For several decades, lobe and multistage blowers were the tried-and-true blower technologies for wastewater treatment plants. Over the past 15...
Name: Wyndgate Satellite Plant, of the Duckett Creek Sanitary District
Location: St. Charles County, O’Fallon, Mo.
Plant size: The sanitary district operates seven total treatment plants—three of which are or will be MBR facilities—and 36 pump stations, treating up to 8 million gal per day (mgd) of wastewater. The district, located outside of St. Louis, treats water in St. Charles County. The Wyndgate Plant is approximately 8,000 sq ft and has a capacity of 1.2 mgd.
Infrastructure: The Wyndgate Plant is a membrane bioreactor (MBR) treatment plant. Instead of using gravity and a settling tank to separate the clean water from the waste, the wastewater is forced through a membrane that filters out almost all sediment and solids and removes virus and bacteria. An MBR plant discharges water that is said to be approximately 10 times cleaner than water that is treated by a traditional wastewater plant.
Last month, a house in a suburb of St. Louis began treating wastewater using MBR technology. Technically, the house is an MBR water treatment facility, but to anyone who lives in the Wyndgate Community, it’s just another one of their neighbors.
Choosing MBR technology
In October 2004, the Duckett Creek Sanitary District (DCSD) began their selection process for new contractors and new facilities. According to Tom Engle, the DCSD’s executive director, the St. Charles County government had just passed a law making traditional package treatment plants illegal. Therefore, an MBR facility made the most sense. They chose ZENON Membrane Solutions, since acquired by GE Water Process & Technologies, to build the first MBR treatment facility in the state. This facility promised to not only treat water more efficiently, but produce less obstruction and odor in the community as well.
“There was a real need in the community for something non-intrusive, and the model of the house disguised as the treatment facility was an attractive idea,” said Donna Hartman, commercial manager of packaging systems at GE.
The technology is also smaller, taking up significantly less space than a traditional wastewater treatment plant would. City officials liked this because it gave the community more land to build residences or use for other recreational purposes. The plant, located in a cul-de-sac on a quiet street, blends into the other 50-plus houses in the Wyndgate Community by having the same landscaping and architectural features as the other residences.
DCSD’s previous technology produced effluent into Lake St. Louis that was not completely filtered, causing residents there to complain. Buildup was also occurring on a nearby stream. The membrane technology promises to block out anything bigger than 0.1 microns, and is said to be 10 times cleaner than traditional wastewater plants, essentially fixing that problem.
The total project took a little over two years to complete; the kickoff meeting occurred in November 2004 and the plant was built and ready to operate in October of 2006. The community needed 50 homes for the new facility to actually start treating wastewater, which it did at the end of March 2007.
The plant is slated to eventually serve 1,400 homes, with more than 700 homes planned for the Wyndgate Community.
After screening, the wastewater undergoes denitrification in an anoxic chamber and then travels to the bioreactor for nitrification, and finally to a membrane process tank for filtration. Permeate pumps are used to gently pull the wastewater through thousands of membrane fibers. Each fiber is filled with billions of microscopic pores that physically block suspended solids, bacteria and viruses from passing through—guaranteeing water quality and clarity on a consistent basis.
Comparing to traditional plants
The total estimated cost for the Wyndgate Plant, which included architecture and landscaping around the structure, was $4 million. While many would think that MBR facilities are more expensive than traditional wastewater facilities, that assumption may not always be the case.
“The cost difference has come down quite a bit … traditional plants have more wraparound costs, because there’s more land and bigger footprints, so costs have become very competitive,” Hartman said. “MBR facilities can even cost less in total production.”
Yet the DCSD MBR facility did cost three to four times what the district would have paid for a traditional plant.
Yet, Engle says, “the ability to expand the plant as growth occurs tends to lessen the initial financial burden.”
The smaller footprint of MBR plants allowed the builders to be more creative with the layout of the facility—i.e., making it look like a house. Another popular option with municipalities is a facility disguised as a barn-type structure, Hartman said. Another satellite plant in the DCSD will be designed as a barn, while the other planned facility will look like a residence.
“Conventional treatment could not fit into a house,” Hartman said. “The technology allows planners and builders to develop a facility that is a central hub of the community without the smell or looming size.”
She also explained that MBR technology has no limit in terms of flow capacity.
These facilities also give community officials the option of selling recycled water from the MBR facility back to the local community in order to create additional revenue.