News from Schwing Bioset

Schwing Bioset Process Helps Community Maximize Beneficial Reuse

 

Written by Larry Trojak, Trojak Communications

Version also published in TPO Magazine, February 2019

 

Too Valuable to Waste

A lime stabilization process helps an Arkansas city meet its goal of producing Class A biosolids to enable the resumption of beneficial use. 

The strength and resilience of the wastewater treatment industry can often be found in the innovative solutions brought to bear to address the challenges it faces. And those solutions are not being employed solely by WWTPs in big cities or even larger municipalities, but often by small or mid-size operations — entities like the Russellville (Arkansas) Pollution Control Works Facility, for example. Faced with a situation in which they could no longer land-apply their Class B biosolids, plant officials looked for alternatives and opted to upgrade their operation to create a Class A product. In doing so, they’re finding value in their byproduct and have eliminated the need to simply waste it or — as they’ve reluctantly done in the past —  landfill it. A big solution from a smaller operation? Not surprising at all.

 

Snapshot: Russellville 

Located midway between Little Rock and Fort Smith, Ark., the city of Russellville is home to several major manufacturing facilities as well as the state’s only nuclear power plant. Owned and operated by Russellville City Corporation, the city’s Pollution Control Works Facility (PCWF) serves a population of 30,000 including all of Russellville and the nearby town of Dover. The wastewater collections system consists of roughly 170 miles of gravity sewer, 18 lift stations of various pumping capacities, and 14.1 miles of force main. Approximately 9,000 homes and businesses, and the service lines connecting these homes and businesses constitute an additional 129 miles of sewers — all of which terminate at the PCWF.

According to Randy Bradley, the facility’s wastewater operations manager, the plant has undergone periodic updates in its 55-year history, but really made a seismic shift in its approach a couple years back.

“Up to that point — and still to a large part today — we were a fairly typical operation,” he said. “The plant is designed for 7.3 mgd, and once wastewater gets here, it first goes through some Duperon bar screens to remove plastics and other products that can’t be broken down in normal treatment. After the screens, it undergoes grit removal and is pumped back through the plant where it goes through the primary clarifiers, then to one of three aeration basins — two 450,000 gallon tanks and one 850,000 gallon tank — and into the final clarifiers. A final stop in a chlorine contact chamber allows us to inject some sulfur dioxide to meet the non-detection limit of chlorine just before it is discharged.”

 

Change in Plans 

In the past, the facility’s primary sludge and the waste activated sludge from the aeration basins was pumped into a digester, then through a belt press for dewatering and deposited onto trucks that would take it for land application on several pieces of permitted property.

“However, in 2014, land ownership changed on one of those parcels and the new owners no longer wanted sludge on their land. So, we lost that piece of property, which was a substantial loss in available area, and were restricted solely to the parcel we owned. At that time, we were generating about 2400 lbs. per day of the Class B biosolids. Ordinarily, we might have been able to make that work, but, at the time, we had just added another aeration basin and clarifier to the front end of the process, so we knew we were going to be generating more solids. Something had to be done.”

Schwing Bioset Class A Biosolids Process 

Seeking Alternatives

Faced with that situation, the facility conducted an intensive study to look at the options available to them. Those included: increasing the digester volumes or improving the existing ones, composting, and the use of sludge dryers.

“What turned us off to drying the sludge was the significant initial investment,” said Bradley. “And, as I talked to people at other facilities, I discovered that there is a fairly high cost for maintenance on that equipment — that’s a one-two punch we didn’t need. And when we went to a northwest Arkansas composting facility, we found that solution to be very labor-intensive and would demand much more acreage than we had available. Couple that with the fact that we weren’t certain we could ensure a reliable availability of the organic material needed for the process and it was no longer a serious choice. We needed another viable option and learned about it almost in our backyard.”

 

A Good Tip

At about that same time, the Russellville facility was encountering issues preventing them from maintaining the necessary retention time in their digester to meet Class B specifications, forcing them to truck their biosolids to a nearby landfill. It was a situation that ran counter to everything Bradley and his team stood for.

