Maine DEP Finalizes New Odor Regulations

Maine facilities that compost or otherwise process wastewater solids and septage will have to follow new, strict odor standards in early 2015 when new provisions take effect.

In early June, the ME Department of Environmental Protection (DEP) released its formal rule adoption package, including the full text of the updated rules, for Chapter 410 - composting facilities and for Chapter 409 - other processing facilities.  The new rules adopt the n-butanol scale for odor measurement (see the sections titled "Odor Control" (section 4F in Ch. 409 and section 4E in Ch. 410)).

Malodors are widely considered the primary cause of public upset around biosolids and septage management programs.  Regulations addressing odors are a double-edged sword.  They make it more difficult and costly to recycle these materials.  But, at the same time, they may ensure significant malodors don't happen and cause the kind of public upset that shuts down a program.

The change in how Maine DEP is addressing odors is dramatic. The former requirements for odor control were, simple, as follows:

(a) The facility must be operated to prevent nuisance odors at occupied buildings.

(b  Facility personnel must immediately contact the Department to report odor complaints received by the facility. The Department, after investigation, will determine whether the facility has caused a nuisance odor at an occupied building....

Beginning March 15th, 2015, facilities processing wastewater solids or septage will be subject to the following more specific and stringent requirements:

  • The facility may not create nuisance odor at or beyond the property boundary.
  • The Department is given considerable leeway to define if an odor constitutes a nuisance and to require additional evaluation of odor issues by the facility operators.
  • A five-point odor intensity scale will be applied to odors.  The scale uses n-butanol concentrations in water as a reference.  An odor - even if short-term - with an intensity score of 4 (equal to 1200 ppm n-butanol) or greater automatically constitutes a nuisance.  Lower intensity odors for longer duration may constitute a nuisance, based in the Department's judgement. 
  • A facility can use an alternative odor measurement technology, if they demonstrate that it provides equal or superior performance.
  • The Department will forgive temporary odor issues under particular circumstances detailed in the regulation.

The new odor standards also spell out specific procedures a facility must follow in response to the potential of a nuisance odor, including evaluation of the odor event and submission of specific information to the Department, which may then require a more thorough odor management plan.  Another section of the rule specifies the details of such a plan.

The adoption package released by DEP includes responses to comments received during public review of the proposed rule changes.  DEP indicated that some parameters were changed in the final rule, based on comments, including:

  • changing the minimum threshold for defining a nuisance odor from an odor intensity score of 1 to a score of 2 for 60 minutes or more
  • allowing for alternative odor measurement systems
  • removing mention of odor annoyance, since the n-butanol scale being used is only a measure of odor intensity

NEBRA and others had also critiqued the technical reliabilty of the n-butanol scale.  DEP responded that, while lab and odor panel evaluations of odors might be preferred, the n-butanol reference scale is a practical system for use in the field.  "By its very nature, the perception of odor is subjective." The rules, they say "represent the Department’s best effort to quantify something that is very difficult to quantify."  

NEBRA also questioned the fairness of the rules targeting only wastewater solids and septage, even though processing other organics can create similar odor nuisances.  DEP said that its directive was to address only wastewater solids and septage in the new standard.   Processing other organics will continue to have to comply only with the simpler existing odor requirements quoted above.

DEP's responses emphasized that "composting and septage processing facilities should take a proactive approach to odor management that includes, in part, evaluating potential process odors, implementing methods to prevent nuisance odor, periodically monitoring for facility odor and responding to odor complaints in a timely manner. This type of odor management allows for the prevention and control of odor during routine operations so that a determination of nuisance odor is unlikely."