Win-Win: Biosolids Program Holds Down Solids Management Costs and Delivers Quality Product to Farmers

Orem’s award-winning biosolids program delivers a quality product to farmers while holding solids management costs down.

Win-Win: Biosolids Program Holds Down Solids Management Costs and Delivers Quality Product to Farmers

Dan Shorten adjusts the dosing of polymer (SNF Polydyne) in the press room. 

The Orem, Utah, biosolids operation enjoys the best of both worlds — maybe the best of many.

The treatment plant’s old but well-maintained dewatering system produces a 15 percent-solids cake. All biosolids are applied on area farms, and there are more takers than the plant can supply. In addition, land application saves the city about $150 a ton versus landfilling.

Not too shabby. And Orem won the 2017 Outstanding Biosolids Program award from the Water Environment Association of Utah. “We’ve won the award before, but it’s always exciting to get it,” says Giles Demke, water reclamation manager. “We have a good operation.”

Demke credits Dan Shorten, senior biosolids plant operator, and his staff for their professional approach: “They do a great job testing the solids application to the fields and making sure we meet all the requirements. It’s very beneficial to the farming community south of Orem.”

Growing community

Orem’s 13.7 mgd (design) water reclamation facility serves about 95,000 people in Orem, along with customers in parts of the neighboring towns of Lindon and Vineyard. The community, about 40 miles south of Salt Lake City, has grown rapidly in recent years with the development of technology companies and the expansion of Utah Valley University.

The facility was upgraded in 2012 from its previous dual-train trickling filter and conventional oxidation ditch layout to the current biological nutrient removal configuration. The $14 million project converted the two ditches to phosphorus and nitrogen removal, added a third BNR oxidation ditch, increased settling capacity to relieve a hydraulic bottleneck at the secondary clarifiers and changed the disinfection process from chlorine to UV (SUEZ). Daily flow averages about 8.5 mgd. Effluent is discharged to Powell Slough and then flows about a mile to Utah Lake.

On the biosolids side, a thermophilic digester was added alongside an existing mesophilic unit, and former aerobic digester basins were converted to solids holding tanks.

Double digestion

Waste activated sludge is thickened in dissolved air flotation units and then pumped to the equalization tanks, where it is mixed with primary sludge and grease. In the thermophilic digester, the material held for about nine days at 120 degrees F and then held for up to 14 days in the mesophilic unit at 100 degrees F. “With the two digestion stages, we get better volatile solids reduction,” Shorten says. “We could go to Class A biosolids in the future.”

Biogas is captured and used to heat the digesters. The plant has a methane gas boiler and a natural gas boiler for backup and supplemental heat. Unused methane is flared off using a Groth candlestick flare, but that amount is minimal.

Digested biosolids are collected in the holding tank over weekends and fed to two belt presses (Alfa Laval Ashbrook Simon-Hartley) during the day shift Monday through Friday. “After pressing, we fill a dump truck with cake and then store the material on drying beds,” Shorten says. The facility produced about 6,300 tons of biosolids in 2018.

The plant’s six drying beds provide more than enough storage area for normal operation, with some extra space for periods when biosolids can’t be hauled because of weather. City trucks transport the cake to farmers’ fields, and while that represents some cost to the utility, Shorten points out that it’s much cheaper than landfilling the material.

“The biosolids are free to the farmers, but it’s pretty beneficial for both of us,” he says. The utility’s costs for fuel, truck maintenance and soil testing run to about $1.25 per ton, versus more than $25 a ton in tipping fees at the local landfill. “The farmers don’t pay us, and we don’t pay to get rid of it,” Shorten says. “We’re both pretty happy.”

Keeping them running

While much of the biosolids train is relatively new, the dewatering presses are real veterans, dating back 23 years. The key to their continued success is diligent maintenance. “They’ve been great,” Shorten says. “We’ve hardly done anything to them since they were installed in 1995. We operate them at anywhere from 200 and 240 gpm. We’ve hit 300 gpm at times but that’s really slamming them, and we try to avoid that.”

He says visitors to the plant, some from overseas, always marvel at the dewatering equipment’s durability. Cleaning the belts after each shift is critical. At some point, the belts become worn and need replacement, but other than that and a single gearbox and motor, the units have been essentially maintenance-free. Orem crew members keep the equipment greased and fix any leaks as soon as they occur.

