BIRMINGHAM — In Water Technology’s Contaminant of the Month featured in the April issue, Technical Editor Dr. Joseph Cotruvo writes about mercury. Cotruvo discusses what it is, where/when mercury occurs, the potential health effects, analyses, available water treatment and how mercury is regulated in drinking water.

Mercury, a silvery metal, forms a wide range of organic and inorganic compounds, including Hg+1 and Hg+2 salts, sulfides and oxides, as well as organometallic compounds such as dimethylmercury and methylmercuric chloride, and complexes with amines, explains Cotruvo.

Cotruvo continues that mercury and its compounds have many industrial and commercial uses, and the salts have been used as biocides.

Both mercury and its compounds are mobile, reports Cotruvo, and they enter the environment through the combustion of fossil fuels and biological process producing alkyl mercury compounds, which are much more toxic than the salts and elemental mercury.

The use of mercury has been decreasing due to toxicity and environmental concerns, states Cotruvo.

Food is the principal source of exposure, primarily from fish and fish products, and when it comes to drinking water, it is only a minor source of exposure, informs Cotruvo, adding, “Mercury was found in only 42 of 989 groundwaters used for drinking water in the 1988 National Inorganics Reconnaissance Survey; 26 were detected below 0.2 µg/l, and one exceeded 2 µg/l.”

According to Cotruvo, when ingested/inhaled, mercury can accumulate in the kidneys and cause toxicity, and inhaled mercury is neurotoxic.

In the article, Cotruvo lists the following water treatment options for mercury:

  • Conventional coagulation, sedimentation and filtration can remove about 80 percent of inorganic mercury and about 30 percent of organic mercury.
  • Powdered activated carbon (PAC) and granular activated carbon (GAC) are effective for both forms, so POU and POE devices can be applied.
  • Cation exchange is also a possible treatment.

The U.S. Environmental Protection Agency’s (EPA) MCL for inorganic mercury is µg/l (0.002 mg/l), notes Cotruvo, which is the same for the one- and 10-day Heath Advisories, and the World Health Organization (WHO) drinking water guideline is 6 µg/l.

You can find April’s Contaminant of the Month on mercury here.