In 2019, the landfill was required to provide a new pretreatment system to address the landfill’s wastewater (leachate) and reduce odors as a prerequisite to discharge to the municipal utility sewer system. We were engaged to devise and design a solution, and provide support during procurement and construction.

Our approach

Through laboratory and on-site pilot tests, we confirmed that biologically active aerated treatment is effective for controlling odors and scale-formation in the landfill’s leachate.

Using the design criteria developed during the pilot test, we prepared detailed design documents for construction of the full-scale leachate pretreatment facility and approximately 1.5 miles of gravity sewer for discharge to the municipal utility sewer system. The leachate pretreatment system includes a 1.8-million-gallon bioreactor within a secondary containment structure, jet aeration system sized to provide 30,000 pounds per day of oxygen, a wet surface air cooling system for cooling of mixed liquor during summer months, and an equipment building for electrical gear, chemical systems and cooling system recirculation pumps.

We prepared cost projections at each stage of design development and worked with interested general contractors at 30 percent, 60 percent and 90 percent design stages to solicit input regarding constructability and construction costs. We supported the landfill owner in direct procurement of major equipment packages, including the bioreactor tank structure, jet aeration system and wet surface air cooling system. We also provided construction engineering services for the leachate pretreatment system and gravity discharge sewer, including shop drawing review and on-site inspection services. 

Upon construction completion in 2022, we delivered on-site commissioning and start-up services and performed six manhole headspace testing events over a period of three months to confirm that leachate discharged from the new leachate pretreatment system had no significant impact on the utility’s collection system or water reclamation facility. A comprehensive operation and maintenance manual was prepared for use by the landfill owner’s operating staff.

Schedule optimization through collaborative delivery

  • Our regular engagement with contractors throughout the design development accelerated the bidding process since contractors were already familiar with the scope of work.
  • We solicited budget costs for major equipment packages early in the design process and incorporated shop drawing information into the design, thereby reducing construction-phase design changes.
  • We supported the landfill owner in early procurement of the long-lead, major equipment packages to reduce the construction schedule.  

This approach increased contractor understanding of the project, benefited the design team through contractor design and constructability input, and benefited the landfill owner through early understanding of construction costs and seamless transition to the bid phase and construction. Major equipment and contractor costs and contractor schedule input yielded an accurate project budget and expected cash flow.

Innovation adoption through stakeholder engagement

  • We demonstrated the unique biological treatment technology on a bench and pilot scale, assuring regulatory agencies the pretreatment system would be effective in meeting treatment objectives for the high-strength and challenging leachate matrix. 
  • We supported installation of a 5,000-gallon on-site bioreactor and oxygen-supply system and provided daily operation and maintenance. The team collected raw and pre–treated landfill liquids samples and analyzed the samples for a variety of conventional pollutants and individual organic and inorganic constituents to demonstrate effectiveness of the biological technology in meeting pretreatment objectives.

The demonstrations helped to facilitate regulatory approvals with minimal comments or concerns.

Smooth permitting and approvals

  • We worked closely with the landfill owner and representatives of the municipal sewer authority during preparation of laboratory and pilot-scale work plans and test implementation.
  • We supported the landfill owner in preparation of compliance documents and permitting with the regulatory agencies (local sewer authority and state environmental regulatory agency), conducting meetings with the agencies at critical stages of project completion.

This collaborative approach minimized the permitting time after submittal of the permit-to-install application package.

Outcome

The new leachate pretreatment facility has enabled the landfill to discharge its leachate to the municipal sewer authority in consistent compliance with the requirements of the regulatory agencies.