Resource Recovery and Energy Optimization

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

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.

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.

A diagram showing how gas from the digester is used as energy.

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