The City of Woonsocket recently took the first step towards notifying all pertinent parties that it will be phasing out the acceptance of liquid sludges at the municipality’s sewage sludge incinerator (SSI). The City Council unanimously approved a resolution to that effect at its May 22nd meeting.

An unsigned copy of the City Council Resolution obtained by NEBRAMail, dated March 4th, sets forth the reasons for the action in a number of “whereas” clauses. Those include factors such as liquid tank trucks taxing the City’s transportation and wastewater infrastructure and, especially, odors. The resolution also blames the SSI operator for the permit violations at the City’s WRRF.

The Woonsocket SSI is co-located on the property with the City’s water resource recovery facility (WRRF) on Cumberland Hill Road in Woonsocket, on the banks of the Blackstone River. The City contracts for both WRRF and SSI operations with Jacobs Engineering and Synagro, respectively. All three entities are the subject of legal action by the Rhode Island Attorney General’s office taken in March 2023 (see 2023.03.15-Complaint-State-v-City-of-Woonsocket-et-al-1.pdf (rhodeislandcurrent.com)) after a spate of discharge permit violations.

The Resolution is considered the initial notice to all impacted communities. The City Council pledges a “fair leadup time to allow other communities reasonable notice to find alternative options to dispose of their merchant liquid sludge” and commits to a “formal and viable plan including timeline” for the phase out of acceptance of liquid sludges.

The Woonsocket WRRF supplies about 10% of the sludge volume coming into the SSI. The rest is considered available for merchant sludge, mostly trucked in by Synagro under contract with numerous municipalities in the region. The Woonsocket SSI can process about 105 dry tons of sludge per day, with about half of that – about 50 dry tons per day – currently in the form of liquid, non-dewatered sludge. Synagro has completed notifying all its customers about the City’s plan to phase out liquid sludge, however, there is no phaseout timeline or plans available yet.

For perspective, 50 dry tons of sludge per day is equivalent to the amount of sludge processed by the Upper Blackstone Clean Water (UBCW) SSIs in nearby Massachusetts so this action will have a significant impact. Communities impacted include the third largest city in the state, Warwick, as well as South Kingstown, Narragansett, and several others that send their liquid sludges to the Woonsocket SSI. Connecticut and Massachusetts facilities will be impacted too, especially smaller ones that still generate liquid sludge. Dewatering will become even more critical now for these facilities.  

The Rhode Island Department of Environmental Management (RIDEM) and the regional office of the U.S. Environmental Protection Agency (EPA) are aware of the situation but were seemingly surprised about the Resolution. Although these regulatory agencies have major concerns, they are not responsible and have no role in developing capacity for biosolids management. They can only enforce permits when there are solids violations. However, RIDEM, like a few other state environmental agencies in the Northeast, is working on long-range plans for managing biosolids from the state’s 19 WRRFs.

Some NEBRA members cannot wait for the EPA or their States to figure out what to do with biosolids. The Narragansett Bay Commission (NBC), for example, operates two of the largest WRRFs in Rhode Island and needs to make some decisions about its ageing solids infrastructure and contracted services. NBC has partnered with UBCW and Springfield Sewer & Water to investigate the feasibility of a regional biosolids treatment facility to service the three utilities, plus some capacity left over for the region. In addition, NBC has sketched out the Rhode Island Intrastate Wastewater Solids Regional Management Project, a proposed central facility for receiving, dewatering, and drying Rhode Island wastewater solids.

The Woonsocket SSI was originally constructed in the 1970s using multiple hearth furnace technology. Synagro took over operations in 1988. In 2007, the SSI was upgraded and replaced with fluidized bed technology. There were also major upgrades in 2016 to comply with 40 CFR Part 62, Subpart LLL (mercury capture system). The SSI is slated for additional $30 Million in capital improvements that will facilitate the acceptance of only dewatered sludges or “cake”.

It is unclear what, if any, operational impacts can be expected with the switch to cake only.

It is also not clear what the next steps will be on the City Council’s part or whether additional actions will be required to implement the liquid sludge phaseout.