Green Through and Through

A LEED-certified treatment plant in Champaign County has features that improve operations and safety while saving energy and limiting the environmental footprint.
Green Through and Through
Plant operator Darrel Vanover tests for free chlorine and total chlorine.n

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Operators had plenty of input to the design of the new Bradley Avenue Water Treatment Plant in Champaign County, Ill. Their input helped the plant earn green building certification under the U.S. Green Building  Council’s Leadership in Energy and Environmental Design (LEED) program. Now, those design elements help the plant operate efficiently and safely.

Illinois American Water operates the 15 mgd plant, built on a greenfield site and commissioned in December 2008. The plant received LEED certification for its overall design, which includes a variety of energy-saving, recycling and sustainability features. “To build this plant, we developed a project team at the very start that included operations people,” says Brent O’Neill, engineering manager. “Many design items were specific suggestions from the operations staff.”

Walter Voegel, operation supervisor with Illinois American Water, was a member of the project team and was supervisor at the plant from startup through 2012. His experience counted heavily in the design, especially in automation and safety. “Since the operators of the new plant had experience with the other plants in the Champaign area, it was important for the new design to use similar processes,” he says.

Operator suggestions involved chemical handling, equipment layout, the SCADA system and the location of the operator control room and laboratory in the overall site plan.

Dual treatment trains

The Bradley Avenue plant, in a rural area about seven miles west of downtown Champaign, treats groundwater with a lime softening process. With two other plants in the city, it feeds finished water to a system that serves 150,000 people in the Champaign-Urbana metro area.

Six new wells (Layne) averaging 340 feet deep and with capacities of 2.5 mgd each draw raw water from Mahomet Aquifer. The flow is pumped to a dual-train lime system, each train with 10 mgd capacity, in step with a design that allows the plant to be expanded to 20 mgd in the future.

The lime process settles out iron and manganese and softens the water. Each train consists of a primary and secondary clarifier (Walker Process). In the primary clarifiers, the flocculated water stratifies into three levels: supernatant on top, the sludge blanket in the middle and the slurry pool on the bottom. Radial launders convey the clarified water to the outlets, and it passes to the secondary clarifiers for further settling. Calcium and magnesium precipitate out of the sludge blanket to the slurry pool.

Lime slurry is prepared in an automated, temperature-controlled TEKKEM batch slaking system (RDP Technologies). The fully enclosed system is gravity-fed; pumps are required only to move the slurry to the clarifiers. Water then passes to a re-carbonation tank, which bubbles carbon dioxide through to lower pH. The flow then passes through dual-media sand and anthracite gravity-flow filters with underdrains (The Roberts Filter Group).

Intelligent sizing

A system from Siemens Water Technologies generates sodium hypochlorite on site. Added in the clearwell, it works with naturally occurring ammonia in the water to form chloramines. Three 7.5 mgd high-service pumps (Afton Pumps) deliver treated water to the Champaign system.

Finished water storage facilities are sized to provide adequate detention time for disinfection, to provide water for filter wash and other plant uses, and to provide equalization between plant production and distributive pumping rates. Vertical turbine pumps in the clearwell transport finished water to the distribution system.

When lime solids accumulate beyond the optimum solids concentration in the clarifiers, they are automatically blown down to holding lagoons and stored for up to three years. A local agricultural company harvests the solids for application to farm fields. “It’s a process we brought over from the other plants,” says Steve Wegman, senior engineer with Illinois American Water. “It’s a cost-effective way to manage solids, and it benefits the local farmers.”

The plant is staffed around the clock with an operator on each of three shifts. A SCADA system monitors and controls all treatment processes and offers the potential for remote operations. Illinois American Water maintains a five-person maintenance crew that services all three Champaign plants. Supervisor David Farrar oversees the entire Champaign operation. Operators rotate among the three plants.

Designed for operators

The Bradley Avenue plant balance sheet benefits from a number of LEED features, but so do the operators, because process equipment runs reliably, lasts long and needs limited maintenance.

