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Pacific Southwest, Region 9

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

Evoqua Water Technologies

Air Emissions

Note: Evoqua Water Technologies has previously been known as Siemens, US Filter, and Westates. The facility is now referred to as Evoqua, but the prior names remain in older documents attached to this web page.

What Are the Human Health Impacts From Air Emissions?

Evoqua Stack Gas Composition
  • 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, Evoqua 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, Evoqua conducted a test of the regeneration furnace (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 2016 Evoqua Human Health and Ecological Risk Assessment (HHERA) Risk Assessment fact sheet (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

The following are links to the trial burn (also known as the Performance Demonstration Test) plan and report done at the request of EPA. These documents helped Evoqua develop proposed operating parameters for the facility.

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