Innovative Application of OTM-10 Using Open Path FTIR to Measure Mass Flux by Vertical Radial Plume Mapping

Client/Industry Overview

A confidential client that operates a chemical manufacturing facility came to Spectrum to assess and measure potential in-plant emissions from several wastewater collection sumps and pits.  These wastewater collection areas receive various process water streams containing highly variable concentrations of different Hazardous Air Pollutants (HAP) compounds of interest.  In order to demonstrate its sustained Synthetic Minor Source Status, the client wanted to not only monitor ambient air concentrations, but also use the USEPA’s OTM-10 approach to quantify the total mass flux of speciated HAPs from these pits and sumps.

Since 2006, OTM-10 has been an approved FTIR technique used by the Environmental Protection Agency (EPA) to assess a wide variety of area sources, including landfills, agricultural activities such as pits and lagoons, as well as other industrial fugitive-type emissions. The approach can be used in either a horizontal or vertical fashion, and in this case, we used the Vertical Radial Plume Mapping (VRPM) approach.



The facility has been historically considered a Synthetic Minor Source for Hazardous Air Pollutants under its local air permitting program. In an effort to estimate its wastewater-related air emissions, the facility began using a variety of software tools including the EPA’s Water9 model, as well as other commercial packages.  These are generally steady-state calculation tools that commonly predict uncharacteristically high total-annual mass emissions, that in this case exceeded the site’s minor source status. 

Due to the highly dynamic state of wastewater generation and material usage, the client wanted Spectrum to perform long-term studies over a wide variety of their operational modes.  The plant site was very compact and required sampling equipment to remain “out of the way” – hence, the open-path approach. 



Many critical elements go into the successful design, development, and execution of multiple week-long field sampling programs.  The client, the local agency, and a variety of consultants as well as the site’s operational staff all played a critical role in the project’s success. 

Our team deployed our WaveRunIR-OP FTIR, situated atop an auto tracker, to make use of five separate retro arrays covering the necessary pathways, in an effort to collect many hours of downwind plume data.  Spectrum arranged the mirrors atop a simple scissor-jack work platform to make use of three 3-D sonic anemometers, as we believe that properly characterizing the wind field is just as critical as knowing the ambient concentrations.  After ensuring all of the operational modes for each particular collection sump were adequately captured, Spectrum relocated its equipment to the next wastewater sump. 

Our team of experts have developed a software package within NuWave™ to provide real-time emissions flux data every five minutes.  As the wind caused the emissions from the wastewater pits to pass through the “optical fence”, Spectrum was able to calculate in near-real-time emissions on an mg/sec basis.  Applying these dynamic emission rates to the duration of time associated with the range of operational activities, one is able to create an emissions profile for each wastewater sump unique to those activities and VOCs/HAPs being discharged to it.  

Spectrum Environmental Solutions was able to provide this special client with a very unique tool to address their unusual wastewater configuration.  We were able to perform the study in the midst of their ongoing daily activities.  Spectrum’s software provided OTM-10 compliant results instantaneously. 


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