The expanded biological nutrient removal process at the Algonquin (Ill.) Wastewater Treatment Facility is as chemical-free as possible. Credit goes to the design of the plant and to the innovative efforts of the staff.

 

“We’re a biological operation,” says Andrew Warmus, utilities superintendent. “The only chemical we use is ferric chloride for phosphorus control, and we’ve been able to reduce the use of ferric to less than 10 percent of the original engineering estimates.”

 

That, plus UV disinfection instead of chlorine, has just about eliminated chemicals, reducing operating costs, producing less sludge, and assuring production of biosolids suitable for land application.

 

A fast grower

The Village of Algonquin is located along the Fox River, about 45 miles northwest of downtown Chicago. It’s an attractive suburb, and the population has increased rapidly to its present 30,500. By the mid-2000s, growth had outpaced the capacity of the previous 3 mgd (design) activated sludge treatment plant.

 

The facility, built in the 1970s, had been upgraded and expanded in phases since 1975. “The old plant simply couldn’t keep up,” says Warmus. “We were running at 110 percent of design. We needed more hydraulic and organic capacity.”

 

Fortunately, the village and its engineering consultant, Trotter and Associates of St. Charles, Ill., had prepared for future requirements for nitrogen and phosphorus removal in an earlier facilities plan. Contractors broke ground for the new facility in 2006. At $16 million, it was the largest public works project in village history, and it increased capacity to 5 mgd. The facility went into operation in February 2008.

 

Reducing nutrients

“It’s an outstanding design,” Warmus says. Treatment is centered around a five-stage Bardenpho process. Wastewater is collected in 134 miles of sanitary sewer lines and 10 lift stations, then passes through Envirex (Siemens) bar screens at the headworks. A force main carries the flow into four Envirex rectangular primary clarifiers. Settled solids are anaerobically digested.

 

Primary effluent and return activated sludge from the final clarifiers merge in the first stage of the Bardenpho process — an anaerobic basin. The flow then passes to the second-stage anoxic zone, an aerobic zone, another anoxic zone, and then to a final aerobic zone.

 

The aerobic zones facilitate nitrification, while denitrification occurs in the anoxic zones. The anaerobic zone is an addition to the conventional four-stage Bardenpho process and is included for biological phosphorus removal. A chemical precipitation system using ferric chloride is available for enhanced phosphorus removal as needed.

 

A pair of Envirex Tow-Bro circular clarifiers receive the treated effluent, and a TrojanUV3000 system disinfects the water before discharge to the Fox River. Alternatively, effluent can be recycled and reused by area contractors for dust control and irrigation (see sidebar). The new process can reduce total effluent nitrogen to less than 5.0 mg/l and phosphorus to less than 1.0 mg/l.

 

Pumps move waste activated sludge to a serpentine, three-basin aerobic digester. Both primary and secondary biosolids streams are conditioned with polymer and dewatered separately on Ashbrook belt filter presses. A private contractor applies dewatered cake to area farm fields.

 

The plant’s SCADA system, which includes Allen-Bradley (a division of Rockwell Automation) PLCs and Intellution software, provides monitoring and control at five locations within the plant as well as on staff laptops. It was developed by Tri-R Systems, which acted as electrician and system integrator in what Warmus calls a “good marriage.”

 

Six people manage and operate the plant from 7 a.m. to 3 p.m. on weekdays. An alarm system is available to alert operators during off hours. An on-call person responds to alarms after hours and spends a couple of hours on Saturday and Sunday to check plant operation.

 

The operations team includes Steve Fiepke, chief operator; Tom Hall and Randall Frake, operators; Rahat Quader, laboratory technician; Dalton Wall, maintenance; and Cathy White, environmental compliance coordinator.

 

Ferric be gone

“Understanding and improving the process has been a collaborative effort, drawing upon operating staff experience, plant data and observations, and a desire to produce the highest-quality effluent possible,” Warmus says. “Staff took an excellent design and improved upon it.”

 

For example, original estimates put ferric addition for enhanced phosphorus removal at 300 gpd, but the Algonquin staff reduced consumption to just 30 to 50 gpd.

 

White notes that the team approach has made a significant impact. “In our biological process, we’ve focused on allowing our phosphate accumulating organisms (PAOs) to do their job by creating a good environment for them and supplying them with enough food source (volatile fatty acids),” she says.

 

That results in an increased population of PAOs and more phosphorus accumulation, or uptake. In the anaerobic zone, the PAOs convert the carbon source to carbon compounds, which then fuel even more phosphorus uptake by the PAOs in the aerobic zone (luxury uptake).

 

“We’ve been pleasantly surprised,” White says. “Normally it might take five to six years to see this level of phosphorus removal, but we’re seeing it in only a couple of years. We’re making headway.”

White points out that filamentous growth has historically been an issue at Algonquin, and those organisms tend to compete with the PAOs for volatile fatty acids. To offset that, the plant staff controls the amount of time biological sludge stays in the system in an effort to prevent the long sludge ages that filamentous organisms prefer.

 

Further tweaks

The Algonquin crew has made other adjustments to reduce phosphorus further. “All our basins except Basin 1 contain mixers,” says Fiepke. “We’ve experimented in anaerobic Basin 1, running the mixers in an on-and-off mode. That enables us to achieve a negative ORP (oxidation reduction potential) in that basin, and improves phosphorus removal.”

 

In another tweak, operators observed a high return rate from Basin 3 to Basin 2. “We were getting some backwash into Basin 1, and the nitrates were interfering with phosphorus removal,” says Fiepke. “It was simply a design issue, and we’ve reduced the return rate.”

 

High flows can also affect phosphorus removal. “In some winters, we have a lot of snow melt, and that can increase the hydraulic flow through the plant,” explains Fiepke. “The PAOs need sufficient time to cycle, and high flows can reduce their ability to uptake phosphorus.”

 

The staff has countered by turning off the mixers in the anaerobic zone for a longer time so that the organisms don’t get washed out. Warmus adds that the village’s underground crew is making progress tightening up the sewer system to prevent inflow in the future.

 

Go, team

It’s a team approach to problem solving that makes a success out of a treatment plant that is quite different from the one that used to serve Algonquin. “We have a good crew here, with good ideas,” says Fiepke. “They’re dedicated and knowledgeable, and that’s the reason for our good performance.”

 

An example is a staff-driven solution to an odor issue. “Our aerobic sludge digesters are covered so that we can control temperatures during the winter months,” says Warmus. “The covers have vents to allow air to circulate, but odor issues were developing at those vents.” Fiepke and operators Hall and Frake came up with a solution.

 

“They took 55-gallon drums, cut the ends off, and placed them over the vents,” Warmus says. “Then they placed cedar woodchips and other granular odor control media in the drums.” The result: a homegrown biofilter that’s effective and didn’t cost very much.

 

It’s just another way in which the team at Algonquin is steadily improving the treatment process and delivering quality service to the community.