NEW Water (the Green Bay Metropolitan Sewerage District) was in need of new biosolids treatment facilities – located within the Green Bay Treatment Facility. This facility treats domestic waste in addition to paper mill waste. The Green Bay Treatment Facility was built in the 1970s, and has been in operation for over 40 years. The existing multiple-hearth furnace incinerator was considered “old and tired,” and no longer able to meet air permitting requirements. NEW Water, being on the cutting-edge of wastewater treatment, sought a partner who was likewise progressive and innovative.
The ultimate driver behind this project, known publicly as the Resource Recovery and Energy Project (R2E2), was NEW Water’s desire to save purchased energy costs, gain the ability to reuse nutrients, and make their treatment facility more energy self-sufficient in terms of creating electricity and heat. One of the primary tasks of wastewater treatment facilities is to remove nutrients from wastewater. Communities can either throw this byproduct away or reuse it.
For this project, it was NEW Water’s goal to both save energy and reuse nutrients by making fertilizer out of the byproduct.
NEW Water selected a consortium of consultants, specifically SEH to serve on the design team for these new biosolids treatment facilities. SEH’s role for the project, which was part of a $169 million effort, included new digestion, reciprocating engine electrical power generation, dewatering and incineration processes, and implementation of nutrient removal and recovery processes.
The SEH team helped NEW Water obtain an air permit for the new equipment and developed air permit compliance demonstration methods.
NEW Water becomes energy self-sufficient
The traditional wastewater treatment philosophy had been the following: treat the water, make the water as clean as possible, and do away with the waste byproducts. Conversely, the NEW Water plant is both progressive and proactive; the new design has made it possible for the plant to recover and reuse resources from the wastewater.
For example, with approximately 600 cubic feet of biogas per minute made by the digesters, NEW Water is now able to generate 70-80% of their electricity on-site as opposed to having to buy it from a power plant. Further, the fluid bed incinerator that was designed and installed has become a large source of heat. As a result, NEW Water is now reducing their purchase of natural gas by nearly 80%. In fact, during the winter months NEW Water can now heat the entire complex and buildings – all from waste heat generated by the engines and the incinerator.
Ultimately, by generating such significant amounts of electricity and heat, the Green Bay Treatment Facility is now almost entirely energy self-sufficient.
Digging into the technical components
The design team performed extensive alternative analyses for the new biosolids treatment facilities, which included multiple design workshops and collaboration with utility staff. The process train that was selected includes innovative features such as silo digesters, which are equipped to receive high strength waste (HSW). The team’s energy recovery system evaluation identified the most optimal solution to meet NEW Water’s economic and operational goals: engine generators and a gas conditioning system that consisted of an iron sponge for sulfide removal and additional siloxane removal vessels.
This project was all about recovering resources, making electrical energy, lowering the carbon footprint, and purchasing as few utility commodities as possible. In partnering with SEH and the other teams involved, NEW Water has taken significant strides toward regularly achieving these goals.
NEW Water Resource Recovery and Electrical Energy Project
Green Bay, Wisconsin
Green Bay Metropolitan Sewerage District (NEW Water)
- Mesophilic anaerobic digestion
- Biogas cleaning
- Electrical power generation
- Fluid bed incinerator
- Incineration with energy recovery
- Silo digesters equipped to receive HSW
- Struvite recovery system
- 70-80% electric and heat cost savings
- Wastewater engineering
- Mechanical/electrical engineering
- Structural engineering
- Air permitting and compliance