Native American tribes strive to make decisions with thought about their effects seven generations into the future.

Wisconsin’s Ho-Chunk Nation couldn’t look that far ahead in planning a wastewater treatment plant upgrade. Still, the nation, under President John Greendeer, designed the plant to handle 30 years of expected growth, which includes an expansion of its casino at Black River Falls, a single- and multifamily subdivision with some 200 lots, a community center and possibly a school and a recreational vehicle park.

Today, the Wazee Area Wastewater Treatment Plant, serving about 500 residents of the Ho-Chunk community and 1,000 inmates and staff at the Jackson Correctional Institution, has a design capacity of 0.5 mgd and an average flow of 0.2 mgd.

Operated by Veolia North America, it has technology many smaller clean-water plant teams would envy, including an automated screening system in the headworks, automated dissolved oxygen control in the oxidation ditches, biological phosphorus removal, UV disinfection, a full SCADA system and a wastewater information management system for process control.

“The Ho-Chunk looked at their plans for the community and saw that they didn’t have the wastewater capacity they needed,” says Tim Wiesner, plant manager. “They made the wise decision to address that early, before we had any issues.”

Growth and progress

Wiesner, a Grade 4 wastewater operator who holds a bachelor’s degree in water resources from the University of Wisconsin-Stevens Point, runs the facility with Duane Johnson, a Grade 1 operator who has a two-year associate degree as an electrical service technician.

The current facility (0.265 mgd capacity) was constructed in 1996. Wiesner came to the Wazee plant in 1997 to lead the Veolia operation there. Before the plant was built, Ho-Chunk community residents used septic systems. Davy Engineering of La Crosse designed the plant, collections system and pump stations; Staab Construction of Marshfield built the plant.

The core process was an oxidation ditch, and the expansion, commissioned in mid-2014, essentially doubled the original capacity with a second slightly larger treatment train. As part of the $10.4 million project, the old system received upgraded motors and aerators. MSA Professional Services of Baraboo designed the expansion, and Staab Construction built it.

The plant consistently meets its BOD/TSS permit limits as well as a 1.0 mg/L phosphorus limit. “I’m pretty proud of the effluent,” says Wiesner. “We haven’t had a permit violation in years, and I definitely don’t want to have any from here on.”

Planned with care

Wiesner and the engineers chose technologies carefully. “We went around to other plants and looked at equipment, and that was fantastic,” he says. “We got to observe it in action and see what we liked and what we didn’t like so much. MSA brought good ideas. They designed the plant based on what we needed.”

The process begins with a pre-aeration tank. Wastewater from the prison, 6 miles away, arrives by way of a force main in which it can go septic and release hydrogen sulfide gas. “We didn’t want that gas in our new headworks building,” says Wiesner. “In the pre-aeration tank we can drive that sulfur into a form that’s not gaseous.”

Two Sutorbilt rotary lobe blowers (Gardner Denver) supply the air by way of Tideflex diffusers (Red Valve). The blowers also feed air to the aerobic digester and an aerated waste activated sludge holding tank.

From the pre-aeration tank, wastewater passes through a stair screen (Vulcan Industries) with an automated rake. Screenings are washed, compacted and dropped into a bagger for transport to landfill.

Automated aeration

Secondary treatment, a modified Bardenpho process, begins with a three-basin selector tank with anaerobic and anoxic zones where denitrification occurs and biological phosphorus removal begins. “The water runs through the first basin just to get the DO down,” says Wiesner. “Basin 2 and 3 are mixed with an internal recycle.

“The raw wastewater goes into Basin 2 and the return activated sludge goes into Basin 3. We are bringing the nitrate down in Basin 3, then mixing that return, which is now nitrate-free, into Basin 2 and getting phosphorus release in Basin 2 and Basin 3.”

The flow then passes to the oxidation ditch trains (Lakeside Equipment) with covered rotary aerators. “The bugs grab the phosphorus and eat the waste and do all the things they do, and then it’s on to the clarifiers,” says Wiesner.

Automated control of the aerators by way of variable-frequency drives keeps dissolved oxygen in the ditches at 2 parts per million. “We have DO probes in there,” says Wiesner. “If the DO drops below 2, the aerators speed up. If it rises above 2, they slow down.”

The new clarifier includes features Wiesner suggested. It is configured for easy cleaning with a single, wide concrete weir channel around the perimeter. “The channel is easy to access,” says Wiesner. “There’s a safety rail attached to the wall. There’s enough headroom to clean the channel, and floating solids can’t get up around the back of the weir to cause problems.” Final effluent goes to a new and enlarged UV disinfection system (TrojanUV) before discharge to the river.

Solids side

Waste activated sludge from the aerated holding tank goes through a rotary drum thickener (Vulcan). The material is batch-thickened once or twice a week. Thickened material goes to the 250,000-gallon aerobic digester. Digested biosolids are pumped to a 1-million-gallon storage tank and ultimately land-applied by injection by Veolia Environment.

A new Allen-Bradley SCADA system with FactoryTalk software (Rockwell Automation) installed by Van Ert Electric gives Wiesner and Johnson a comprehensive view of plant operations around the clock. They can access the system anytime and check status and make system adjustments remotely.

The plant’s effluent performance has been consistent — BOD is typically about 3.0 mg/L and TSS generally below 2.5 mg/L. Phosphorus is the nutrient of concern. “We don’t have an ammonia limit,” says Wiesner. “It’s just the nature of oxidation ditches that they tend to remove ammonia down to non-detect levels. The Department of Natural Resources didn’t feel we needed an ammonia permit limit.”

Meeting the phosphorus limit has been somewhat challenging. “We’re still working to dial in the bio-P,” Wiesner said last September. “The plant is brand new, so we just need to be patient. We have the right environment for the phosphorus-accumulating organisms. We just haven’t had the time yet to grow them out. For that reason we still use alum for phosphorus removal. We expect to reduce our alum use and ultimately eliminate it, but keep it available as a backup.” Typical effluent phosphorus is 0.5 mg/L.

The plant also has an effluent copper limit of 17 µg/L. “Due to the extreme soft water we have in this area, the DNR thought copper toxicity might be an issue,” says Wiesner. “That’s mostly controllable through the water distribution system. If they keep the pH high enough in the system so that the water is not aggressive to copper pipes, the copper stays out of the water.”

Helping to keep the process consistent is a Hach WIMS (Water Information Management Solution) brought to the table by Veolia. “We can track BOD, TSS, mixed liquor suspended solids, sludge volume index and whatever parameter we want,” Wiesner says.

Caring for collections

Wiesner and Johnson are responsible for the collections system, built in 1996. It includes 11 miles of piping and four lift stations with pumps from Flygt – a Xylem Brand. “We have a maintenance agreement with Flygt,” Wiesner says. “Once a year they pull the pumps, change the antifreeze and check them over.

“We do flushing of the collections system. From our low I&I, we can tell the sewers are in pretty good condition. The plan is to video them in the future to establish a baseline and catch problems before they develop.”

Wiesner credits success with the facility to the support received from the Ho-Chunk Nation: “They had the foresight to look at their needs and design a facility to meet them.”