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February 6, 2019  |  Written by Alyson E. Ackerman

South Coast Air Quality Management District Unanimously Grants a Regular Variance to City of San Bernardino Municipal Water Department

Recently, the South Coast Air Quality Management District (SCAQMD) unanimously granted the City of San Bernardino Municipal Water Department’s (Department) request for a variance from a SCAQMD rule mandating reduced emissions from several internal combustion engines (ICEs)  that are used at the Department’s wastewater treatment plant (Plant).  The Hearing Board for SCAQMD granted the variance for five digester gas-fueled ICEs, which directly drive process equipment and power generation equipment at the Plant.  The variance commenced at the conclusion of the hearing on December 20, 2018, and the Hearing Board issued its final Minute Order and Findings and Decision on January 29, 2019.  The variance relieves the Department from imposition of civil penalties during implementation of the Digester Gas Beneficial Use Program (DGBU Program), which is scheduled for completion by September 1, 2021.  When completed, the DGBU Program continues the beneficial use of digester gas produced in the Plant’s treatment processes through new, innovative means, and once completed, will bring the Department in compliance with Rule 1110.2’s emissions limits.  Further, the funding for the DGBU Program does not require a rate increase, despite extensive and complex changes to the Plant’s facilities that are necessary to support the DGBU Program.

The Plant

The Department provides wastewater collection and treatment for the City of San Bernardino and two “satellite” sewer collection systems operated by the East Valley Water District.  The Plant is a secondary treatment facility receiving and treating approximately 21.5 million gallons of influent each day. The Plant uses an activated sludge process to treat the liquid wastewater stream, and an anaerobic digester process to treat, break down, and stabilize the sludge generated throughout the treatment processes.  A byproduct of anaerobic digestion is digester gas, which contains methane.  Currently, digester gas is captured and utilized throughout the Plant to fuel ICEs that drive blower motors, pumps, and power generation equipment critical to the Plant’s processes.

Rule 1110.2

SCAQMD Rule 1110.2 limits Oxides of Nitrogen (NOx), Carbon Monoxide (CO), and Volatile Organic Compounds (VOCs) emissions from gaseous and liquid-fueled ICEs.  In September 2012, amendments to the Rule brought biogas-fueled ICEs within its purview, forcing owners and operators of such ICEs to meet Rule 1110.2 emissions limits by a certain date.  SCAQMD identified Selective Catalytic Reduction (SCR) as the Best Available Control Technology (BACT) to meet the Rule’s emissions limits.

Technology Demonstration

Due to space, operational, and cost constraints, the Department could not use SCR at the Plant.  With SCAQMD’s approval, the Department engaged in a demonstration project to provide an alternative to BACT for medium-sized wastewater treatment facilities, like the Plant.  The alternative was projected to be both cost-effective and successful at achieving emissions below the Rule’s emissions limits (without gas pretreatment or exhaust post-treatment).  If successful, the demonstration project would also allow for continued beneficial use of digester gas to drive and power equipment throughout the Plant.  Initially, the Department served simply as a host site for the demonstration project, but it became a primary funding and technical support resource.  Ultimately, because of the looming compliance deadline, the demonstration project was not a viable alternative for the Plant.

Path to Compliance

The Department studied and evaluated alternatives for continued beneficial use of digester gas at the Plant, such as Cogeneration with Heat and Power (CHP) with microturbines, CHP with fuel cells, and even digester gas conversion to renewable natural gas for pipeline injection, among others.  After balancing its customers’ needs and its leadership role in the regulatory environment, the Department determined that fuel cell technology is the most manageable compliance alternative with the least financial impact on the Department’s ratepayers.

Implementation of the fuel cell project requires construction of “resultant projects,” all of which comprise the DGBU Program.  The specific projects of the DGBU Program include the following:

  1. Fuel Cell Project
  2. Blower Electrification Project
  3. 0.025 Duty Flare Project
  4. Digester Gas Storage Project
  5. Arrowhead Lift Station Electrical Supply Project
  6. Arrowhead Lift Station Pump
  7. Electrification Project
  8. Arrowhead Lift Station Pump Conversion Project
  9. 0.06 Back-up Flare Project

The DGBU Program will cost an estimated $13 million to complete, and is currently fully funded.  Once the DGBU Program is implemented, the Plant will comply with Rule 1110.2, and will be able to continue to use digester gas produced throughout the treatment process to offset the Plant’s energy needs.

Variance Granted  

The Hearing Board unanimously granted the Department’s variance after it concluded that the Department satisfied the six findings necessary to support a regular variance.  The Department’s variance is subject to conditions and increments of progress, which are the product of collaboration with SCAQMD Staff and Counsel.  Both the conditions and increments of progress serve as milestones for the Department to demonstrate its progress towards achieving compliance by September 1, 2021.

A full copy of the Findings and Decision of the Hearing Board is available here.  The Minute Order is available here.

For additional information on petitions for variance and air quality issues, please contact Alyson E. Ackerman at or 916-469-3843, or Michael E. Vergara at or 916-469-3824.

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