“We absolutely hate to have to send anything to landfill, and not just because of the costs involved in doing so — though those costs are substantial,” he said. “Landfills have space issues of their own and this is material that can ultimately serve a better benefit. But yet, we were at a point where we had no choice, so we contracted with Denali Water Solutions (Russellville, Ark.) to haul off our sludge. It just so happened that they’d been working on some potential projects with Tom Welch, a regional manager from Schwing Bioset, Inc. and told us about the Schwing Bioset process for creating a Class A biosolid.  After contacting SBI, we were intrigued enough that I, along with Lance Bartlett our utility engineer, and Chesley Jackson my senior operator, took a trip to St. Petersburg, Florida to look at their process in operation and saw the possibilities it held for us.”

In the context of what PCWF’s current solution looks like, the Schwing Bioset process to which Bradley refers, starts by taking biosolids that have been dewatered in a BDP 1.5-meter Model 3DP three-belt press and gravity thickener (at PCWF, dewatered to about 18% dry solids) and dropped into a hopper with a twin-screw mixer in which quicklime and sulfamic acid are added and blended. The mixing effort helps alleviate issues such as unreacted lime in the final product — and the costs associated with it. A Schwing KSP-25 piston pump then sends the blended material into the 35 ft. long reactor where temps in the 140° F range from the acid/quicklime mixture raise the pH level, stabilize the biosolids mixture, and produce the Class A product PCWF needs.

Schwing Bioset Pump and Reactor 

Built for Expansion 

Getting to the point where the Schwing Bioset process was fully theirs and fully online, was something of a departure for all parties involved. According to SBI’s Tom Welch, in a deal that involved the plant’s owners, SBI and Denali Water Solutions, a mobile Bioset system was brought to Russellville to initiate a pilot program in order to prove out the process there.

“The final agreement involved us leasing our mobile Bioset system to Denali which they, in turn, operated for the facility, disposing of the material at an onsite dirt yard. Denali charged City Corporation, the owners and operators of the PCWF, a monthly fee to cover the labor, operation, and lease of the Bioset equipment. However, after the final equipment was purchased and the installation was nearing completion, facility management determined that they had the comfort level to operate the system and manage the disposal of the product themselves. That made good sense since bringing that process in-house would save them a large operating cost.”

Bradley added that the installation process itself was relatively quick and efficient. “Largely due to the help SBI provided — technicians spent the first two weeks with us — the install was very smooth,” he said. “During the design phase, we gave Ft. Smith-based Hawkins-Weir Engineering a projection for where we might be in 10-20 years and they designed the facility for future area development. As a result, the Bioset reactor is sized to handle two belt presses, so, if growth warrants it, we can just move another belt press in without skipping a beat.”

 

Great for the Soil

PCWF went online with the new system in 2016 and has been processing, on average, 81,000 lbs. of Class A biosolids per month since. Once the material exits the Bioset process, it is loaded onto dual axle dump trucks and taken out to an area adjacent to the plant, spread out using a front-end loader and allowed to dry. Once dry, it is moved into piles and — after periodic testing for salmonella — given away to area farmers. 

“We have several farmers competing for it at times, which is great for us,” said Bradley. “While the material has some nutrient value, its ability to boost the pH of soil is its real selling point. Almost all the soil in Arkansas is pretty acidic, so it welcomes that pH boost.

Next spring we are looking at possibly doing some type of bid for it. Simply recouping some of our costs — even enough to pay for fuel for the loader, example — would be a nice bonus. But right now just having someone haul it off for us is and make good use of it a huge improvement over what we did in the past. This entire project could not have gone better nor had better results.”

 

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Tags: Class AA/EQ Biosolids, Lime Stabilization, Beneficial Reuse, Bioset Process

Bioset Demo Confirms Direction for New Class A Biosolids Equipment at Russellville WWTP

 

Written by Lance Bartlett, Utility Engineering Manager for City Corporation and Tom Welch, Southeast Regional Sales Manager for Schwing Bioset, Inc.