“LEED features can improve operations, or they can make things more difficult,” says O’Neill. “LEED simply means the feature is approved as environmentally friendly. The technologies employed as part of the LEED items were selected to reduce impact on the operators. In most cases, the items were being used at other locations, reducing the need for special training.”

All pump motors are equipped with variable-frequency drives (Danfoss), making the system easier to operate and saving on electricity and pump wear. The air scour component of the filter backwash system (United Blower) saves water and extends filter media life while effectively backwashing the filter. Wegman notes that the design of the recarbonation tank improves the distribution of carbon dioxide and generates less carbonation, also adding to media life.

Other LEED features assure safety at the plant. With operator input, the chemical loading bay was designed so that delivery trucks pull into an area slightly lower than the rest of the driveway. That way, any spills can be contained. Storage tanks also can be isolated. “Ordinarily, any rainwater collecting in this area flows by gravity to our stormwater pond, but during chemical delivery, the valve is turned off so that in the event of a leak, the chemicals can be contained on site,” Voegel says. “Each chemical is stored in its own separate room, so there is no possibility of cross-contamination. Should there be a rupture, it would be contained.”

Voegel credits the automation system for enhancing safety: “We have sensor monitoring of all the individual rooms, tied back to the SCADA system in the main control room. That gives an operator a warning in case dangerous conditions should exist in a specific area. That’s important in a one-man operation. The safety showers are tied to the alarm system, as well, so that the supervisor can be instantly made aware of any situation.”

Realistic monitoring

Based on their experience at other facilities, operators helped develop the SCADA controls to ensure that the items monitored actually applied to facility operation and efficiency. “It’s a pretty autonomous system, with information and flow pacing based on demands and pressures leaving the facility,” says Wegman. Operators also recommended the central location of the operator control room and the laboratory.

Wegman notes that “dirty” chemicals like lime and ferric chloride are separated from the main building, making it easier to keep the administration and laboratory areas clean, saving on cleaning costs and extending the life of electronic components.

Voegel also notes that lime slaking is cleaner than older methods of making lime slurry. The system adds precise amounts of lime and water, and the chemical reaction takes place under optimum conditions in about 20 minutes. The batch temperature is closely monitored until the maximum temperature has been achieved, and only then is the batch discharged. The clarifiers use what is needed, then return any excess to a slurry holding tank. The design of the lime receiving system also allows for easier replacement of pipe sweeps.

Green attributes

Other LEED features that improve the operational and cost efficiency of the Bradley Avenue plant include:

  • Daylighting in the filter gallery and filter pipe gallery, reducing artificial lighting.
  • Dark-sky outdoor lighting fixtures that limit light pollution in the neighborhood.
  • Recycling of all process water, saving water and reducing the need for infrastructure to take and treat storm flows offsite.
  • Geothermal heating and cooling of the administrative portion of the plant.
  • Permeable paving in the driveway that allows stormwater to percolate to groundwater, reducing the size of the stormwater collection system.
  • Use of more than 46 percent local materials, lowering transportation energy costs.
  • Extensive recycling so that 75 percent of construction waste was kept out of landfills.

Good stewards

The LEED features have had an even wider impact: While the Bradley Avenue plant lies in a rural area, there are neighbors within a quarter-mile of the site. “We had pretty extensive public meetings with the city and with the local property owners,” says O’Neill. “Originally, there was an organized effort to prevent the plant from being built, but we addressed the concerns and talked about the processes, the designs, the wells.”

The neighbors were concerned about noise and pollution, and that was a factor in adopting dark-sky lighting rather than traditional floodlights. “We also located the plant back off the road and lowered the profile of the lime silos and the building itself,” says O’Neill.

The facility designers also committed to minimizing waste. All water used in treatment, including the filter backwash, is decanted and sent back to the head of the plant. Stormwater is pumped to a lagoon and allowed to percolate into the ground.

In the end, says O’Neill, “Our people take pride in knowing they are delivering high-quality water in an environmentally friendly way.”



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