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Summary

On June 14, 2017, EPA final ruling, 40 CFR 441 (Effluent Limitations Guidelines and Standards for the Dental Category), concerning standards and best practices for effluent dental water was published in the federal register. The ruling has mandated the use of an amalgam separator, established best management practices (BMPs) prohibiting the use of oxidizers in dental effluent water, and requires a one-time certification of compliance for those subject under it. 

 
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The ruling prohibits discharging amalgam waste into public water sewage and subsequently mandates the use of an amalgam separator. The ruling specifies that the separator must comply with the ISO standard 11143 and maintain 95% of solids to meet that standard. Since the dental industry alone is releasing about 5 tons of mercury-containing amalgam into the sewage systems, the EPA has included this requirement in the ruling for the betterment of the environment. 

 

 
 

The waterline cleaner BMP forbids the use of oxidizing waterline cleaners in “dental unit water lines, chair side traps, or vacuum lines that lead to an amalgam separator. Oxidizing line cleaners have been shown to contribute to the solubilization of mercury into public works. The ruling goes into further detail stating oxidizing line cleaners, “including but not limited to, bleach, chlorine, iodine and peroxide, that have a pH lower than 6 or greater than 8,” must not be used to treat dental waterlines. 

 

 
 

"For existing sources, a OneTime Compliance Report must be submitted to the Control Authority no later than October 12, 2020, or 90 days after a transfer of ownership. For new sources, a One-Time Compliance Report must be submitted to the Control Authority no later than 90 days following the introduction of wastewater into a POTW."

As defined in § 441.50, the compliance report will essentially enforce the Pretreatment Standards for Existing Sources (PSES) and the Pretreatment Standards for New Sources (PSNS).

The PSNS and PSES dictates the following:

  • “Removal of all dental amalgam solids from all amalgam process waste water…” as described in § 441.30.
  • Implementation of BMPs which include the prohibition of oxidizing line cleaners in dental unit waterlines that discharge into public works.

As part of the report, those subject under the ruling must certify they are “implementing BMPs specified in § 441.30(b) or § 441.40(b) and will continue to do so.

 

 
 

"The final rule is effective on July 14, 2017. The compliance date, meaning the date that existing sources subject to the rule must comply with the standards in this rule is July 14, 2020. After the effective date of the rule, new sources subject to this rule must comply immediately with the standards in this rule." 

 

The EPA ruling published to the federal register can be found in full here: 


WHY YOU SHOULD NOT USE OXIDIZING LINE CLEANERS

 

Sterisil Straw V2 - EPA Compliant waterline disinfectant for 365 days

 
 

Analysis


The rule establishes clear requirements for all parties and compliance with the final rule is simple and straightforward for dental offices and the regulating authorities. It requires dental offices to install and operate a separator, to implement two BMPs, and to submit a One-time Compliance Report to the Control Authority.
— Pg. 27165

The Role of the Amalgam Separator

Mercury from dental amalgam in wastewater is present in both the particulate and dissolved form. The vast majority (>99.6 percent) is particulate (DCN DA00018). An additional process sometimes referred to as ‘’polishing” uses ion exchange to remove dissolved mercury from wastewater. Dissolved mercury has a tendency to bind with other chemicals, resulting in a charged complex. Ion exchange is the process that separates these charged amalgam particles from the wastewater. For ion exchange to be most effective, the incoming wastewater must first be treated to remove solids. Then the wastewater needs to be oxidized (creating a charge on the amalgam particles) in order for the resin or mercury capturing material to capture the dissolved mercury. Therefore, ion exchange will not be effective without first being preceded by a solids collector and an oxidation process. The data available to EPA indicate that total additional mercury reductions with the addition of polishing are typically about 0.5 percent (DCN DA00164).
— Pg. 27160

Since Mercury is present in the dental waterline in both solid and dissolved form, the use of an amalgam separator accounts for 99.95% of the removal process. Most amalgam separators focus on removing solids but there is a recent push to develop separators with ion exchange capabilities to capture dissolved mercury. 


