News from Schwing Bioset

Schwing Bioset Exhibiting at the 2015 Texas Water Conference


Posted on April 9, 2015

Schwing Bioset Screw Press

Schwing Bioset, Inc. will be exhibiting at the 2015 Texas Water in April in Corpus Christie, Texas.

Please be sure to stop by our booth (#1209) while you're on the exhibit floor.

Visit the conference website to view the event details and floor map:

We hope to see you there!




Tags: Events, Wastewater Treatment, Schwing Bioset, Pumps, Municipal

Schwing Bioset Secures Long-Term Trial with City of St. Petersburg


Posted on January 9, 2013

City of St. Petersburg upgrades biosolids treatment to Class AA/EQ using Schwing Bioset’s patented Bioset process. 

St. Petersburg, FL – Until recently, the city of St Petersburg, Florida’s Southwest Water Reclamation Facility relied solely on anaerobic digesters to stabilize their biosolids. However, the 20+ year old digesters had not only aged to a point of disrepair, but were beginning to cause odor complaints from the neighbors. Hence, the city felt the pressure to take corrective action quickly.

Not only would rehabilitating the existing digesters entail a sizeable expense, but in the end, the digesters would still only be producing a Class B product that needed to be hauled off to land sites. In the past this was not an issue, but the new F.A.C. 62-640 rule in Florida is going to make Class B biosolids harder to reuse in a beneficial manner.

Schwing Bioset brought in their mobile Bioset System to the St Petersburg facility in June of 2011 for a 5-day trial. Demonstrating their ability to use a natural process that eliminates pathogens by elevating pH and temperature, they proved their ability to create a Class AA/EQ product from the facility’s biosolids that would meet the 62-640 rule in Florida.

After successfully providing Class AA within 24 hours of setting up the equipment for the trial, the city engaged in an active discussion with Schwing Bioset to extend their trial to a full year. In this time, Schwing Bioset would be contracted to install all equipment, make sure operators were trained properly, and modify the city’s existing operation for a year-long period. Presently the equipment is operating successfully, the digesters are off line, the odor complaints have been eliminated, and the plant is producing Class AA/EQ biosolids that are being beneficially reused locally.

 class A for the price of class B

Tags: Bioset Process, Bioset System, Class 'AA' Biosolids, Biosolids, Wastewater Treatment

At Home on the Range

By Larry Trojak - October 2012


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

Southerly sets the standard with solids disposal efforts

Problem Solvers (as seen on

Problem: Increased solids volume after construction project increased overall capacity.
Solution: Pumps and sliding frames enable cake disposal.

The Southerly Wastewater Treatment Plant, which serves most of the greater Columbus, Ohio, area, recently completed a 5-year, $350 million expansion. The expansion nearly tripled its peak capacity from 431,500 to 1.25 million m3/d (114 to 330 mgd). The plant has earned numerous awards for plant and employee performance, but its solids disposal program truly makes Southerly a standout.

Using a quartet of heavy-duty pumps and a number of sliding-frame components from Schwing Bioset Inc. (Somerset, Wis.), cake can either be routed directly to incineration or sent to a pair of storage silos. Once in the silos, the material is available for truck loading and transport, either to an existing composting operation or directly to the landfill.

Change they can use

Centrifuges installed several years before the expansion successfully handle the increased flows to the solids handling area, according to Jeff Hall, assistant plant manager.

“That upgrade was implemented both to replace aging equipment, as in the case of the centrifuges, and to add functionality to other areas, like the transportation of solids,” Hall said. “In the past, primary solids were gravity-thickened while older centrifuges thickened the waste activated sludge [WAS]. The new units now thicken both the primary solids and the WAS. This new approach boosts the solids content of the resulting dewatered cake to about 20% to 25%, a nice improvement over the 17% to 21% solids content with the older system.”

Additional changes included installation of new cake pumps, a pair of storage silos, and sliding frames at two points in the solids handling process.

The routes to disposal

Southerly’s pumps and silos assist in transporting cake to several disposal options. As material exits the centrifuges, it is routed to any of four KSP 45V(HD)L-SFMS pumps, which route it either directly to the incinerators or to storage silos.

