Meeting Process Planning Challenges: Advanced Wastewater Treatment for New York City

Client: New York City Department of Environmental Protection
Location: New York, NY

The NYC Department of Environmental Protection’s (DEP) Advanced Wastewater Treatment Program provides Design, Programmatic, and Process Planning services focusing on the attainment of future stringent Total Nitrogen discharge limits for Wastewater Treatment Plants that discharge to the East River and Jamaica Bay. In joint venture, Hazen and Sawyer is leading the effort to coordinate the ongoing $1.2 Billion of construction under the first phase of this program, provide design guidance and process planning modeling to assess the scope of needed upgrades for the second phase, and provide general process planning assistance to assist DEP plan for future treatment challenges.

Project Outcomes and Benefits

  • Provided design guidance that became the bedrock of DEP’s current Phase I BNR Construction Program.
  • Coordinates more than 30 ongoing construction contracts of an aggregate value of over $1.2 Billion to ensure compliance with interim Nitrogen stepdown limits.
  • Evaluates new technologies’ applicability to DEP’s programs and infrastructure.
  • Provides process planning assistance as potential new treatment regulations are discussed with EPA and other regulatory agencies.

DEP, DEC, and various constituent stakeholders have been working for years to curtail marshland loss and improve water quality in Jamaica Bay. The assessment of the performance and cost varying degrees of infrastructure enhancement for long-term studies such as EPA’s Harbor Estuary Program and Jamaica Bay Comprehensive Plan are core tenants of AWT’s work.

AWT assesses emerging technologies and their applicability to the New York City Nitrogen program. AWT recommended the installation of platform mixers (shown above) that accomplish the design objective of prevention of settling in anoxic zones at a fraction of the horsepower (and cost) of traditional submersible mixing units.

The prevention of Nocardia growth within treatment plants running the BNR process is a key operational challenge for DEP and AWT. Froth has the potential to damage DEP infrastructure and create an operational health and safety hazard for DEP personnel. AWT guidance implemented multiple lines of defense for froth control, including chlorination of the recycled activated sludge, surface wasting, and froth control hoods.

AWT has created a management tool called the Bulge that amalgamates individual treatment plants’ projected Nitrogen discharges at varying stages of construction. This tool allows DEP to quickly assess the performance, cost, and schedule impacts of potential modifications to the Nitrogen program. The Bulge allows AWT and DEP to take full advantage of new research and lessons learned from other municipalities in order to deliver to DEP world-class BNR treatment plants.

AWT wrote the design guidance that is the backbone of the $1.2 Billion Phase I BNR construction program that is currently underway. Baffles, mixers, tapered diffusion, and froth control provisions are among many enhancements to aeration tanks.

By 2017, the four Upper East River treatment plants need to reduce their current Total Nitrogen discharge by over 50 percent. AWT’s design guidance recommended Biological Nutrient Removal (BNR) as the City’s backbone technology for its Nitrogen program. However, the scope of upgrades provided under Phase I construction is insufficient to meet the final Nitrogen discharge limit; AWT is currently writing the Phase II BNR Facility Plan that will codify the scope of the second construction phase. Hazen and Sawyer will enable the DEP to implement the BNR process technology, achieve consent order completion milestones, and comply with future regulatory limits.

In addition to providing engineering and program management support to BNR upgrades currently underway, AWT is the vehicle by which DEP evaluates potential future treatment obligations. AWT frequently is asked to evaluate the appropriate technologies to comply with a possible future treatment obligation and provide a conceptual design and cost estimate. AWT also is asked to evaluate the impact of proposed changes to the input to DEP’s treatment plants. Recent examples include an assessment of the impact repealing a ban on commercial garbage grinders would have on DEP’s programs and infrastructure and an assessment of changed operating conditions at the Hunts Point WWTP once alum sludge residual from the Croton Water Treatment Plant once this facility is placed into service.

For more information on this project, or to discuss a similar project in your area, contact

Paul Pitt, Ph.D., P.E. at ppitt@hazenandsawyer