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Sniffing Out Mercury

Article provided by the Minnesota Technical Assistance Program

Burr Technology Inc., of Little Canada, received a notice of violation from MCES after submitting its required water test results in January. Specializing in mechanically polishing and removing burrs from metal parts, Burr Tech exceeded the legal wastewater limit of two parts per billion of mercury. Burr Tech was given 30 days to reduce wastewater mercury levels before MCES would order the facility not to discharge to the sewer.

“I hadn’t realized we were in violation. I was totally surprised by it,” said owner Remi DuCharme. “I thought perhaps it was from a job we were running at the time we were tested.” No mercury was found after looking at material safety data sheets and testing deburring chemicals used on the days yielding high mercury levels. Not knowing where else to look, DuCharme contacted the Minnesota Technical Assistance Program (MnTAP) for help.

Karl Dewahl, MnTAP engineer, suggested Burr Tech look at chemicals containing sodium hydroxide, which can be contaminated with mercury. But none of the chemicals tested were a source. Dewahl’s mercury research pointed to mineral abrasives, thermoset plastic liners—made of polyurethane—and plastic polishing media as possible contaminant sources. Consulting Ed Swain, Minnesota Pollution Control Agency (MPCA) mercury expert, confirmed his theory. To zero in on the mercury source, Burr Tech had MPCA use its Lumex, a mercury vapor analyzer, to scan the facility.

The Lumex detected mercury vapors coming from two of Burr Tech’s 11 tumblers. Burr Tech tested the polyurethane liners of the two tumblers and found that the samples contained 24 parts per million of mercury. Burr stopped using the problem tumblers and passed the next three-day wastewater test ordered by MCES. Because the vendor had switched to a mercury-free liner since DuCharme bought the liners two years before, he was able to get the vendor to replace the tumbler linings at cost.

“I knew turning up water flow when samples were taken was not the right way to solve the problem. It is not fair to the environment or to the industry,” said DuCharme. Turning up water flow may increase a company’s problems. Consistent differences between test results submitted by a company and MCES can lead to increased sampling frequency and enforcement actions.

For more information about preventing mercury contamination, or to request a site visit from a MnTAP engineer or scientist to get customized suggestions for your operation, call 612/624-1300 or 800/247-0015