AECOM and Veolia Help Advance Wastewater Treatment Microgrid in Southern California

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The city of Rialto, California, is moving ahead with plans to build a microgrid at a wastewater treatment plant with support from Veolia and AECOM.


Rialto wastewater treatment facility. Photo courtesy of Veolia North America.

AECOM was selected to design the $8.2 million microgrid, which is expected to include a 360-kW reciprocating engine that would run on biogas, a 1.6-MW photovoltaic system and a 2.5-MWh lithium ion battery that could run for four hours before needing to be recharged.

The generating units would provide all the facility’s electric needs, and the microgrid will allow the plant to run when there are power outages.

“As California and the rest of the country contend with a growing number of natural disasters linked to climate change — including widespread power outages and brownouts caused by heat waves and wildfires — the resilience offered by a microgrid power source is more important than ever,” Rialto Mayor Deborah Robertson said March 17.

The wastewater treatment plant is run through a partnership between Rialto Water Services and Veolia North America.

Microgrids increasingly used in wastewater treatment

Microgrids are increasingly being used at wastewater treatment plants, partly to save money and partly to prevent raw sewage from entering waterways during power outages. 

Four years ago, Public Service Electric and Gas started operating a wastewater treatment microgrid in New Jersey, and last year the McKinleyville Community Services District in northern California selected Ameresco to build a $2 million microgrid at a wastewater treatment plant.

Microgrid to cut utility bills

Rialto, a city of about 100,000 east of Los Angeles, expects the project will cut the treatment plant’s utility bills. The facility’s annual electric bills are about $772,000 and its natural gas charges are about $91,000, according to a Feb. 23 presentation to the city council.

Instead of flaring biogas at the plant, the biogas will be used to run a cogeneration facility that will also provide heat for the plant’s anaerobic digesters. 

The planned system will avoid the use of natural gas in two ways. First, natural gas must be mixed with the biogas to burn it off, according to the city. Second, the natural gas currently used to heat the anaerobic digesters will no longer be necessary.

The project is expected to reduce carbon dioxide emissions from the treatment plant by about 600 million metric tons a year.

Rialto expects it will be able to sell excess energy from the project into the power grid.

Anticipating $1.9 million in incentives for the project, Rialto forecasts $460,000 in annual cost savings for the city, according to a feasibility study prepared by SourceOne, a Veolia Energy unit.

Construction likely in 2022

After the design process is finished, construction on the project is expected to start in early 2022 and be completed about a year later.

AECOM beat out Arup and Jacobs Engineering for the contract to design the microgrid. Under the contract, AECOM could go on to build the microgrid.

Interested in microgrids? Join us for Microgrid 2021: The World Awakens to Microgrids, a virtual conference hosted by Microgrid Knowledge. Participation is free for those who register in advance.

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  1. In Palm Springs California, the waste water treatment plant there became privatized in 1999 around the time of the ENRON grid debacle. A small pilot installation of solar PV was tried and I believe in 2015 a much larger system was installed to help run the plant. Following this lead, the local UPS distribution warehouse had the roof of the complex loaded with solar PV panels to run the operations. Several local Indian Casinos have installed solar PV and energy storage and can actually “island” from the grid for a few hours if needed. To some it seems ‘trivial’ until a summer storm takes out power when it’s over 100 degrees F outside and this may last several hours until power is restored.

    “Instead of flaring biogas at the plant, the biogas will be used to run a cogeneration facility that will also provide heat for the plant’s anaerobic digesters. ”

    This practice is becoming more common, the switch from aerobic (open air) to anaerobic digesters (closed system). The off gassing can be scrubbed, stored and used in turbines or standard compression ignition generators to help offset utility “demand charges” that can add up to 50% of the cost of a monthly electric bill. When one has electric bills of $100,000 or more per month, a 10% to 50% ‘price’ savings on electricity is an aggregate savings of millions of dollars over years of use. A careful analysis of (how the local electric utility) administers and when the utility administers TOU or “demand charges” could be offset with solar PV and energy storage at every domestic water or sanitation site in a particular service area. Avoiding just 3 or 4 hours of demand charges or TOU rates can save money on overhead costs for years to come.