Section 3: Water Releases

Wastewater Treatment by Chemical

This figure displays the types of wastewater treatment methods applied in 2013 to the chemicals for which water releases have declined at the fastest rate. Many TRI facilities treat a waste stream before release or transfer to reduce the quantities of chemicals that are ultimately released.

Different types of chemicals tend to undergo different on-site treatment methods. For example, metals (arsenic, zinc, nickel, and their compounds) in wastewater are most commonly treated by settling or clarification, whereas solids are removed using sedimentation techniques. While metals cannot be destroyed, they can be removed from the waste stream. Glycol ethers are more commonly treated using biological treatment, which is effective for some non-metals.

TRI facilities report the type and efficiency of waste treatment methods applied on-site to waste streams containing TRI chemicals. Facilities report all treatment methods that the waste stream goes through, even if the method has no impact on removing or destroying a particular chemical. For example, an aggregated waste stream containing metals and acids may go through a neutralization process, which destroys the acid but has no effect on the metals. In this case, neutralization would still be reported as a treatment method for the metal.

This page was published in January 2015 and uses the 2013 TRI National Analysis dataset made public in TRI Explorer in October 2014.