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Pacific Southwest, Region 9

Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations

Evoqua Water Technologies
(formerly Siemens Carbon Regeneration Facility)


Air Emissions

What are the human health impacts from air emissions?

Evoqua Stack Gas Composition (Typical):

  • 49.2% Steam
  • 42.2% Nitrogen
  • 4.7% Oxygen
  • 3.9% Carbon Dioxide
  • 0.006% Other
    • 0.005 Nitrogen Oxides
    • 0.00023% Hydrogen Chloride and
    • 0.0002% Carbon Monoxide
    • 0.00007% Ash
    • 0.0000004% Metals
    • 0.0000005% Organics (estimated)
    • 0.0000000000001% Dioxins

At EPA’s request, and as part of the permit process, the Evoqua Facility completed a human health and ecological risk assessment in July 2007.  The purpose of the risk assessment was to estimate the Evoqua Facility’s current and possible future impacts on the health of local residents and the surrounding environment.  Based on the risk assessment study,  EPA concluded that human health impacts from long-term exposure to stack emissions, fugitive emissions, as well as the combination of the two, were below EPA’s acceptable thresholds. 

Stack emissions: To measure stack emissions, the Evoqua Facility conducted a trial burn under specific operating conditions (e.g., temperature of the furnace, amount of carbon being processed by facility, contaminants present in the spent carbon).  The concentrations of contaminants coming out of the stack were measured during the trial burn (see the box at right).  Computers helped model how emitted substances would disperse (spread) throughout the air and soil in a 154 square mile area surrounding the facility.

Fugitive emissions: Fugitive emissions are generated during unloading of the spent carbon that comes into the Evoqua Facility (see Figure 2 in the Risk Assessment fact sheet - Evoqua HHERA fact sheet March 2015 (PDF) (2 pp, 272K) The risk assessment determined levels of fugitive air emissions from information on amounts of spent carbon that Evoqua handles, as well as the concentrations of contaminants in that spent carbon. 

Appendix V of the permit: Performance Demonstration Test Plan and Report

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more about PDF, and for a link to the free Adobe Reader.

The following are links to the Performance Demonstration Test plan and report done at the request of EPA.  These reports help determine operating parameters for, and emissions limits from, the Evoqua facility.

Evoqua Contact Information

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