April 25, 2016

 

In early 2015, City Corporation, the commission established by the City of Russellville to operate the municipal water system, completed a construction project to abandon existing fixed film treatment facilities and convert the wastewater treatment plant to a denitrifying activated sludge facility.  Activated sludge technologies produce more sludge than fixed film and initial calculations predicted an increase of 6 to 7 times the current production rate when operated at the design capacity of the facility.

City Corporation had processed sludge through aging aerobic digesters and produced a Class B biosolid under 40 CFR 503 that was then dewatered and land applied to three nearby fields.  Two of the three permitted fields were no longer available, leaving only 49 acres for use.  The increase of sludge production was predicted to require around 160 acres.

The expected increase in sludge production and lack of land available for land application prompted staff to explore options.  The alternatives explored included composting, additional aerobic digesters, dryers, and the Bioset process from Schwing Bioset, Inc. (SBI). The Bioset process was selected for piloting in February and March of 2015 due to its low cost, simple operation, and the high quality Class A product that it produces.  The lone concern was with respect to the increase in volume due to the addition of chemicals, and staff wanted to get the new process up and running to obtain empirical data on sludge volume.  The engineering firm performing the preliminary study had built in a large contingency due to not being familiar with the Bioset technology and the uncertainty in sludge volume, thus raising concerns that the Bioset technology would be the proper process for the future of the Russellville WWTP.  Ultimately the volumetric increase was less than 10%, and with the Class A designation the number of outlets and demand for the material exceeds production rates.

Russellville_Bioset_3.jpg Russellville WWTP_Bioset Process_Schwing Bioset

Following that successful pilot test, in April of 2015, Schwing Bioset agreed to continue to lease the pilot machine under a monthly contract basis for the sludge handling process.  By the fall, City Corporation had a good feel for their solids production and had a great experience with the Bioset full scale pilot equipment.  Given the years of struggling with the Class B sludge process, management and staff were very pleased with the Class A process and end product and the thought of returning to a Class B process was taken off the table. With all the uncertainty taken out of the equation, staff was ready to make a decision and chose to move forward with a permanent Bioset installation.  City Corporation and Schwing Bioset continue to operate under a contract that allows City Corporation to operate the pilot unit until the permanent unit is installed and operational.  This arrangement allows City Corporation to manage their sludge and operate the plant in accordance with the design parameters, keeping the facility in compliance with the ADEQ, which otherwise would not be possible.  The new facility is anticipated to be operational in mid-October 2016.  The current digester will only be used as a sludge holding tank, thus reducing the power consumption needed for complete aerobic digestion to meet Class B standards, and allowing just WAS sludge to be converted to Class A EQ fertilizer through the Bioset process.

To learn more about our Bioset process or this project specifically, contact this blog’s author, Tom Welch, and/or visit the SBI Bioset Process page. For other inquiries, call 715.247.3433, visit our website, or find us on social media.

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Tags: Bioset Process, Class AA/EQ Biosolids, Wastewater Treatment, Lime Stabilization, Bioset Demo

At Home on the Range

By Larry Trojak - October 2012

TPO

Though well past its boom times as a supplier of iron ore, the Iron Range area of northeast Minnesota enjoys a rich history and a fairly stable economy.

Three small Iron Range communities rely on the 0.5 mgd (design) wastewater treatment plant that bears their communities' names. The Coleraine-Bovey-Taconite Wastewater Treatment Facility nears its 25th anniversary having completed an expansion that includes a shift from Class B to Class A biosolids using a lime stabilization process.

The new process resolved a long-standing issue with meeting U.S. EPA standards for volatile solids reduction during the region's long, often frigid winters.

History of beneficial use

The CBT plant takes in wastewater at a main lift station with three Hydromatic pumps (Pentair) plus an overflow/bypass lift station with a Flygt pump (Xylem). From there, the flow enters an automatic bar screen (Parkson) and an aerated grit chamber that removes screenings and debris via a grit pump and classifier (Weir Specialty Pumps/WEMCO Pump).

