The Ishpeming Area Joint Wastewater Treatment Facility in Upper Michigan is a popular place. Next-door neighbor Negaunee is about to send its wastewater to the plant for treatment. The facility’s Class A Exceptional Quality biosolids compost is in demand for local landscaping. And its staff loves working at the plant because several process improvements have made operations easier and safer.

In part, facility director Debbie Pellow attributes the plant’s success to its administrative structure, consisting of a board that deals only with wastewater. “We supply treatment to the City of Ishpeming and to Ishpeming Township and are governed by the Ishpeming Area Joint Wastewater Treatment Board,” Pellow says. “Our board members must apply for the position. They bring an inherent interest and understanding for wastewater to the job. As a result, our board emphasizes keeping our employees safe.”

She says staff members like their jobs and tend to stay on for the long haul. Pellow has been at the plant since 1992. Paul Altobello, lead operator, and Mike Junak, operator, have been there since 1991, and Darren Kotajarvi, operator, since 1994. The staff also includes Marc Hillman, operator, and Melissa Richards, lab technician. “Absolutely, it’s a great place to work,” says Altobello.

Effective removal

Opened in 1986, the Ishpeming plant handles an average flow of 1.0 mgd and is designed for 2.34 mgd. The plant accepts wastewater from the City of Ishpeming (population 6,470) and Ishpeming Township (population 3,522). The city and township maintain their own collection systems: “We’re responsible for it once it hits the gate,” says Pellow.

Wastewater flows by gravity to a wet well 23 feet below plant grade and is pumped in a single stage up to the headworks by four 50 hp pumps (Fairbanks Nijhuis). A center-flow band screen with 3/8-inch openings (Ovivo) removes rags and trash. An aerated chamber removes grit. Ferrous chloride is added to remove phosphorus, enabling the plant to meet a stringent phosphorus removal standard for its receiving stream, the Carp River, classified as a sensitive trout habitat.

There are no primary clarifiers. After the headworks, the flow passes to a pair of horseshoe-shaped oxidation ditches, each one rated at 1.1 mgd. The ditches (Ovivo) are equipped with four surface aerators with mechanical splash dual impellers. Allen-Bradley variable-frequency drives (Rockwell Automation) control the aerators according to the dissolved oxygen content in the ditches. Return activated sludge (moved by Fairbanks Nijhuis pumps) mixes with influent at the head of the biological process.

“Normally, we operate one ditch at a time, but with the Negaunee wastewater coming on stream, we may need to operate both,” says Altobello. Treated water flows to two new clarifiers with full-radius skimmers and energy dissipating feed wells, each 65 feet in diameter.

In the chlorination/dechlorination chamber, oxygen is added before the flow passes to the river. Ishpeming uses hypochlorite for disinfection and sodium bisulfite for dechlorination. Some of the effluent water is used in the plant; in fact, the plant uses city water only for drinking, showers and washing.

The wastewater treatment process achieves high levels of removal — 95 percent of BOD and TSS, 85-plus percent of phosphorus and essentially complete ammonia removal. “Our nitrification performance is unbelievable, especially considering our cold climate,” says Altobello. All of the treatment processes are covered. The average lows in January and February are -5 degrees F, and the city’s monthly record lows for November through March are all well below zero (the coldest ever recorded was -34 in 1979).

From sludge to compost

Settled solids from the process pass to dissolved air flotation thickeners, and the thickened sludge (2 to 4 percent solids) is pumped to one of four aerobic digesters. “Anaerobic digestion would convert most of the organics to create methane,” explains Altobello. “We need the organics as fuel for the composting process, so we use aerobic digestion for the waste solids. We want as much organic content in the solids as possible.”

A pair of 1-meter belt filter presses (Ashbrook Simon-Hartley) dewater the biosolids — dosed with a polymer — to about 15 percent solids. The pressed cake is mixed with wood chips, then placed in an in-vessel composting system (Engineered Compost Systems). The system is housed in a separate building with five composting bays (vessels), each 12 feet high by 14 feet wide and about 50 feet long.

An RSview32 SCADA system (Rockwell Automation) enables the plant staff to automatically monitor and control the processes, and the composting system is connected directly to Environmental Composting Systems in Seattle, Wash., so that both the plant staff and company technicians can monitor the composting time and temperatures.

Continuous improvements

The plant’s sterling performance and operator satisfaction result from a number of process improvements, some suggested by the staff, others emanating from inspections by Michigan OSHA (at the plant’s invitation), and all supported by the wastewater board.

“When our operators come up with a better way of doing something, we give it very serious consideration,” says Pellow. She points out that with a 23-foot-deep wet well, cleaning with hand rakes was difficult. In 2007, the board authorized $200,000 to install an automatic influent screening system. “We don’t have to haul buckets up 23 feet anymore,” says Altobello. The screen comes all the way up to the headworks floor, eliminating the need for operators to enter a confined space.

