Nine Springs Wastewater Treatment Plant 2020 Energy Management Master Plan

The wastewater industry is rapidly transforming into an energy-efficient and energy-producing business. Utilities across the country are departing from energy-intensive processes in favor of innovative approaches that recover clean water and nutrients while creating renewable energy for their communities.

Supported by our nationwide Carbon and Energy Management Innovation Initiative, Carollo is tackling today’s energy challenges by leading a growing number of energy management and renewable energy planning and design projects. One such effort is our development of the Madison Metropolitan Sewerage District’s (District’s) 2020 Energy Management Master Plan at their Nine Springs Wastewater Treatment Plant (NSWWTP), a comprehensive roadmap that recommends targeted improvements to the Wisconsin-based utility’s energy infrastructure and energy-management approaches over the next two decades.

The master plan was born out of the District’s need to replace aging energy-producing and energy-consuming infrastructure at the NSWWTP—an effort with an estimated life-cycle cost of $93 million without explicit process or energy performance improvements. To make strategic use of these investments, the District decided to pursue improvements that not only rehabilitate the NSWWTP’s existing infrastructure but also meet the following energy goals by 2030:

• Reduce fossil-fuel-based greenhouse gas emissions by 10 percent
• Reduce the cost of peak electricity demand by five percent
• Reduce operational energy consumption by 10 percent
• Use renewable energy to meet 50 percent of energy demands
• Reduce Class B biosolids processing energy demand
• Improve the resiliency and reliability of energy supply sources
• Improve the reliability of energy-using and energy-consuming infrastructure

In collaboration with the District, Carollo convened an industry-wide energy expert panel that identified numerous technology and energy concepts, which were grouped into six major improvement categories—co-digestion, biosolids, biogas, thermal, renewable energy, and effluent pumping. Using a systematic screening process, Carollo and the District then pared down these concepts into two final recommended alternatives using the District’s specific evaluation criteria, which included energy efficiency, resilience, reliability, cost, and operation and maintenance.

Following thorough business case evaluations and sensitivity analyses, Carollo recommended that two scenarios be further evaluated against the Baseline Scenario. Both Alternatives 1 and 2 replace the NSWWTP’s aging energy infrastructure and beneficially use all biogas produced for either on-site electricity generation or renewable natural gas production at life-cycle costs similar to or lower than that of the baseline.

Of the two, Alternative 1 is appealing in that it maintains the District’s current operational philosophy (i.e., cogeneration and renewable electricity production) and robustly meets all seven of the Plan’s energy goals. Alternative 2 offers a lower life-cycle cost, simplified infrastructure, and lower operational complexity but does not meet the District’s goal of reduced peak demand costs since it converts biogas to renewable natural gas rather than on-site electricity. However, this scenario promises high revenues following the value of renewable identification numbers in the Environmental Protection Agency’s Renewable Fuel Standard program. In fact, revenues from renewable natural gas sales are projected to offset this scenario’s increased costs in peak energy demand.

One particular challenge included aligning project objectives from various departments and the District’s governance for infrastructure evaluation. Carollo addressed this issue through careful planning of meeting attendance, interactive workshop activities/polls, clear meeting minutes, and decision documentation. In an effort to identify and prioritize the universe of the District’s preferred alternatives, the Carollo team hosted invited expert workshops to brainstorm options and subsequent application of tiered, transparent, and weighted selection criteria to select the preferred alternatives.

The District will engage stakeholders and community partners to further assess the final two recommended alternatives and earn public support for an effective, responsible, and transparent infrastructure project that delivers sustainable benefits in the long term.