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Green Projects

The City of Riverside is committed to making our town a greener place to live by supporting renewable energy, responsible purchasing and design, and sustainable practices. The Riverside Water Quality Control Plant (RWQCP) has invested in and established several green projects designed to use byproducts of the sewage treatment process to produce energy.


cogeneration plantWastewater treatment at the RWQCP involves anaerobic digestion where, in the absence of oxygen, bacteria digest residual solids and create methane gas as a byproduct.

This gas is mixed with a small percentage of natural gas to fuel three Caterpillar internal-combustion reciprocating engines that run generators, each of which is rated to produce 1.1 megawatts.

Heat produced by the operation of the engines is used to heat the digesters for optimum performance in the generation of gas. The generated electricity is used in various processes throughout the treatment plant.

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The Riverside Water Quality Control Plant (RWQCP) generates about 100 Wet Tons per Day (WTPD) of Class B digester sludge (“biosolids”).

Our biosolids are used in two ways:

  1. biosolid land applicationBiosolids are safely applied to farmland in Arizona where they act as a beneficial amendment to farmland and an environmentally-friendly alternative to petroleum-based and chemical fertilizers.
  2. Biosolids are sent to Nursery Products, LLC, a composting facility in Helendale, CA where biosolids are combined with green waste to generate Class A compost. The compost is then used by farmers to provide essential nutrients to their crops without chemical fertilizers, while reducing water usage and improving soil quality.

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Grease to Gas

On April 27, 2005, the City began the Grease to Gas to Power project. Local grease haulers who pick up Fats, Oils, and Grease (FOG) were able to take FOG to the RWQCP for processing and injection into anaerobic digesters. By adding this grease wastewater to the anaerobic digestion process the RWQCP was able to increase gas production and methane gas concentration. The project was a huge success and has been the recipient of many awards.

The plant expansion includes expanding and improving this project through the construction of the new FOG Receiving Station. The new station can process up to 60,000 gallons of grease wastewater each day. This new receiving station will enhance biogas production in anaerobic digesters. Biogas is then converted to electricity using a Cogeneration System.

By offering local grease haulers a safe way to dispose of restaurant grease, this component of the plant expansion will have a significant positive impact on the environment and provide a beneficial use for wasted grease from local restaurants and food processing facilities.


The City’s Public Works Sewer Division Grease to Gas to Power project has achieved the following:

  • 2008 Three 20th Annual Clean Air Awards from the South Coast Air Quality Management District.
  • 2007 League of California Cities, Helen Putman Award for Planning and Environmental Quality.
  • 2007 California Municipal Utilities Association, Community Service/Resource Efficiency Award, Public Benefit Funds, Large Utility.
  • 2007 American Public Power Association, Energy Innovation Award.

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Quick Links
Sewer Rates & Fees
2019 Sewer Master Plan
Other Wastewater Resources
General Information
Riverside Water Quality Control Plant (RWQCP)
5950 Acorn Street
Riverside, CA 92504

Phone: (951) 826-5311
The 311 Call Center is open during normal business hours to assist you.

After Hours Phone: (951) 351-6140
In case of an emergency or sanitary sewer overflow, please contact the RWQCP after hours number for immediate assistance.

Admin Hours:
Hours: M-F 7:30 am-4:30 pm  
Closed on Weekends and Major Holidays
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