Resource Recovery and Energy Optimization

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biosolids being spread at METROGRO Farm

Biosolids

  • Beneficially reuse 85 dry tons of biosolids per day
  • Return nitrogen, phosphorus, and other minerals to land while sequestering carbon
  • Maintain Metro Water Recovery’s 52,000-acre farm
  • Distribute and land apply biosolids at 379 permitted private farms

Nutrients

  • Recovered struvite (crystalline phosphorus product) distributed to composter for generation of specialized high-P fertilizer
  • Investigating the recovery and reuse of sulfur for various purposes as part of the renewable natural gas project
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thermal energy graph

Thermal

  • Extract heat from wastewater during cold periods to reduce the treatment plant effluent temperature and offset natural gas heating demand
  • Sink heat from conditioned spaces during warm periods into the wastewater to offset electricity demand from HVAC cooling

Renewable Methane

Anaerobic digestion generates biogas comprised primarily of methane and carbon dioxide that may be recovered for beneficial use such as heat or power generation.

Renewable Natural Gas

  • At the RWHTF, a design is underway for a biogas conditioning system to produce renewable natural gas for pipeline injection. This natural gas will provide a renewable fuel source for transportation and consumer heating.
A diagram showing how gas from the digester is used as energy.

Electricity

  • Electricity is currently generated at both NTP and RWHTF through the combustion of renewable methane. This production offsets 40% of electricity purchases at the RWHTF. Heat is recovered during the process to support process needs and supply building heat for many large process buildings.
  • At the RWHTF, additional efforts are underway to increase the reliability of electricity purchased from the utility.

Capital Investments

PAR 1265 – Electrical Transmission-Level Service Substation (RWHTF)

2021-2026 Investment: $72.6M

Provide high-voltage, transmission-level electrical connection to the RWHTF to improve reliability, increase operational flexibility, and reduce annual operating expenses.

PAR 1395 – Cogeneration Equipment Replacement (RWHTF)

2021-2026 Investment: $50.7M

Replace the existing combined heat and power (CHP) system with a renewable natural gas (RNG) system capable of treating the biogas to a pipeline quality for injection into Xcel’s pipeline.

PAR 1401 – Alternative Energy Evaluation (RWHTF, NTP, Farm)

2023-2035 Investment: TBD

Develop solar and wind energy at the three large Metro sites, RWHTF, NTP, and METROGRO Farm, in areas were improvements are not anticipated for 20 years or where operations will not be impacted.

Innovations

Land application of biosolids leads to a reduction of 14,000 metric tons of CO2-eq each year.

Robert W. Hite Treatment Facility

Capital Investments (15 years)

Projects are based on the current anticipated regulatory requirements but are subject to change without notice. Projects are planned and are subject to change without notice including the cost estimates.

Heat Recovery Facilities

Investment: TBD

Provide heat recovery facilities to supplement heat demands in processes and conditioned spaces across the RWHTF, offsetting natural gas consumption, reducing emissions, and reducing cooling system requirements.

Upcoming Innovations

Incorporation of heat recovery systems for use in process building heating to reduce operational and capital costs associated with cooling towers.

Treatment Process Map Learn more about biosolids Learn more about the collection system Learn more about the influent Learn more about the sources