“Even though incineration is the most efficient method of disposal, we still try to keep the compost operation fed with as much as it needs, since that is the better use of the product,” said Carmon Allen, solids supervisor 2 at Southerly. The solids pumps at Southerly are designed to generate a force sufficient to move cake the long distances needed for either incineration or storage. It is approximately 91 m (300 ft) to the multihearth incinerators, which have operating temperatures of 760°C (1400°F), and about 122 m (400 ft) to the storage silos, Allen said. Equipped with a solids-flow measuring system, the pumps are able to measure to within 5% the amount of solids that are pumped to the incinerator. This simplifies the plant’s U.S. Environmental Protection Agency reporting requirements for the incinerator.

“Material headed to the silos, however, has an additional challenge to overcome,” Allen said. Once it reaches the base of the silo, “the cake has to go straight up another 100 ft [30 m] to enter the top of the structures, so the force needed to do that is really pretty impressive. I don’t think any regular equipment would be up to a task like that; these are definitely the right pumps for the job.”

Giving it the slip

Despite maximum operating pressures of 7585 kPa (1100 lb/in.2) for each pump, the extended distances at Southerly prompted Schwing Bioset to make accommodations to help move the solids along. The company added a pipeline lubrication system with a 360-degree annular groove that evenly injects a thin film of water around the entire annulus of the pipe. The water separates viscous and sticky materials from the inner wall of the pipeline. This reduces friction loss in the pipeline and lowers pipeline operating pressures by as much as 50%. This lubrication also means less energy use to move the solids and less wear on parts.

Parts such as the pumping rams, poppet valve discs, and seats are lasting for 6 months, said Tom Thomas, maintenance supervisor 2 at Southerly. “That’s about 4000 hours of wear-part life, which is outstanding, given what they’re being asked to pump.”

Silo efficiency

Prior to the installation of its two silos, Southerly relied upon a smaller holding vessel, a belt-fed, hopper-equipped component that used a series of screws to load trucks sitting under the discharge chute. City officials say the new silos are larger — providing about 75% more capacity — as well as far more efficient.

The new silos can load a truck in 5 minutes instead of the 45 minutes that was required before. Because the city pays a contractor to haul biosolids, reducing loading times lowers overall hauling costs. Trucks now spend more time hauling and less time waiting to be loaded. This means more trucks are loaded per day at a lower cost.

Inside the sliding-frame silo, hydraulic cylinders move an elliptical frame across the silo floor. The frame’s action not only breaks any bridging that can occur above the extraction screw, but it also pushes and pulls material toward the silo center for discharge. The cake then is fed into a twin screw feeder for discharge into trucks.

“Each silo holds better than 1500 tons [1360 Mg] of cake, so even if one of the incinerators went down and there was an interruption in the trucking operation, we’d still have a nice short-term storage option while things get back up again,” Allen said. “It’s really all about flexibility, and these silos afford us that.”

Due to the sheer size of the silos, each is equipped with three extraction screw conveyors at the bottom, enabling the trucks to be evenly loaded without having to be moved back and forth.

The silos also include an odor- and splash-control shroud that minimizes the need for odor control in the truck-loading building, reduces the chance of material splatter during loading, and confines any splatter to the area immediately adjacent to the trucks.

After loading, the solids are hauled either to a landfill or the composting operation. “Today, we are reusing about one-third of the solids we handle through the composting operation,” Hall said. “We are generating revenue from a product that was once simply discarded. However, it is also a plus from an environmental perspective. Any time you can reuse something rather than just burying it or burning it, you are making a positive impact.”

©2012 Water Environment Federation. All rights reserved.

Tags: Piston Pumps, Biosolids, Wastewater Treatment

Schwing Bioset Receives EPA Approval

Schwing Bioset's "Bioset" Process was approved by the Environmental Protection Agency (EPA) as a Process to Further Reduce Pathogens under certain conditions, which can be found in the attached document.

Tags: Class 'A' Biosolids, Bioset Process, Class 'A' Materials, EPA, Wastewater Treatment

SBI Installs New Beneficial Reuse Bioset System in Northern Minn.


Schwing Bioset Announces New Beneficial Reuse Bioset System Installation in Northern Minnesota

The Bioset System will enable the Coleraine/Bovey/Taconite Joint Wastewater Commission to produce a soil amendment that meets the USEPA Class 'A' standards year round

Itasca County, MN- In Q3 of 2009 Schwing Bioset was awarded the contract to provide a Bioset System to the Coleraine/Bovey/Taconite Joint Wastewater Commission. This system was the lowest cost when compared to other technologies, and it produces a USEPA Class ‘A’ end product, unlike the other technologies that produced a USEPA Class ‘B’ material. The installation was completed in Q2 of 2011 and is fully operational.

