When the City of Chandler, Arizona's Ocotillo Water Reclamation Facility (WRF) was named the 2010 Wastewater Treatment Plant of the Year by the Arizona Water Association, it wasn't the first time the facility had been recognized for its excellent operation.
For years, the 10-mgd plant in the Phoenix suburb has been considered an innovator, as it recycles all its treated water. The water is placed in storage lakes, recharged to the aquifer, sent to an industrial user or sent to an adjacent Indian community for agricultural use. Intel, the international technology company, which operates three nearby chip fabrication plants, also uses the reclaimed water as a source of cooling tower water. Over the past decade, the company has worked with the City of Chandler to implement a progressive water management system that reduces the use of water by millions of gallons each day. During that time, Intel has used more than 4.5 billion gallons of treated wastewater from the Ocotillo WRF instead of tapping into potable water supplies.
Since 1985, the operations and maintenance of the Ocotillo plant has been managed by Severn Trent Services through a public-private partnership with the City. One of the services Severn Trent has provided for the City — and for increasing numbers of other public-private partners — is a Site Energy Management Plan (SEMP) audit to evaluate and create action plans to improve plant energy efficiency. Long viewed as a financial burden, power consumption at water and wastewater treatment plants is now considered a major environmental burden as well. Energy costs are the second largest expense for treatment facilities — 28 percent of total operating expenses for wastewater facilities. Reducing power consumption, resulting in reduced operating costs and maximized process efficiencies, is one way utilities are generating savings and minimizing their carbon footprint. At the Ocotillo plant, energy usage was reduced by eight percent in the first 12 months after implementation of the SEMP recommendations began.
Many of the achievements cited by the Arizona Water Association in honoring the Ocotillo WRF were related to ongoing energy efficiencies, carbon footprint reduction and cost savings made possible by the SEMP audit. "We have conducted our energy efficiency program in conjunction with the PowerWise Custom Business Solutions rebate program run by Salt River Project (SRP), metropolitan Phoenix's energy provider," said Greg Stack, project manager for Severn Trent Services. "The program provides businesses with rebates for reduced energy usage and for the purchase of energy efficient equipment such as efficient motors, variable frequency drives, LED lights and lighting with high efficiency ballasts. So, on top of the savings from reduced energy, Severn Trent Services is eligible for significant rebates from SRP as well."
Some of the Ocotillo WRF's biggest savings have come in the replacement of old equipment with more energy efficient models. For example, any motor throughout the facility whose useful life has expired is replaced with premium efficiency motors. When aging blowers needed to be replaced, Severn Trent turned to blowers that are radically different in technology due to efficient bearings and motors — and are 30 to 35 percent more efficient than the old blowers. The bearings are air bearings which ride on a cushion of air, reducing friction. The blower motors are made of rare-earth materials, whose magnetic characteristics reduce energy usage and wear. Switching from the 300 HP conventional centrifugal blowers to 300 HP high-speed turbo blowers helped reduce energy usage by 736,698 kWh.
The one-time SRP rebate in 2010 amounted to just over $81,000.
"We also participate in an SRP program designed to curtail power use during times of peak demand," Stack noted. "When asked by SRP — and when operationally possible — we'll cut back our energy usage for a few hours. This helps SRP avoid having to purchase more expensive power, and Severn Trent Services benefits with an additional rebate."
Ocotillo personnel also optimize the performance of the plant with an aeration basin air flow control system, which ensures they are using the exact amount of oxygen needed flowing to the aeration basins — no more.
"We seek out savings in other ways, too," Stack added. "We have optimized our control system to reduce the use of sodium hypochlorite, which also reduces energy. And by decreasing the amount of water in our solids treatment process, we have reduced the amount of sludge that must be sent to landfills, saving diesel fuel."
The 2010 Wastewater Treatment Plant of the Year award wasn't the only recognition Severn Trent Services received from the Arizona Water Association this year. Four of the City's wastewater projects received safety awards and two employees were honored: John Bannen, western region health and safety advisor, received the Water Environment Federation Fuller Award for training program leadership; and Fred Kriess, senior area manager, received honorary life membership in the American Water Works Association for 30 years of membership in, and support of, the association.
Finally, the employees capped off a banner year by celebrating, on April 28, five consecutive years without a lost-time injury.
The Ocotillo WRF has become so well known for its efficiency and innovations that personnel have made accommodations for the occasional visitor from other wastewater utility operators. "The doors of our new turbo blowers are made of Plexiglas so other utility representatives can get a good look at how it operates," said Stack.
For more information, e-mail info@severntrentservices.com.
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