The City of Southlake has an approved pretreatment program in coordination with the Trinity River Authority (TRA), where our wastewater is eventually treated. Commercial and industrial facilities utilize pretreatment of wastewater to remove harmful pollutants before they are discharged to the wastewater system under the control of a publicly owned treatment works (POTW).
In the City of Southlake, the control authority for this program is the Trinity River Authority. The pretreatment program is required by the United States Environmental Protection Agency (US EPA) and approved by the Texas Commission on Environmental Quality (TCEQ).
The Environmental Protection Agency has put into effect pretreatment standards under the Clean Water Act to reduce discharges of mercury from dental offices into publicly owned treatment works. More information on the Dental Effluent regulation can be found here. New dental offices that began operating after July 14, 2017 are required to immediately comply with the rule. Dental offices that existed before July 14, 2017 must comply by July 14, 2020.
Why is this required for dental clinics?
The main source of mercury discharges to POTWs are dental clinics. Mercury-containing amalgam wastes may find their way into the environment when new fillings are placed or old fillings containing mercury are drilled out. Waste amalgam materials that are flushed into chair-side drains enter the wastewater stream. Mercury entering POTWs frequently splits up into the sludge, the solid material that remains after wastewater is treated. Mercury from waste amalgam therefore can make its way into the environment from the POTWs through incineration, landfillings, land application of sludge, or through surface water discharges.