Not all of the scrap amalgam and particulates are captured by the chair-side traps and vacuum filters. Grinding, drilling, and polishing of amalgam fillings may result in the production of fine particulate matter that passes through the chair-side traps and vacuum filters (Nimmo et al., 1990, Brune et al., 1980). The residual particulates remain in the wastewater discharged to the sanitary sewer.
An additional source of mercury is wastewater from instrument washing, and chair-side trap and vacuum filter cleaning. This wastestream may not be managed by a device designed to capture amalgam.
A practical type of treatment is amalgam separators used to remove amalgam waste and particulates from wastewater prior to discharging to the sanitary sewer (see the Naval Dental Research Institute's website for the American Dental Association's evaluation of available amalgam separators).