Fine-Tuning the System

Use of off-peak electricity and gravity-powered water delivery gives Truckee Meadows Water Authority a better way to manage energy and control costs.

In the high desert of Reno, Nev., Truckee Meadows Water Authority strives to produce the highest-quality drinking water as cost-effectively as possible. For the past three years, the utility has taken full advantage of off-peak electric rates and has eliminated the use of pumps to deliver water to one treatment plant. Such initiatives save more than $1.7 million in electricity per year.

Truckee Meadows serves a population of 350,000 in Nevada’s Washoe County. About 90 percent of the area’s water comes from the Truckee River, which originates at Lake Tahoe. For summertime demands, backup for the surface water treatment plants, and during drought conditions, the utility operates and maintains 30 wells.

Surface water is treated at the Chalk Bluff and Glendale plants, where raw water undergoes pH adjustment, coagulation, multiple flocculation stages, sedimentation, filtration, disinfection and final pH adjustment. Maintenance and distribution crews maintain 91 booster pump stations, 140 pressure-regulating stations, 42 storage tanks and 1,300 miles of pipeline.

Groundwater is treated for perchloroethylene (PCE) at three facilities; water from some wells is routed to the Glendale plant for arsenic removal. The entire water system can process 190 mgd, but the average is 70 mgd (30 mgd in winter, and a maximum of 149 mgd in summer). The utility’s annual treatment operations budget is $8.5 million.

Changing philosophy

In 2009, Truckee Meadows discovered that energy was its second-largest cost after labor. That led to a cost-reduction program involving optimization of off-peak power for plant operations and distribution and reductions in demand charges from NV Energy, the local utility.

“For instance, if a pump station pulls 100 kW during on-peak demand, we may be charged $5 per kW,” says Ryan Dixon, supervisor of water operations. “But if we can cut that down to 50 kW, we get a reduction of half for the demand portion of the bill. We can really save money by using our facilities during off-peak hours.”

A team headed by Keith Ristinen, senior engineer, reviewed ways to operate on off-peak times whenever possible. Using hydraulic models of the distribution system and seasonal demand data, they identified pumping scenarios for meeting customer demand at the lowest cost. Optimizing time-of-use rates for the distribution system has saved $265,000 a year.

“We would play the ‘what if’ game,” Ristinen says. “What if we run one pump all day? Is that cheaper than running two pumps and filling a tank during off-peak hours? Or what if we used two different pump stations? We have various ways of moving water through our system.”

They conducted a similar analysis for the Chalk Bluff treatment plant. Operators can control four main areas to operate off peak: filling reservoirs and tanks, backwashing filters, pumping finished water, and pumping well water. Dixon and his team set energy targets each day. “The targets allowed us to maximize energy efficiency,” he says. “By avoiding large peaks in usage, we lowered our facility charges and demand charges. That’s how we were able to reduce costs.”

These measures involved no capital investment, but required about 80 hours of engineering labor to set up system controls.

Becoming believers

When initial analysis showed the potential savings from time-of-use rates at Chalk Bluff, Dixon needed the 16 operators to be on board. “We sat down and told them what we wanted to do,” he says. “Initially there was skepticism about why we were doing it and what we would accomplish, but once we posted the energy bills for operators to see, they recognized that their efforts were paying off. They appreciate having this level of control.”

In 2011, Chalk Bluff had its lowest electric bill since it went online in 1994, even though production had steadily increased. Use of off-peak rates has saved $225,000 annually and earned the facility the 2012 Outstanding Energy Management Award from the local section of AWWA.

The operators engage in friendly competition to stay within the energy targets. “Our operators are very good at looking forward and being creative,” Ristinen says. “They may fill up a tank during a shift and leave the filter backwashes to mid-peak so they can squeeze by until the next day. These guys are fantastic at predicting what’s going to happen and setting up the next crew to minimize the electrical consumption. It’s something that we measure and track.”

Gravity as advantage

The utility also reduced energy costs by making better use of gravity. In 2004, the 8-mile Highland Canal that supplies river water to Chalk Bluff was renovated to reduce vulnerability to earthquakes and prevent flooding in surrounding neighborhoods. Those improvements also increased capability to supply the plant using gravity. Over the past eight years, updates to extend the canal walls and increase volume have raised capacity from 50 mgd to 75 mgd. More construction is underway to increase capacity to 90 mgd by mid-2013.

The $2.5 million Highland Canal improvement project, funded by a State Revolving Fund Loan, also earned a one-time $82,500 rebate from NV Energy. Using gravity instead of a 4,000 hp pump station to feed raw water to the plant has saved $1.2 million a year.

With help from some smart meters installed by NV Energy at 200 sites in the system, Truckee Meadows plans to investigate more ways to improve energy efficiency at its plants, particularly by updating old lighting, pumps, and heating and cooling systems. “The smart meters will better track our energy use at each facility,” Dixon says. “We look forward to seeing where our energy is going and how we might find further savings. It’s going to be a balance between capital investment and energy efficiency. We expect the smart meters to help us focus our priorities.


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