“Our long belts have averaged about three years of service, the short belts about a year,” Shorten says. “On our short belts, we replace the wires that hold the belts together as soon as they’re broken. This prevents tearing and has allowed the belts to last longer. On the longer belts, we replace the wires about once a year.”

Orem’s two biosolids operators share tasks: one operating the presses, while the other tends to maintenance and other work. They rotate weekly. The team has experimented with dewatering polymers and determined that a polymer from SNF Polydyne works best.

To the fields

The farms lie 10 to 20 miles south of the city; farmers spread biosolids on fields averaging 20 to 30 acres. Crops include grass hay, alfalfa and in some cases silage corn. Orem requires proper spreading methods and approved equipment. About half a dozen farms take part at any one time.

Shorten says some farmers have reported yields of 1.5 to 2 times greater than they achieved with conventional fertilizers. “Our farmers are close to neighbors,” Shorten says. “Some live right in the middle of their fields. We’ve never had complaints — no flies, no odors, no nothing. Usually, the demand for the biosolids is more than we can supply.”

The Orem staff conducts the necessary soil testing. Team members test the soil at depths of 1 to 5 feet at several points, depending on the acreage. “We check for nitrates, phosphorus and ammonia in the soil. We also test the biosolids for nitrates, phosphorus, total nitrogen, fecals, metals and chelation.”

The samples are submitted to Brigham Young University Environmental Analytical Laboratory, American West Analytical Laboratories and Richards Laboratories of Utah for verification of 503 regulations. None have ever exceeded regulatory levels.

The program was a natural for the Water Environment Association of Utah biosolids award. The criteria include beneficial reuse of biosolids, percent of biosolids reused or recycled, maintenance, operations, absence of odors or other complaints, recordkeeping and application site management.

“After reviewing a couple of programs, I voted for the Orem Water Reclamation Facility,” says Weston Gardner of South Valley Water, one of the award reviewers. “They maintain an in-depth and detailed logbook of the locations where the biosolids are being applied and the test results of each load. They’re also creating lasting relationships with the farming community.”

Looking ahead

Orem’s program does face challenges, and one of them is demographics. “This area is growing like crazy,” Shorten says. “We’re seeing a lot of farm fields being converted to housing and commercial developments. Farmland could disappear.”

Accordingly, Orem is considering major upgrades to its biosolids system and less reliance on agricultural use. The utility is looking at changing to Class A biosolids and converting its dewatering operation to screw presses to save on energy and increase cake solids. That would reduce storage space requirements.

“We could sell the Class A biosolids as a fertilizer, or keep it and give it to the city’s parks department for use on green spaces and golf courses,” Shorten says. “I think eventually we’ll go to Class A, but it’s several years down the road.”

In the meantime, Orem will continue to provide biosolids to the farming community, with award-winning results: “We’ve worked with these farmers for a long time. Once in a while we’ll add someone new, but normally we get more requests for than we can fulfill. One farmer had his crops grow so much that people would drive by and ask what happened. The fields really took off. There was no odor. It spoke to the quality of our product.”

Down on the farm

How do farmers like using biosolids from the Orem Water Reclamation Facility? “It’s good for our crops, good for the environment and good for the citizens of Orem,” says J. Lynn Partridge, who farms 300 acres. He’s been farming all his life and is close to retirement.

It’s not just that it’s “a lot better to go green,” in his words. He has seen an increase in crop production with the biosolids after just over a year in the program. He reports a 1.5-ton-per-acre increase in hay production on the first cutting.

Partridge takes loads of biosolids in the spring before hay is planted, in the summer between cuttings and in fall after harvest. He uses a 5-ton John Deere articulated truck with a hydraulic gate to apply the biosolids, mechanically scattering material on the fields to let it dry a little more. Eventually he discs it into the ground.

He prefers the biosolids to commercial fertilizer, which is more likely to leach into water sources. The organic matter in biosolids makes the soil healthier, he says. “We see earthworms and benefit from the soil aeration they provide.”

Partridge enjoys the staff from the Orem plant: “They’re excellent to work with. In fact, one of them used to work in farming. They understand what our needs are.”


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