Wastewater then passes through a Milltronics OCM III ultrasonic flowmeter (Siemens) to secondary treatment in two activated sludge tanks with Sanitaire fine-bubble diffusers (Xylem), and on to two secondary clarifiers (Walker Process). The waste activated sludge from the clarifiers is pumped to an aerobic digester with fine-bubble diffusers (also Sanitaire).

Secondary effluent is sent through a chlorine contact tank (Wallace & Tiernan), where chlorine and sulfur dioxide doses are fed automatically based on flow proportion. After dechlorination, the effluent travels to an effluent lift station (Hydromatic/Pentair) that pumps it 3.5 miles to the Swan River.

After a 40-day retention time, the solids are pumped to a belt filter press (Parkson) for dewatering and then to a reactor (Schwing Bioset) to produce Class A biosolids.

Before the recent expansion, dewatered biosolids were simply land-applied on area farms. "That was what we did from the time we opened in 1987 until about 1997, when the Minnesota Pollution Control Agency (MPCA) adopted the U.S. EPA regulations and changed the way we managed our biosolids," says Vernard Hawkinson, plant supervisor.

Part-time tundra

Iron Range winter temperatures can be challenging: In and around the town of Coleraine, average lows between November and February are near zero degrees F, and the thermometer once hit a record 51 below zero. For treatment plant operators like Hawkinson, that can be a logistical nightmare.

"The changes to federal EPA guidelines essentially made our whole biosolids process non-compliant during winter months," he says. "That process depends upon bacteria doing their job to reduce the volatile solids content in the biosolids to the level needed for producing a Class B biosolid.

"They do that just fine, except in extremely cold temperatures. When the rules were adopted, we had to meet the minimum 38 percent volatile solids reduction, or other options that were acceptable to meet the Vector Attraction Reduction rule. We were no longer in compliance during the winter, so we had to start taking steps to correct that."

One alternative approach CBT took was to stockpile the dewatered material during winter and then, when it thawed in spring, make it available to area farmers, who had to apply it to their land immediately and incorporate it into the soil. That too, had its problems, says Hawkinson.

"For one thing, because of the climate here, sometimes the biosolids piles would not thaw until the end of May, and most farmers wanted their planting to be done by then, not just starting," he says. "We did that for a few years before deciding it would be better to simply haul the liquid material to the Grand Rapids wastewater plant, or take the dewatered material to their landfill. Unfortunately, they were less-than-receptive to those plans on a long-term basis and we found ourselves back at square one."

Toward Class A

Hawkinson made other efforts to comply with the MPCA and EPA rules. Those included achieving the 38 percent volatile solids reduction using the approximate mass balance equation, and conducting a Bench Scale Analysis and Specific Oxygen Uptake Rate Analysis — all to no avail.

One solution that came to the forefront was to add a second digester. "That seemed like the only recourse we had at the time," says Hawkinson. "Adding a second tank would afford us the extra digestion time we would need to reduce the volatile solids. So we found an engineering firm to tackle the project.

"Their initial estimate came in at about $700,000 for the second digester, and the design process was started. Unfortunately, as the project progressed, additional site work was determined to be necessary which, through no fault of theirs, escalated the cost to roughly twice the original estimate."

bioset process

During that same time, Hawkinson attended a seminar put on by the Minnesota Rural Water Association at which representatives from Schwing Bioset presented their biosolids treatment process. Intrigued, Hawkinson spoke to a company representative at the show. After back-and-forth talks, Schwing Bioset estimated an installation at CBT would cost about $700,000 — the same as the original estimate for the digester — and the end product would be Class A biosolids.

"That made good sense to us on many levels, so we cancelled the digester design project and committed to Bioset," says Hawkinson.

 

Just add lime

The Bioset process mixes biosolids exiting the dewatering belt press (with a solids content of about 15 percent) with quicklime and sulfamic acid using a twin screw feeder. Then, using a Schwing KSP-5 pump, the mix is delivered under pressure through an insulated reactor. The enclosed process contains dust and odors while maintaining a constant temperature of 158 degrees F for at least 30 minutes to ensure that all pathogens are neutralized.

