On August 5, 2015, while many people were enjoying boating and fishing on the scenic Animas River in New Mexico, the river was contaminated with 3 million gallons of yellow mining wastewater (link to USA Today article). It was accidentally released from an abandoned mine in Colorado by an Environmental Protection Agency (EPA) cleaning team, which took full responsibility. The wastewater (link to wastewater community) contained high concentrations of arsenic, lead, cadmium and mercury. You can read about heavy metal toxicity in a previous blog post. There may be other toxic heavy metals (link to metal analysis community) as well.
Heavy metals in wastewater do not degrade and are persistent in our environment for a long time, and they must be measured and controlled. Here are some helpful resources about heavy metal analysis.
Wastewater discharge in the U.S. is strictly regulated under the Clean Water Act (CWA) (link to EPA summary). The law only allows wastewater from municipal and industrial wastewater treatment systems to be discharged into navigable water with permits. Treated wastewater can be directly discharged to surface water (direct discharge) or first go through the Public Owned Treatment Works (POTW), often called wastewater treatment plant, before being discharged to surface water (indirect discharge). The direct discharge permits are regulated under the EPA’s National Pollutant Discharge Elimination System (NPDES). The EPA authorizes the majority of the states in the U.S. to administer the wastewater discharge permits under NPDES. Indirect discharge is regulated under the National Pretreatment Program. For permits under both programs, strict industry effluent guidelines (link to EPA effluent guidelines page) must be followed.
The direct discharge of wastewater from industrial sources relies on industrial wastewater treatment facilities to remove pollutants from produced wastewater. However, since the indirectly discharged wastewater is transported to POTW, it must be pretreated to remove large amounts of industry-specific contaminants before reaching POTW. This is to protect the POTW wastewater treatment facility from possible interference by industry-specific pollutants, or contaminant pass-through, as the common POTW is not designed to remove these contaminants.
Different categories of CWA analytical methods include approved methods as well as other EPA methods that are in draft or to be approved. The approved methods are categorized as: general-purpose, industry-specific, and Whole Effluent Toxicity (WET). General-purpose methods, also called 304(h) or part 136 methods, are the methods used for measuring pollutants in matrices including wastewater, such as EPA method 200.5, 200.7, 200.8, and 200.9 for general metal analysis and other methods for specific metals like mercury, platinum, and rhodium. Industry-specific methods are used for specific industry and listed in Part 136 Table IF and IG, and in part 401 to 503. There are no elemental analysis methods in this category. WET methods use organisms to test survival and reproduction changes upon application of the whole wastewater samples.