Meeting Stringent Mercury and Heavy Metal Discharge Limits
By E.H. Kelle Zeiher, Ph.D., Al Foster, and Maurice Smith, Ph.D.
The Federal limit for mercury (Hg) emissions from industrial and municipal sites is set at < 12 parts per trillion (ppt) Hg. Practically speaking, this is equivalent to the amount of Hg in rainwater. The federal limit is a maximum, with various states and regions in the United States proposing even stricter limitations. For example, the Great Lakes Regional Collaboration (GLRC) imposes limits of 1.3 ppt Hg in their emission guidelines. Likewise, sites that empty into the Ohio River (policed by the Ohio River Valley Water Sanitation Commission [ORSANCO]) may adopt mercury limits lower than the federal limit. While the regulatory climate is largely propelled by the North American (U.S.) restrictions, other global regions are likely to follow the lead of the U.S. Environmental Protection Agency (EPA) in demanding lower Hg emission limits. Mercury is not the only regulated species. Other pollutants of concern include, but are not limited to arsenic (As), cadmium (Cd), chromium (Cr), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se), vanadium (V), and zinc (Zn). Strict fines can be imposed on industries that exceed the discharge limits on their individual permits (1). For industries, a process shutdown can result in a ﾓsuperfundﾔ site that requires remediation and continued expense for the foreseeable future. Indeed, many industries budget millions of dollars for long-term remediation.
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