Recently I attended Kentucky/Tennessee Water Professional Conference in which the Dental Amalgam Rule was discussed during the Pretreatment Session. In this month’s blog post, I wanted to give you background and an update on the Dental Amalgam Rule.


Mercury, being a persistent bio-accumulative toxic element, is a concern to human health.  Fish and shellfish convert it to methyl mercury that, through consumption, can harm the nervous system of fetuses, infants and children. A study conducted in 2003 estimated that 50% of mercury entering the POTWs was contributed by dental offices. Dentists discharge approximately 4.4 tons of mercury each year to POTWs. Mercury containing amalgam wastes find their way into the environment when new fillings are placed or old mercury-containing fillings are drilled out. Waste amalgam materials are flushed into chair-side drains which enter into wastewater stream and some of the particles settle out in the sewers while some are carried to POTWs. POTWs remove about 90% of mercury which then resides in the biosolids or sewage sludge generated during primary and secondary treatment processes.


EPA proposed pretreatment standards in October 2014 for discharges from certain existing and new dental practices. The Final Rule is anticipated to be out in December 2016.


(1) Removal of at least 99% of total mercury from amalgam process wastewater

(2) Incorporation of BMPs such as:

  • Chair-side traps that may drain to a sewer must be cleaned at least weekly with non-bleach, non-chlorine containing cleaners.
  • Facilities must install at least one 2008 ISO 11143 certified amalgam separator.
  • Scrap amalgam may not be flushed down the drain.

(3) Performing Baseline Monitoring for existing sources within 180 days and new sources within 90 days.

(4) Installation of separators prior to the proposed rule signature would mean that the dentists satisfy the requirements for 10 years if they continue to meet the requirements as specified in the rule.

(5) Submitting a 90 Day compliance report and a periodic monitoring report.

(7) Maintaining records for three years from the date they are created.

(8) If the dental discharger complies with the requirements in 40 CFR 403 and 441, discharger may be considered as Dental Industrial User (DIU) otherwise the Control Authority (CA) must treat the discharger as a Significant Industrial User (SIU).

(9) CA must evaluate, at least once per year whether DIU still meets the criteria under 40 CFR 441.60.

(10) In accordance with 40 CFR 403.8(f)(2)(viii)(F), a DIU is in significant non-compliance if it fails to provide any required report within 45 days of the due date or if the CA elects to inspect the facility and finds the facility is not in compliance with 40 CFR 441.60 . If DIU has not returned to compliance within 90 days, CA must treat the dental discharger as a SIU.

Please contact me if you have any questions in regards to this rule.

In my next blog, I will come back to the Local Limits Review and Re-evaluations.


Shri Vani Sripada is a Project Engineer at Smith Management Group. Shri Vani can be reached at