March 2009, Vol. 21, No.3

Plant Profile

City of Burley WastewaterTreatment Plant

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Location: Burley, Idaho
Startup date: June 6, 2007
Service population: 10,000
Number of employees: 5
Design flow: 2.5 mgd (9500 m3/d)
Average daily flow: 1.4 mgd (5300 m3/d)
Peak flow: 10.5 mgd (39,700 m3/d)
Annual operating cost: $540,000

In 2006, the City of Burley, Idaho, partnered with Veolia Water North America (Chicago) to operate the city’s new wastewater treatment plant. With a planned startup of June 2007, the city moved several years earlier to retain a qualified plant operator to ensure that the facility would comply with Idaho’s stringent environmental regulations from Day 1 while protecting the city’s new asset in the long term. The partnership, to date, has been recognized regionally and nationally for its high level of operational performance and environmental quality standards.

The Burley Wastewater Treatment Plant was designed to meet federal and state environmental standards today and for the foreseeable future. For example, the effluent produced by the plant was planned to meet Idaho’s Class A reuse-water requirements. The stringent Class A reuse water is equivalent to California’s Title 22 water, which requires high water quality treatment and disinfection to allow the reuse of water for various nonpotable uses.

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The plant is also designed to produce high-quality fertilizer that meets U.S. Environment Protection Agency Class A biosolids requirements. Processed in a thermal dryer, the biosolids are an excellent and free fertilizer that greatly reduces landfill waste.

The final design for the facility was completed in 2004. The project was bid in November 2004; construction began in March 2005 and was completed in September 2007. The plant’s primary sources of influent are domestic, but Burley is expanding with new business. The plant currently treats the cooling-tower discharge and boiler blowdown from a local ethanol refinery, which produces ethanol from corn. This facility is regulated by the pretreatment program and has been permitted to discharge. There are many new industries looking to locate in Burley, and these also will be permitted to discharge.

Burley Operations
Wastewater entering this new plant is screened through a 6-mm bandscreen system, which includes a grinder–compactor. Then, a cyclone degritting system removes smaller particles. The main process is a biological nutrient removal system that uses an oxidation ditch with diffused aeration and multistage centrifugal blowers. In this system, mixing and aeration are controlled separately so energy usage can be controlled. The city constructed extra tanks and included necessary equipment so capacity can be increased from its initial level of 2.5 mgd (9500 m3/d) to 5 mgd (18,900 m3/d) with little modification. Following secondary clarification, tertiary filters further reduce total suspended solids and aid phosphorus removal. The filtration step is a requirement of the reuse regulations. Typical effluent concentrations of total suspended solids are less than 5 mg/L, and biochemical oxygen demand concentrations are typically less than 8 mg/L. Finally, an ultraviolet disinfection system kills any remaining pathogens. The final effluent averages levels of 1 colony-forming unit per 100 mL for fecal coliform and Escherichia coli.

Waste activated sludge (WAS) from the secondary clarifiers is thickened to 4% from about 1% using the gravity zone on one of the plant’s two belt filter press. The thickened solids are added to one of the plant’s two aerobic digesters. Thickened WAS is taken from the digester and dewatered to 16% to 20% solids using the belt filter press and then sent to the solids dryer. This system produces Class A biosolids. So far, the city has used this product as a fertilizer on its golf course and provided it to local residents for their use.

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Startup Challenge
During the facility startup, the automation system for activated sludge return and blower control was not complete and had to be operated by hand. During this time, the plant experienced an increase in effluent phosphorus numbers; concentrations increased to about 6 mg/L. Troubleshooting revealed that due to the low flow overnight, the high return activated sludge return rate, and the high dissolved-oxygen setting in the oxidation ditches, the dissolved-oxygen levels were too high in the anaerobic selector portion of the ditches.

By reducing the return activated sludge return rate at the end of the day and working with the blower-control vendor to program the blowers to shut down between 2 a.m. and 7 a.m., operators were able to decrease the effluent phosphorus concentration from greater than 6 mg/L to less than 1 mg/L within only a few days. The plant now operates with the blowers off during the early morning, decreasing energy consumption and achieving optimal nutrient reduction.

Safety Record
All employees are involved with facility safety. Veolia Water provides safety training to ensure plant security and possible solutions to issues that arise. The Burley plant as of Jan. 5, 2009 had gone 1009 days without a loss-time accident. Daily 5-minute “tailgate safety talks” are held and attended by all employees, along with monthly in-depth training. New employees are given 10 hours of U.S. Occupational Health and Safety Administration training by the company’s environmental, health, and safety team.

Veolia Water also has implemented a mental safety assessment program. This program provides training so that individuals can assess each job before it begins in order to complete the job safely. The program encourages staff to think through a project before beginning it to ensure that all safety hazards are identified, addressed, and resolved.

©2009 Water Environment Federation. All rights reserved.