The existing digesters could not meet the USEPA Class B standards in the winter months so the Commission needed to find a solution. After a reasonable amount of due diligence, the Commission secured the services of a local consulting engineering firm to explore alternatives for meeting the USEPA standards year round.

The engineer was faced with several challenges as they began their investigation. The plant was small, processing 0.5 MGD, and most available technologies would not scale down well or work well with intermittent biosolids processing. Another challenge was related to protracted winters and the need to find a place to store Class ‘B’ materials until the ground thawed and the biosolids could be land applied on the Commissions’ hay fields.

After considering options of a new digester, retrofitting the existing digester with heat exchangers, and reed beds, ultimately the Bioset process, Schwing Bioset’s alkaline stabilization process, was selected as the best available technology to meet these challenges.

About Schwing Bioset

For more than 25 years, Schwing Bioset has been helping wastewater treatment plants, mines and power generation customers by engineering material handling solutions. Schwing Bioset’s custom engineered solutions can be found in hundreds of wastewater treatment plants in North America as well as mines and tunnels around the world.



Tags: Biosolids Processing, Bioset Process, Alkaline Stabilization, Class 'A' Materials, Biosolids, Wastewater Treatment

Field Storage of Biosolids

Now that you’ve implemented your process (perhaps the Bioset Process?) for turning sludge into Class A biosolids, you’re probably faced with a new concern: what to do with all this high-quality fertilizer? If you’re providing it to farmers or citizens for land application, it might go out fast enough during some seasons of the year, but municipalities are generating wastewater year-round, even if the ground is frozen or fallow. The EPA provides guidelines for biosolid storage. Some of the primary concerns are:

  • Site Selection Considerations
  • Field Storage: Stockpiles
  • Field Storage: Constructed Facilities
  • Odor Prevention and Mitigation
  • Spill Prevention and Response
For site selection, you’ll want to consider some key factors:
  • Climate: How will weather affect the location? Do the prevailing winds blow odor toward a community? In many areas of the United States, land application of biosolids is severely limited from November through March.
  • Topography: Is the location regularly inundated by water or in a wetlands? Is it fairly level? Stockpiles should be near the top of slopes to minimize exposure to up-slope runoff. Storm water controls may be necessary. Storage locations should be in areas with adequate buffers.
  • Soil/Geology: Sites should not be located on excessively moist or wetland soils that regularly have standing water or excessive runoff after storms, or areas with loose soils (gravel or sand) that permit excessive infiltration.
  • Buffer Zones: Sites must comply with any federal (10 meters by the 503 rule), state, or local regulations regarding minimum buffer distances to waterways, homes, wells, property lines, roads, etc.
  • Odor Prevention/Aesthetics: Try to minimize visual and odor impact on residential areas. Storage during the summer poses a greater potential for development of unacceptable odors and requires a higher level of management.
  • Accessibility and Hauling Distance: How far do you have to haul sludge and/or biosolids? What’s the accessibility of the site during bad weather, or heavy traffic? Take note of weight restriction and other roadway limits along the haul route. Consider the traffic impact as well.
  • Property Issues: Ensure local zoning requirements and ordinances are met, and consider the relative security and liability associated with leasing versus ownership of the land. Any leases should extend for several years and preferably over the expected life of the facility.

Schwing Bioset’s advanced processing technology can help you understand and meet these requirements. To learn more, contact Schwing Bioset.

revinu fertilizer

Tags: Class 'A' Biosolids, Bioset Process, Biosolids, Wastewater Treatment, Fertilizer

Feeling Green: Biosolids 101

Can you imagine living in a world where all of our raw sewage is dumped directly into rivers, lakes, or bays? What would that mean for your next fishing trip, your next family vacation to the ocean, or your next hot summer day spent splashing around in the local lake or creek?

Many of us don’t need to use much imagination to picture this scenario, because it wasn’t so very long ago that this careless sewage dumping happened in thousands of cities across America. According to the EPA, it was just thirty years ago that sewage made a one-way, non-stop trip to the water surrounding us.

My, how far we’ve come.

Today, thanks to vast improvements in wastewater treatment processes, American waterways are no longer the dumping grounds that they once were. Advanced wastewater treatment makes our waterways more hospitable to swimmers (both human and aquatic), and it also produces one very green side effect: biosolids.

As defined by the EPA, biosolids are “the nutrient-rich organic materials resulting from the treatment of sewage sludge.”

