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GE’s Monsal 70 System creates “Class A” Biosolids for land disposal. Photo credit: GE

GE announced the city of Rexburg, Idaho, has selected the company’s Monsal advanced anaerobic digestion and Monsal 70 technologies to treat biosolids (sewage waste) at the city’s wastewater treatment facility. The project represents the first North American application of GE’s Monsal technologies that will allow Rexburg and other municipalities to meet federal standards for disposing treated biosolids, the company said.

GE’s Monsal technology uses an advanced anaerobic digestion process to treat biosolids, and GE’s Monsal 70 system pasteurizes the sludge, creating “Class A” biosolids for disposal. Anaerobic digestion is a biological process in which microorganisms break down biodegradable material in the absence of oxygen. Methane-rich biogas produced by the system can then be used to produce electricity and heat.

The U.S. Environmental Protection Agency (EPA) governs biosolids under the Part 503 rule. Biosolids that have gone through an accredited process, defined in 40 CFR Part 503 for pathogen reduction, are deemed to be “Class A.” The Monsal 70 system is a patented pasteurization process that is recognized by the EPA as an acceptable treatment process to produce “Class A” biosolids—or biosolids with reduced pathogens. With this classification, no land application restrictions exist, which provides plant owners long-term certainty of biosolids disposition. GE says the Monsal 70 system is an economical alternative to other processes since it does not require any specialized operating permits or staffing.

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Located 28 miles northeast of Idaho Falls, the city of Rexburg selected GE’s technology because it needed a new solution to treat sludge from the wastewater treatment plant prior to landfill disposal in order to ensure it complied with the EPA’s sludge disposal standards.

“GE was the only company that offered the specialized equipment that we needed to install before the winter months begin so that we can meet our federal environmental requirements,” said John Millar, public works director, Rexburg. “This technology will help us upgrade our wastewater treatment plant to meet the needs of our growing population.”

The biogas generated from the anaerobic digestion process will be used to fuel the pasteurization boilers. A heat recovery system is being installed to capture and convert the biogas to heat. GE will provide all of the Monsal anaerobic digestion technology, and a separate contractor will supply the building and installation of the piping and ancillary systems. Aqua Engineering, the design engineer on the project, worked closely with the city of Rexburg and GE to fit GE’s technology into the existing footprint of the city’s wastewater treatment plant.

GE is scheduled to deliver its equipment by fall 2015, and the digestion system is expected to begin operating in late 2015.

In July 2014, GE announced it had agreed to acquire Monsal, a private U.K.-based water, waste, advanced anaerobic digestion and integrated biogas-to-energy business.