Odor Science -Part I- Environmental Management

Part One: Introduction to Odor Analysis, Measurement, and Odor Impact Study

A few months ago the manager of a large regional landfill said to me “What wasn’t an odor issue 20 years ago, now is. We have had to adapt to meet expectations of our host community and neighbors.”

Not only are tolerance levels with respect to odors changing, but there is an increasing need for more facilities that generate odor in their processes. These include anaerobic digesters, waste to energy operations where organic wastes are processed to produce methane gas for energy, sludge composting facilities making fertilizers, to name just a few. Success in securing local approvals to build an operate such facilities and maintaining long term good relations with host communities and neighbors requires a comprehensive odor management program that is well planned and executed.

The Maine Legislature recently passed a law that requires Maine DEP to establish additional odor rules. This law is very specific to operations that process or compost sludge from publicly operated wastewater treatment facilities. According to DEP that’s about 18 facilities in the state. The comment period for the new regulations drafted by DEP runs through December 6. The new regulations include frequency, intensity, duration, and offensiveness and attempt to make assessment, management, and compliance predictable for everyone.

The EOi450 Flux chamber (a.k.a Emission Isolation Flux Hood) is used to determine levels of emissions from solid or liquid surfaces.

Part One

Throughout the world, odors are recognized as a significant environmental issue. The World Health Organization reports that odor complaints represent more than 70% of environmental issues, far exceeding noise and other forms of pollution. The public is not equipped with H2S gas detectors but everyone has a nose to smell!

This situation is not confined to developing countries. Throughout North America, potential odor emissions coming from wastewater treatment and composting facilities are facing widespread opposition from the public. New projects are systematically challenged, especially during the public review and local approval processes. Even worse, because of the lack of appropriate legislation, existing plants are experiencing an increasing number of class action suits and other legal actions directly linked to odor annoyances!

For more than fifteen years, Olfacto Expert members have represented owners of many industrial and other odor generating facilities in Europe and Canada at trials and class actions in this specific field of odors. Olfacto Expert has also worked with the public sector and assisted in the establishment of odor regulations for municipalities and governments. From these experiences and through thousands of odor impact studies, Olfacto Expert believes that it is absolutely necessary to establish some appropriate limits in terms of gravity, duration and frequencies of any odor perceptions so that project owners, abutters, host communities, and regulators are all working off the same standards; however, we need to define the tools needed to establish such limitations and evaluations:

Sampling in the clouds: More and more WWTP are now equipped with stacks to help odor dispersion

Odor Diagnosis

This essential step samples odor at their sources and through olfactometric analysis determines the hierarchy between sources, therefore determining the priority for any future potential reduction.

Olfactometric Analysis

The Olfactometric analysis provides odor quantification of odor concentration. This analysis is governed by the American standard ASTM E679-91 and European standard CEN13725 which establish laboratory quality conditions and standards for analyses features including air quality used during analyses, certification of individual odor threshold for each panelist during a three week period, ambient air quality control in the lab, cleaning as well as contamination measures, etc.

Odor Impact Study – (OIS)

OIS uses previous odor concentrations (in odor unit per cubic meter: O.U./m3 or Dilution per Threshold: D/T) and odor flow rates (in odor unit per square meter and per second: O.U./ m2/s). An OIS produces accurate and objective results that are graphically displayed and mapped. The study provides hard data and information needed to assess and map the olfactory disturbance impacting a population; including odor concentrations (first maxima), duration, and frequency (Percentiles 95, 98 and 99.5). Odor impact studies utilize designs and proposed operations along with real weather data for a proposed site to develop odor mitigation planning into a new facility and assure the public that odor management is important to the project owner.

Odor Measurement

Technology and science have made it possible to quantify odors. Consequently it is possible to establish appropriate objective regulations based on odor perceptions after dispersion rather than odor emissions. To implement an odor management plan at a facility or to validate any odor complaint by municipal or state inspectors, Olfacto Expert’s team has developed emetrics® including an ultra-portable Odormeter, which lets owners, regulators, and inspectors measure at the fence line. One odor unit is the perception threshold: 1 O.U./m3 (or D/T)

3 O.U./m3 (or D/T) is considered the “recognition threshold”, meaning 3 persons out of 6 (50%) will be able to identify the source of odors butnone of them would likely complain at such level;

5 O.U./m3 (or D/T) concentration, also named “frank recognition”, meaning 6 persons will be able to identify the odor, and, depending on aggressiveness, one of them would likely complain at that level;

11 O.U./m3 (or D/T) concentration is internationally recognized as the first complaint level.

Owners and operators of WWTPs, compost facilities, waste to energy operations, as well as host communities, abutters, and regulators respect the science and technology behind this ability to accurately measure odor, including the frequency and gravity of the emissions. Sensible concentration levels can be appropriately chosen, taking into account important features including local topography, odor aggressiveness and above all distance to the first neighbors … but this will be addressed in part 2.