Clean Water Advocacy - Newsroom - AMSA in the News
No. 216
Friday, November 9, 2001 Page A-15
ISSN 1521-9402
News
Water Pollution
Permit Limits for Mercury Seen Increasing For Treatment Facilities, City
Officials Say
NASHVILLE--More publicly owned treatment works are finding discharge limits
on mercury incorporated into their Clean Water Act permits in what officials
said Nov. 9 they expect to be an increasing trend.
Part of the reason for the increase is the methylmercury criterion issued by the
Environmental Protection Agency in January, according to Chris Hornback, manager
of governmental affairs for the Association of Metropolitan Sewerage Agencies.
He spoke at a pretreatment coordinators workshop sponsored by EPA and AMSA.
The first-ever water quality criterion for methylmercury takes the unusual step
of considering concentrations of mercury in fish tissue to derive a residue
criterion for methylmercury of 0.3 milligrams per kilogram of fish tissue (2 DEN
A-1, 1/3/01). Criteria for other pollutants are usually set for the water
itself, not for the fish in the water.
More states are looking at mercury limits as National Pollutant Discharge
Elimination System permits come up for renewal, Hornback said. Another driver
for mercury limits is the federal Great Lakes Initiative, which seeks to reduce
pollution in the lakes with an emphasis on bioaccumulative pollutants such as
mercury.
The permit limits pose a problem for POTWs, Hornback said, because few control
options exist, leaving pollution prevention and best management practices as
some of the only viable means of achieving the limits.
AMSA Report
AMSA issued a report in August 2000 showing that a significant amount of mercury
in waste water comes from domestic sources (163 DEN A-10,8/22/00). Domestic
waste water contains an average of 138 parts per trillion of mercury, the
report, Evaluation of Domestic Sources of Mercury, said.
The Northeast Ohio Regional Sewer District (NEORSD) was one of the earliest
systems to have permit limits for mercury. The permit limited the amount of
mercury that was allowed to pass through the facility to no more than 1.3 ppt.
Keith J. Linn, environmental specialist for the district, said that before the
Great Lakes Initiative, Ohio set the water quality criteria for mercury at 12
ppt. After the adoption of the initiative in 1997, the water quality criterion
dropped to 3.1 ppt, and that assumed a daily average consumption of fish of 15
grams per day, which Linn said is higher than the national average of 6.5 grams.
After this limit was set, the initiative moved forward with a water quality
criterion designed to protect wildlife that consume fish. This criterion was set
at 1.3 ppt, Linn said.
Sampling showed the mercury levels from domestic sources averaged about 85 ppt,
Linn said. The 350 dental offices in the region accounted for another large
portion of the mercury concentration.
Because of the high loading from domestic sources--estimated at about 0.17
pounds per day--the district calculated that the maximum allowable mercury
loading from industry would have to be a negative number, Linn said.
The reason is because to achieve the permit limit of no mercury pass-through of
greater than 1.3 ppt, the maximum allowable headworks loading would have to be
0.15 pounds per day. Subtract from that amount the 0.17 pounds from domestic
sources, and the result is a maximum allowable mercury load for industry of
negative 0.02 pounds, Linn said.
"Obviously, that poses a problem," he said.
Ohio EPA issued guidance stating that BMPs may be used to meet local industrial
pretreatment limits, Scott Broski, supervisor of enforcement for the Northeast
Ohio Regional Sewer District, said. They may be used in cases where flows from
industrial users are insufficient to obtain a good waste water sample, where the
calculated numeric limit is below detection levels, or they can be shown to be
the most economically feasible means of regulation.
Ohio Guidance
The Ohio EPA issued guidance in June 2000 on BMPs for industrial pretreatment
limits. Such practices include substituting materials; reformulating or
redesigning the product; modifying equipment, facilities, technologies, or
processes; recycling scrap amalgam or using amalgam traps; and using
alternatives to amalgam where possible.
The NEORSD proposed that some industrial sources submit BMP plans indicating how
they will minimize their discharges of mercury. These plans include inventories
of mercury sources and their loadings, identification and evaluation of BMPs, an
implementation schedule, and methods for assuring progress.
Hornback said some states are considering legislation that could be troublesome
for dischargers such as POTWs. For example, New York is considering a bill
setting mercury discharge limits at below detection levels. Maine is considering
a bill setting water quality criteria at 0.2 parts per trillion.
EPA approved Method 1631 in June 1999 that uses an atomic fluorescence technique
that can detect mercury at levels of 0.5 parts per trillion. The method is about
200 times more sensitive than other detection methods, the agency said.
AMSA, he said, is working with the electric utility industry to study mercury,
its sources, and how it acts in the water column.
"We also need to figure out the issue of legacy mercury," he said, speaking
about baseline loadings of mercury in water.
Other studies are looking at equipment that removes amalgam in dental offices
before it is introduced into the waste stream.
By Susan Bruninga