across the river. CH2M HILL built a 28-inch graywater pipeline under the Hudson to the plant.

In addition to requiring CH2M HILL to bore a tunnel under the river, this idea also broke ground when it came to health and environmental standards, because there were no applicable state regulations governing the use of secondary effluent for cooling towers. Looking for guidance, the project managers decide to adopt California’s Title 22 tertiary disinfected water quality requirements as a best practice to control potential pathogen vectors from cooling tower drift. This meant employing a combination of treatment processes, including chloramination, coagulation, upflow sand filtration, hypochlorination, and chlorine contact.

In addition to supplying cooling tower water, the municipal secondary effluent is used as the makeup source for service water and demineralized water supplies. The service water is used for evaporative cooler supplies, demineralized water treatment, and miscellaneous process use. Service water is produced by intercepting the upflow sand-filtered effluent and processing it through ultrafiltration, followed by monochloramine addition. Using monochloramine as a disinfectant minimizes the formation of trihalomethane compounds that cannot be removed by the demineralized water treatment process. The filtered service water is then forwarded to the reverse osmosis and mixed bed ion exchange units to produce demineralized water for the HRSGs. 

A Good Neighbor

Given its proximity to residential areas east of the city, noise abatement was also a concern. A variety of mitigation measures were employed: 

  • The turbine buildings are sound insulated, as are the feedwater pumps. 
  • The HRSGs employ stack silencers.
  • The cooling tower uses silencers and low-noise fans. 
  • Sound barricades shield both the HRSGs and cooling tower. 

The Empire plant began supplying power to the state grid in September 2010 and has since garnered several awards for its innovative approach. Local officials have been enthusiastic about the project. “This is a site we thought would be a deserted industrial lot,” said Rensselaer County Executive Kathy Jimino. “So to see it come back like this is great.”

The Empire plant, said Plant Manager Sean Spain, “was a very complex project that overcame many hurdles. The plant is operating as designed and achieved all performance requirements.”

—Thomas W. Overton is POWER’s gas technology editor. Follow Tom on Twitter @thomas_overton.

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