LEWISTON — City officials are working on ways to stem a significant cost increase in disposing of sewage sludge after the material recently tested high for a chemical linked to cancer and other ailments.

The Lewiston-Auburn Water Pollution Control Authority, like many treatment facilities undergoing state-mandated testing, had levels of at least one type of per- and polyfluoroalkyl (PFAS) substance high enough to merit additional state testing.

The results prompted a decision by LAWPCA’s board of directors to stop sending sewage sludge to local farms for fertilizer for now, but the unexpected shift has officials concerned about the unbudgeted cost to send all of the sludge directly to a landfill.

PFAS, a family of potentially thousands of synthetic chemicals, are known as “forever” substances because they are extremely persistent in the environment and in human bodies.

Treated sewage sludge, also known as biosolids, has been commonly used on farms as fertilizer or distributed as compost. Treatment plants are required to analyze sludge for a number of contaminants, but there had not been a requirement to test for PFAS, until now.

According to a memo sent to the City Council, which will receive an update Tuesday, sending sludge to a landfill is the most expensive option, and could result in a $500,000 budget increase. That means a $320,000 increase in Lewiston’s share of the cost, based on the current split with Auburn based on the amount of waste produced.

As of June 17, 870 cubic yards of material had been sent to the Juniper Ridge landfill, which is state-owned but managed by Casella Waste Systems. According to the council memo, the landfill tipping fee is $60 per ton and transportation costs are more than three times the budgeted average for land application. LAWPCA produces about 32 yards weighing 27 tons, per day.

City Administrator Ed Barrett said Tuesday that the projected cost is based on a “worst case,” if the city is not able to identify other means of disposing of the sludge.

While LAWPCA officials are working on alternatives, they are complicated and depend on oversight and additional testing from the Maine Department of Environmental Protection.

Mac Richardson, superintendent of LAWPCA, said Tuesday that sending all of the sludge to landfill is the “least favorable option,” and that the agency has applied for a six-month “pilot” license to reopen its prior composting facility on Penley Corner Road in Auburn.

In order to do that, the facility will have to pass the screening standards for PFAS levels in the compost and develop certain mixes in order to create compost with the pathogen-reduction requirements mandated by the state. Richardson said that because the facility uses anaerobic digestion — a process in which microorganisms break down material, resulting in biogas that can be combusted to generate electricity and heat — it’s more difficult to create traditional compost.

He said if LAWPCA receives the permit, it would restart the compost program in mid-July, with compost likely available mid-August. Asked what happens if the compost, when tested, exceeds the screening standard for PFAS, Richardson said they would have “little choice” but to continue sending it to a landfill.

Barrett’s memo to the council states that composting could cost between $40 and $50 per ton, and that sending material to farms for land application is the least expensive option at $17 per ton.

In order for treatment facilities that have tested above PFAS screening levels to continue land applications, the DEP is requiring additional testing at sites where sludge has been spread.

This spring, LAWPCA tested 14 hayfields within its land application program. Of those fields, only two were below screening levels and could accept biosolids. Richardson said LAWPCA is pursuing the additional testing to do applications on a limited number of hayfields this summer and fall.

“Some of the material we have stockpiled already and some of it we’ll be making in the future may go to some of those farm fields,” he said.

The initial test in Lewiston showed that its sludge material exceeded the 5.2 parts per billion screening standard for PFOS (one type of PFAS) at 13.8 parts per billion. The other two types of PFAS tested below the limit of detection.

The tests have been conducted statewide for compost produced by treatment facilities. In these tests, the compost is most often exceeding the standard for PFOA, a variation of PFAS, than what is testing high in sludge.

According to Barrett’s memo, in addition to the new material being produced, there is a “large amount of material already stockpiled” on farms and at the former compost facility. LAWPCA is seeking extensions from the DEP on a number of the sites “to allow the material to remain stockpiled until it can be appropriately land spread, composted, or landfilled.”

“I don’t think we’re prepared to make any decision at this point,” Barrett said, adding that the city will be closely watching what happens at the state level. “There’s some question floating around about how much material the landfill can take.”

Last week, David Burns, director of the DEP’s Bureau of Remediation and Waste Management, said that in light of the extra steps needed for treatment plants to continue land applications, many are “finding alternative outlets for their biosolids,” mainly landfills.

Burns did not return an email requesting comment Tuesday about the increased demand on landfills.