Montpelier's wastewater treatment facility. Photo by John Lazenby.
As of Jan. 2, leachate is once again being trucked to Montpelier’s wastewater facility from Casella’s landfill in Coventry, the only lined landfill in the state. At the same time, ammonia levels in the plant’s wastewater discharge are a concern as the facility will likely fail to meet anticipated new permitting limits.
The Montpelier Water Resource Recovery Facility had stopped accepting landfill leachate in early May, after high E. coli levels were detected in water leaving the plant. Workers later determined that the leachate was having a detrimental effect on the facility’s UV disinfection system, according to Kurt Motyka, Montpelier’s public works director. Leachate is the fluid that builds up as rainwater and other fluids trickle through trash and accumulate.
Motyka hopes to learn soon whether Casella will be able to meet a July 1, 2023 deadline that the city council set for pre-treatment of leachate for per- and polyfluoroalkyl substances (PFAS) at the landfill, before the leachate can be trucked to the Montpelier wastewater facility. Also known as “forever chemicals,” PFAS exist in especially high concentrations in landfill leachate, cannot be removed by the Montpelier facility’s current capabilities, and are tied to a number of health problems in humans.
Motyka noted that several steps were or will be taken to address the issues that had caused the city to stop accepting leachate: the plant is only taking two loads of leachate daily, and the leachate tank was thoroughly cleaned. The tanks will be cleaned more frequently going forward, he said, and workers will also test for E. coli levels more frequently. Motyka said these changes were developed in collaboration with the state’s Wastewater Management Division.
Another issue on the horizon is ammonia levels in water the plant treats. Currently, said Motyka, the facility operates on a “monitor-only permit” for ammonia, but he noted that the state of Vermont has stated that the plant is to have an ammonia limit in its forthcoming permit, which Motyka expects to receive within the next couple of months. Enforcement will not be immediate, but changes are needed to meet the anticipated permitted ammonia levels, he said.
As a result of current permit conditions, the facility has data on ammonia levels in its discharge, Motyka said, and “we expect that we’ll have to make some changes at the plant in order to meet the new permit … so we are including an evaluation within our final design contract for the Phase II project.” Motyka explained that a new process to address ammonia levels will likely entail an additional aeration tank and other steps to bring down the levels of ammonia being discharged.
Leachate may play a role here, as well. “Leachate is relatively high in ammonia,” Motyka said. “We did a study with (engineering consultants) Brown and Caldwell to look at what level of impact is related specifically to leachate, and there is an impact,” reinforcing the need for the new system to address ammonia. But additional treatment procedures for ammonia would likely have been necessary, leachate or no leachate, Motyka said. “Basically the conclusion of the report is that we would likely need to make some changes at the plant regardless of whether or not we took leachate, but there is an impact on ammonia at the plant from leachate.”