Working with the U.S. EPA Pathogen Equivalency Committee (PEC) through the Process to Further Reduce Pathogens (PFRP) treatment process in the 503 regulations, Schwing Bioset has obtained approval for the Bioset process to operate at 131 degrees F, provided the ammonium concentration within the reactor is above 0.5 mg/g dry weight. This offers a significant reduction in chemical usage from the standard 158 degrees F operating regime and translates into an approximate 30 percent reduction in operating costs.

The system at CBT also includes a recirculation feature in which biosolids that have not achieved the necessary temperature on startup are returned to the hopper for reprocessing. Upon exiting the Bioset process, now with a solids content in the 35 to 38 percent range, the Class A biosolids are discharged to a 48- by 75-foot storage building, constructed at the time of the biosolids upgrade. The plant produces about 35 dry tons of biosolids per year.

Popular with farmers

"We now have an excellent product with an effective acid neutralizing power of approximately 64 percent of pure lime," says Hawkinson. "Farmers in the area, who see the product as a great way to raise the pH levels of their soil, have agreed to take as much as we can produce.

"That's a far cry from having to actively seek a place where we could take it. Right now, we only need to rely upon the Bioset process for half the year — we get the volatile solids reduction we need in warmer weather. But it is an excellent alternative, and it has allowed us to create a Class A biosolid with the same outlay we would have incurred for the Class B product. It has really worked out well for us."

Tags: Class 'A' Biosolids, Bioset Process, Wastewater Treatment, Lime Stabilization

Generating "Revinu"

Lime stabilization is a proven, EPA-approved method for treating sewage sludge. In the capable hands of Schwing Bioset, the technique of lime addition has gone from effective to exceptional.

Bioset's process optimizes the chemical requirements and system efficiencies of lime stabilization. The end product, called Revinu, is safe and has many uses including fertilizer and as a soil stabilizer. Revinu is inexpensive and reliable, and produces a readily usable and valuable Class AA product.

affordable fertilizer-Revinu

Compared to other methods of producing Class AA material, the Bioset process is affordable from both initial capital expenditures and ongoing operation and maintenance costs. The equipment is fully automated and requires very little operator time. As a Class AA biosolid, the end product can be widely used and handled without many of the restrictions imposed on a Class B product.

Revinu's nutrient composition is a strong selling point. First, Revinu's low phosphorus content means it can be applied in phosphorus-sensitive areas. Second, Revinu provides a slow-release alternative to commercial nitrogen, which gives consumers three times the amount of nitrogen breakdown for prolonged plant nutrition. Third, Revinu provides sufficient potassium-a nutrient that is often prohibitively expensive-to support root growth and proper seed germination for a fraction of the market price of potassium.

Finally, Revinu is made up of 35% to 55% organic humus. The humus in the material acts as a topsoil, replenishing the natural bacteria that are essential for optimal plant growth and root strength. Until Revinu arrived on the market, landowners were often unable to replace eroded topsoil due to the astronomical cost associated with the process. Revinu makes topsoil replenishment accessible and affordable.

In short, the Bioset process is the most versatile and attractive method for biosolids treatment on the market today.

Tags: Bioset Process, Class AA/EQ Biosolids, Biosolids, Wastewater Treatment, Fertilizer, Lime Stabilization

Stewartstown Installation

July 2008

Schwing Bioset is pleased to announce the start-up of the new Bioset Class A lime stabilization system at the Stewartstown STP in Stewartstown PA. Stewartstown is a growing community between York, PA and Baltimore, MD.

Like many communities, Stewartstown understands the importance of beneficial reuse but was concerned with odor issues due to the proximity of residential areas near the plant. The key features that attracted Stewartstown to the Bioset process were the odor control, dust control and the flexibility to design the equipment to fit into their existing available space. The process is fully enclosed containing odors and dust during treatment. The technology is also compact and was customized to fit in an existing garage bay, eliminating the need for additional structures or odor control equipment.

The low maintenance and operating cost along with the overall system reliability prove to be an excellent solution for Stewartstown to consistently produce a product that is safe, inexpensive, and in demand.

Stewartstown Installation

Tags: Biosolids, Bioset Class A, Schwing Bioset, Lime Stabilization