Sewage sludge isn’t very useful on its own, but once it is turned into biosolids, its potential is nothing short of extraordinary. Biosolids can be recycled and turned into super-powered fertilizer, which can be applied to land used for growing food. Today, roughly half of biosolids produced in the United States are being applied to land to beneficially improve soils. That’s a lot of recycled waste!

The EPA uses strict criteria and guidelines to ensure that biosolids are used safely. Thanks to these regulations and reliable, efficient biosolid processing systems like the Schwing Bioset process, raw sewage can be part of the ever-increasing green movement. Who knew poo could be as trendy as a canvas grocery bag?

canvas grocery bag

Tags: Biosolids, Wastewater Treatment, Schwing Bioset Process, Fertilizer, Recycled Waste

The Biosolid Journey

Somewhere, perhaps not far from where you are, biosolids are enriching soil and improving the land. Much of the biosolids produced in the United States are used to beneficially improve farmland, and biosolid application isn’t necessarily limited to agricultural use. Biosolids meeting the EPA’s criteria can be beneficially applied to forest land, reclamation sites, golf courses, public parks, roadsides, plant nurseries, and, in some cases, lawns and home gardens.

So biosolids can end up just about anywhere—but how do they get there? Biosolids result from the treatment and processing of sewage sludge. Biosolid processing can be a relatively simple process, especially when the right treatment system is put to work. Schwing Bioset has the treatment process down to a science, and many wastewater treatment plants prefer the Bioset process for its ease of operation, lack of dust and odor, minimal maintenance requirements, and low cost.

Systems like the Bioset process are able to turn sewage sludge into biosolids that meet the EPA’s criteria for ‘Class A’ biosolids. Class A biosolids are safe for land application—even land that is used to grow food. Once the biosolids have been treated and processed, they are ready to be put to use, enriching soil with necessary nutrients.

Sometimes biosolids are sprayed onto soil surfaces, and they can be tilled or injected into the land. In a liquid state, biosolids can be applied using tractors, tank wagons, irrigation systems, or special application vehicles. As a matter of fact, biosolid land application doesn’t differ too much from the application of limestone, animal manure or commercial fertilizers (but thanks to the treatment from systems like the Bioset process, biosolids don’t smell like animal manure!).

biosolid fertilizer

All across America, soil is being conditioned and fertilized by biosolids that began as sewage sludge.

What does your town do with its sewage?

Tags: Class 'A' Biosolids, Wastewater Treatment, Schwing Bioset Process, Fertilizer, Sewage Sludge

Biosolid Land Application Requirements

biosolids1EPA Part 503rule lists four options for meeting pollutant, pathogen, and vector limits in biosolids that are applied to land:
  • Exceptional Quality (EQ)
  • Pollutant Concentration (PC)
  • Cumulative Pollutant Loading rate (CPLR)
  • Annual Pollutant Loading Rate (APLR)

Each option is equally protective of the public health and the environment, so EQ, PC, CPLR, and APLR biosolids used in accordance with the Part 503 rule are all equally safe. For a detailed discussion on these four options, the best bet is to refer to the EPA, but the table below gives a brief primer on each.


Pollutant Limits

Pathogen Requirements

Vector Attraction Reduction Requirements

Exceptional Quality (EQ) Biosolids

Bulk or bagged biosolids meet pollutant concentration limits

Any one of the Class A requirements listed here

Any one of options 1–8 listed here.

Pollutant Concentration (PC) Biosolids

Bulk biosolids meet pollutant concentration limits

Any one of the Class B requirements listed here

Any one of the ten options listed here.

Any one of the Class A requirements listed here

Option 9 or 10 listed here.

Cumulative Pollutant Loading rate (CPLR) Biosolids

Bulk biosolids applied subject to cumulative pollutant loading rate limits listed here

Any one of the Class A or Class B requirements listed here

Any one of the ten options listed here.

Annual Pollutant Loading Rate (APLR) Biosolids

Bagged biosolids applied subject to annual pollutant loading rate limits

Any one of the Class A requirements listed here

Any one of options 1–8 listed here.

* Each of these options requires that the biosolids meet ceiling concentrations for pollutants, monitoring requirements, and recordkeeping and reporting requirements. See the EPA’s Part 503 Rule, Chapter 2 [PDF] for more information.

Schwing Bioset’s advanced processing technology can help you understand and meet these requirements. To learn more, contact Schwing Bioset.

Tags: Biosolids, Wastewater Treatment