Power Trip

Fairfield takes control of unnecessary electricity usage and high energy bills by operating its water treatment plant more efficiently and adding renewable sources.
Power Trip
Aerial view of the treatment plant and solar array.

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In 2000 and 2001, an electricity crisis in California caused rolling blackouts and brownouts affecting hundreds of thousands of customers. The state Public Utilities Commission had already provided for options to implement time-of-use conservation measures to help protect the state’s power grid.

Those restrictions caused the Water Department in Fairfield, Calif., to begin an aggressive power reduction initiative that has cut energy bills by 20 percent, reduced reliance on the grid and enhanced operating efficiency.

Even before the power crisis, in 1999, the department installed a power monitoring system at the North Bay Regional Water Treatment Plant (jointly owned with neighboring Vacaville) to help identify where to reduce power use. The 40 mgd capacity plant uses conventional treatment and granular activated carbon (GAC) filtration.

“This plant is not meant to start up and shut down, but the power company wanted us to shut down because they couldn’t keep power on the grid,” says Gil Hernandez, water treatment manager. “We did energy studies to figure out where to shave power and stay within the time-of-use constraints.” Data analysis revealed a new way of thinking that operators still observe.  During peak energy times, the plant refrains from running some pumps and holds off on filter backwashes.

“Operators had to get into the mindset of performing filter backwashes during off-peak times,” Hernandez says. “They had to plan ahead to backwash filters and pump the return wash water to backwash another filter. They challenged themselves to figure out ways to deal with the situation, working with what they had. They did a great job stepping up.”

Reducing consumption

Fairfield found other energy efficient solutions in the study data. First, the department installed variable-frequency drives (VFDs) on pumps in the contact basin, on sump pumps for flow drains and on motors on the ozone basin blowers. To help regulate flows in the wash water recovery system, a VFD was installed on a 40 hp recycling pump that ran constantly. Now, the pump runs 30 percent less while maintaining optimum flow.

By replacing an aging air preparation system with a liquid oxygen system to supply the ozone generators in 2009, Fairfield has saved energy and increased its ozone concentration. The air preparation system required refrigerant driers, desiccant dryers, liquid ring compressors and heaters to super-dry the air, all of which required substantial electricity. “The new liquid oxygen system uses less electricity and generates twice the concentration of ozone [6 percent versus 3 percent] to help better meet increasingly stringent regulatory requirements for total organic carbon removal,” says Mike Monroe, senior instrumentation technician.

In 2010, an ozone dose study revealed that by increasing the ozone gas concentration delivered to the pretreatment basin, Fairfield could shut down its post-treatment ozone injection point. Instead of running three 100 kW ozone generators at full output, the plant now needs, on average, only a single generator operating at 50 kW. The VFDs, the switch to liquid oxygen and the ozone dosage reduction have meant 20 percent energy savings worth about $100,000 a year. Fairfield’s continuing investments in energy savings include:

  • An energy management system for optimizing HVAC performance.
  • Interior lighting upgrades to LED fixtures along with occupancy sensors.
  • A downsized boiler for the heating system.
  • A small water heater for domestic use instead of using the master boiler.
  • A switch to ambient air instead of air conditioning for cooling the ozone generator cabinets.
  • Sun screens on doors and windows to reduce heat buildup.

Getting off the grid

To further reduce reliance on grid power and cut energy costs Fairfield, in 2007, began a long road to find a renewable energy solution. At the time, wind turbines seemed the best option because of consistently strong winds in the area. However, the Department of Defense informed the city that the turbines would interfere with the radar systems at nearby Travis Air Force Base.

Next, the team looked at solar power. Subsidies from the California Energy commission would support a solar array up to 1 MW that would cover 8 acres. However, the area around the plant was a potential habitat for the California tiger salamander, an endangered species, and mitigation would have been a cost-prohibitive proposition. The solar power plan was put on hold until 2012, when the city negotiated with area land developers to pay the mitigation costs.

A 1 MW ground-mounted solar array with 4,312 sun-tracking panels went online in August 2013. It fulfills 18 percent to 22 percent of the plant’s electrical demand. Fairfield entered a 20-year power purchase agreement with solar panel maker SolarWorld. The company owns and operates the solar array and charges a 20-year fixed price on the power generated.

Over the life of the project, the city expects to save $1.5 million to $3 million by purchasing power at the agreed rate of 11.5 cents per kWh instead of buying higher-priced grid power. “The idea has been to reduce our carbon footprint and lower our costs related to energy consumption,” Hernandez says. “We are able to do those things with this solar project. We’ve reduced our energy consumption from the grid, and it will save our ratepayers money in the future. Everybody’s a winner.”


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