Project Number:

1437

Metropolitan Milwaukee Sewerage District (MMSD)

SERVICE:

Air Permitting for Municipal Sludge Dryers

DESCRIPTION:

The Metropolitan Milwaukee Sewerage District's (MMSD) Jones Island Wastewater Treatment Plant is located south of downtown Milwaukee and is one of two plants treating sewage for 1.2 million people in the Milwaukee metropolitan area. The­ facility is equipped with direct-fired municipal sludge dryers. The facility received a Notice of Violation because its emissions were exceeding the permit limits for volatile organic compounds (VOCs) and hazardous air pollutants (HAPs).

Further scrutiny revealed that the initial permitting only accounted for emissions from wastewater operations, and did not account for the VOC and CO output from sludge drying. Consequently, re-permitting was required, and a "net emissions" approach was chosen in order to demonstrate that the increase was less than or equal to 24 tons per year. The facility's engineering firm believed that the facility already had sufficient data on hand to justify this permitting approach.

The MMSD retained Tech Environmental to examine the test data and ensure that all sources would be properly addressed in a future permit. The goal was to extrapolate the potential increase from current test data. Tech evaluated the data and recommended that the sampling procedure be modified and improved to more accurately reflect existing conditions. Tech also made recommendations to help the facility improve its emissions estimation, permitting strategy and compliance reporting procedures.

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Key Points

  • The Metropolitan Milwaukee Sewerage District required air permitting assistance for one of their two large municipal sewage facilities.
  • Tech reviewed modeling, analysed data, and made recommendations that allowed the permitting process to proceed.