According to experts gathered by NEBRA for a recent Lunch & Learn webinar, there is hope that sewage sludge incinerators (SSIs) can continue to be a solution for many parts of the region. It is certainly worth continued research and development. So NEBRA brought together several members with specific expertise for the September webinar to hear the basics on SSIs, how they are regulated, operation and maintenance challenges, ash recycling opportunities, and the potential for SSIs to break down per- and polyfluoroalkyl substances (PFAS).

SSIs are the prevalent method of managing biosolids in Connecticut and Rhode Island with significant installations in Massachusetts and New Hampshire. SSIs continue to be a major part of the biosolids “market” in the Northeast. When one goes down for maintenance – planned or unplanned – it impacts water resource recovery facilities (WRRFs) throughout the region. Occasionally, but more frequent of late, WRRFs have violated their total suspended solids (TSS) limits when there was no place for their sludges to go. Being able to “waste” solids is the key to effective operations.

To kick off the webinar, Kelley Begin, P.E. with Woodard & Curran presented an “Incineration 101” lesson in 15 minutes, reviewing the types of sewage sludge incinerators, the regulations pertaining to SSIs, and air pollutions controls. We learned that SSIs are more prevalent in the Eastern and Midwest United States and there are two basic types: Multiple Hearth Furnace Incinerators (MHFs) and Fluidized Bed Incinerators (FBIs). Take aways from Begin’s presentation were that there is a limited number of SSIs and that fleet is aging. SSIs require extensive air pollution control systems and significant testing, continuous monitoring, and reporting requirements (she helps 5 SSIs in New England with compliance). Lastly, she cited major Environmental Justice considerations in permitting and operating these incinerators.

Mike Andrus and Joe Parker with Upper Blackstone Clean Water (UBCW) spoke about their experiences operating 2 MHFs in Millbury, Massachusetts. Both these guys have decades of experience in wastewater. UBCW is located in an industrial setting, not in a neighborhood with environmental justice concerns. However, they do serve the greater Worcester area which includes many of those communities (250,000 served). UBCW’s average daily flow is 30 million gallons per day (MGD). The incinerators process approximately 18,000 dry tons annually. UBCW is lucky in that there is an on-site ash monofil with over 20 years of storage remaining.

Next, Persephone Ma, a soil scientist with Brown & Caldwell who did her graduate research on using SSI ash as a phosphorus fertilizer in corn and soybean, spoke about opportunities for SSI ash. She pointed to local examples of beneficial uses of SSI ash. Specifically, NEBRA member Manchester, New Hampshire, works with NEBRA member Resource Management, Inc. to turn Manchester’s ash into a soil amendment. Other beneficial use options include fertilizer (plant nutrients can be available), concrete manufacturing, and structural fill. The main take away from Persephone’s presentation was that, like every WRRF, every ash is different. Testing is required to know what is contained in a facility’s ash.

The last presentation was by Lloyd Winchell from Brown & Caldwell who has become an expert in the fate of PFAS through thermal treatment systems. He is very involved in a lot of the research and has 6 published papers on the topic.  Lloyd shared the results of the research showing the potential for high-temperature processes to transform, remove and maybe even – and he hesitated to use the word -- destroy PFAS. 1,000 degree Celsius is the number to hit based on the published literature presented.

In addition to temperature, as Lloyd explained, time, turbulence and the unique sludge-as-fuel chemistry are all factors in what happens to the PFAS. More research is required and better analytical methods but there is promise for thermal treatment systems to interrupt the cycling of PFAS in the environment. Be sure to watch for the latest research Lloyd had his hand in: Water Research Foundation’s Project No. 5111 which looks at all inputs and outputs from both an FBF and an MHF. It should be published soon. Sneak peek: they found reportable amounts coming from the stack (but below state air guidelines) and the ash was PFAS “free”. 

In response to UBCW’s slide on its operational challenges including age and condition of its 1970s MHFs, redundancy, and parts availability (not manufactured any more), NEBRA heard from another of its members, Industrial Furnace, countering the parts availability issue. According to Industrial Furnace, new and used parts are available for these old MFHs. There is also a network of 20 operating MHFs on the East Coast to share parts.  Bill Lill of Industrial Furnace told NEBRAMail that he was encouraged by the research presented. “It is worth exploring – and it is quite possible – to cost-effectively upgrade the inactive SSI infrastructure in the Northeast,” he said. Then he rattled off a list of half a dozen WRRFs with abandoned MHFs that could add capacity to the region.

In the Northeast, according to EPA SSI permit data, there are 5 MHFs and 6 FBIs facilities operating in New England.

At the end of the webinar, Janine Burke-Wells of NEBRA asked SSI operators to add nitrous oxide (N2O) testing to their stack testing regimes and supply the data to NEBRA for use in updating the Biosolids Emissions Assessment Model (BEAM). She explained that there is not a lot of data on N2O from SSIs because it is generally not regulated by EPA or included in state air permits. N2O is, however, a potent greenhouse gas (GHG) and a factor in the BEAM calculations for SSIs, landfills, and land application/storage.

Members can access this webinar recording via the members-only page: NEBRA Members — NEBRA (nebiosolids.org). Non-members contact NEBRA (info@nebiosolids.org) for how to access.