Restrictions on Oxidizing Line Cleaners

 
Dental unit water lines, chair-side traps, and vacuum lines that discharge amalgam process wastewater to a POTW must not be cleaned with oxidizing or acidic cleaners, including but not limited to bleach, chlorine, iodine and peroxide that have a pH lower than 6 or greater than 8.
— Pg. 27178
In addition to technologies, EPA also identified best management practices currently used in this industry (and included in the ADA BMPs) to reduce dental amalgam discharges. In particular, EPA identified two BMPs to control dental amalgam discharges that would not be captured by an amalgam separator and/or polishing unit. Oxidizing line cleaners can solubilize bound mercury. If oxidizing cleaners are used to clean dental unit water lines, chair side traps, or vacuum lines that lead to an amalgam separator, the line cleaners may solubilize any mercury that the separator has captured, resulting in increased mercury discharges. One BMP ensures the efficiency of amalgam separators by prohibiting use of oxidizing line cleaners including but not limited to, bleach, chlorine, iodine and peroxide, that have a pH lower than 6 or greater than 8.
— Pg. 27161
Mercury being a metal leaves it extremely susceptible to oxidization and conversion into a liquid once it is trapped in the amalgam separator.

Mercury being a metal leaves it extremely susceptible to oxidization and conversion into a liquid once it is trapped in the amalgam separator.

Line cleaners defined as “oxidizers” according to the ruling can increase the mercury content going into the municipal supply and therefore should not be used in accordance with this ruling.

Line cleaners defined as “oxidizers” according to the ruling can increase the mercury content going into the municipal supply and therefore should not be used in accordance with this ruling.

The ruling specifies that oxidizing line cleaners, specifically bleach, chlorine, iodine, and peroxide, that have a ph lower than 6 or greater than 8 are not to be used. 

The ruling specifies that oxidizing line cleaners, specifically bleach, chlorine, iodine, and peroxide, that have a ph lower than 6 or greater than 8 are not to be used. 


One-time Compliance Report

(1) One-Time Compliance Report Deadlines. For existing sources, a One-Time Compliance Report must be submitted to the Control Authority no later than [INSERT DATE 3 YEARS AND 90 DAYS AFTER THE EFFECTIVE DATE OF THIS RULE] or 90 days after a transfer of ownership. For new sources, a One-Time Compliance Report must be submitted to the Control Authority no later than 90 days following the introduction of wastewater into a POTW.

(2) Signature and Certification. The One-Time Compliance Report must be signed and certified by a responsible corporate officer, a general partner or proprietor if the dental discharger is a partnership or sole proprietorship, or a duly authorized representative in accordance with the requirements of 40 CFR. § 403.12(1).
— Pg. 27178
 

Under the ruling, an existing practice will have until July 14, 2020 to install an amalgam separator, comply with the pretreatment BMP's, and submit their one-time compliance report. Newly constructed offices and offices that transfer ownership will have 90 days from the introduction of waste water into the public water supply.


Regulatory Overlap

 

At the time of publication, there are 12 states and 18 municipalities that already have programs in place to prevent mercury discharge. This final ruling will take precedence over any existing local code or requirements while preserving any addition requirements beyond the scope of the EPA ruling. 

Some proposal commenters, many of whom are in states and localities with existing programs, questioned the application of this rule to dentists already subject to state and local programs noting the duplicative requirements. While EPA found that many of the existing programs contained at least one attribute of this final rule (e.g. separators, reporting, BMPs, operation and maintenance), the majority did not contain all of the attributes. Generally, the additional requirements (and associated costs) of this final rule are incremental over existing mandatory state or local dental amalgam reduction requirements. For example, a dentist located in a state or locality that does not require one or both of the BMPs specified in this rule must implement both BMPs.
— Pg. 27164