In the blower room, once a very noisy place, staff members now can hear themselves talk. That’s due to the recent addition of positive displacement blowers (Kaeser) and noise enclosures. The room is so quiet now that a recent Michigan OSHA inspection determined that ear protection was not required.

Because the April 2013 OSHA inspection was voluntary, the plant was able to correct safety issues without being assessed penalties. “We found the money necessary to act on the recommendations resulting from the inspection,” says Pellow. “They recommended several safety steps, including different types of ladders for entry into our digesters.”

The old ladders were a short step-ladder type. OSHA recommended longer, more stable ladders with safety chains, and the team made the switch, adding to a positive, safe environment for employees. The facility hasn’t recorded a lost-time accident in more than 27 years.

Operators had a hand in two other significant changes. “We wanted a better skimming system on the clarifiers,” says Altobello. “The old ones didn’t skim the full radius of the clarifiers, and the water just didn’t look good.” Skimmers now sweep the entire surface of the clarifiers. The facility has combined shifts so that a full crew is on hand during the day. “It makes it easier for us to get big projects done,” Altobello says.

An excellent product

The Ishpeming staff members are fond of the in-vessel composting system. Since startup in February 2011, it has proven simple to operate and environmentally friendly. “There are just two little blowers to maintain,” says Altobello. Adds Pellow, “It’s the right thing to do for the environment.”

Ishpeming’s is the only all-weather in-vessel composting system in Michigan and one of just two like it nationwide. Dewatered cake and wood chips are mixed to reach a density of 29 to 34 pounds per cubic foot of material. Then the mix is allowed to “cook and cure” in the site-built insulated concrete vessels.

Temperature probes are inserted into the inside walls of each composting bay. The composting atmosphere is tightly enclosed, and the heavy, pressurized bay doors are opened with a special hydraulic system supplied as part of the technology. The doors are lifted onto an overhead track and slide from side to side to open the vessel completely and avoid damage to the door as material is unloaded.

The aeration components and control system are located at the backs of the vessels in an aeration hallway. Heat from the vessels keeps the hallway warm even in extreme cold. The control system closely monitors the process and, along with a unique aeration design, optimizes compost stabilization and pathogen reduction.

The material heats to 131 degrees F or higher for three straight days with no breaks to ensure the required pathogen reduction. The material must also maintain 113 degrees F for 14 nonconsecutive days to meet vector attraction reduction requirements. The total process takes about 50 days and yields a product that achieves Exceptional Quality (EQ) status.

After the cure cycle, a Trommel screen (Screen USA) removes the larger wood chips, which are simply recycled and used in the next batch. Ishpeming generally fills two bays each month. In winter, the cured compost is stored in a covered barn-like building. In the warmer months, it is sold to residents for gardening and landscaping. Any remaining product is taken by Moyle Trucking, a local landscaping firm.

Moyle uses it for landscaping and top dressing of wildlife feedlots, according to Sean Francis, project manager with the company. “We blend the compost with topsoil — about 25 percent compost to 75 percent soil,” he says. “It adds nutrients to the topsoil. We’ve been using it for a couple of years now and it’s a good product. It’s good to put it to use.”

The system is highly cost effective versus Ishpeming’s old method of landfilling the sludge cake. The plant was paying $38.50 a ton in landfill tipping fees and about $60,000 a year in total landfill fees and hauling costs. With the tipping fees increasing to $58.50 per ton, the facility faced landfill costs of about $120,000.

“In contrast, our chip costs are about $45,000 a year,” Pellow says. “We were paying and paying and using up landfill space. Why produce a product and then not use it?” The savings have allowed the facility to act on yet another operator suggestion and obtain a second compost loader. “Now we can use one loader for screening and the other for loading the vessels,” says Altobello. “Plus we have one for backup if necessary.”

Negaunee next

The plant’s wastewater flows and compost production will soon increase significantly: Sometime in winter or spring of 2014, the facility will begin receiving wastewater from the neighboring city of Negaunee, bringing the average daily flow to around 1.5 mgd. Average design flow will be increased to 5.5 mgd, mainly by addition of a third clarifier and retrofitting and recommissioning of the plant’s two original clarifiers.

The agreement to send Negaunee’s flow to Ishpeming has been discussed for some time. A recent study of treatment options showed that complete rehabilitation of the Negaunee treatment plant would raise user rates from $21.26 to about $50 a month, and partial rehabilitation still would raise rates to more than $43 a month.

Sending Negaunee wastewater to Ishpeming will increase rates to $27.68 a month and capitalize on the $2 million already spent by Negaunee to accommodate the change. The switch will occur as soon as a new 5-mile feeder line from Negaunee is completed.

“This was the most cost-effective option,” says Pellow. Studies show a $336,000 annual savings in operations and labor costs for wastewater treatment at Negaunee, enabling the city to pay for its bonds for the Ishpeming connection with the savings. The move will also generate more revenue for the Ishpeming facility, reducing monthly payments from Ishpeming city and township. Says Pellow, “Having the three communities together will save everybody money.”