News from Schwing Bioset

Biosolids, Their Benefits, and Schwing Bioset Solutions


Written by Kelly Kramer


Sewage Sludge vs. Biosolids in Plain English

The terms ‘biosolids’ and ‘sewage sludge’ are often used interchangeably, but they are certainly not one in the same. 

Sewage sludge refers to the bodily waste we produce every day and the solids that are separated during the treatment of municipal wastewater generated in a treatment works. Sewage sludge is the raw material used to create biosolids, but at the wastewater treatment plant, those solids are then treated physically and chemically to produce a semisolid product known as biosolids.

Class A Biosolids

Biosolids are nutrient-rich organic materials, and through biosolids management, solid residue from wastewater treatment is processed to reduce or eliminate pathogens and minimize odors, forming a safe, beneficial agricultural product.

By the time they are applied to land, the waste has been treated and turned into a safe alternative to chemical fertilizer, now resembling a material more like soil. Biosolids are treated to meet standards set by EPA and state regulators and are regularly monitored.

The EPA categorizes biosolids as Class A EQ (Exceptional Quality), Class A/AA, and Class B. The difference between these types depends on the quality of the material and the distinction helps ensure safe use.

Class A EQ are the highest quality of biosolids and are approved for use in gardens that grow food. Class A biosolids are the next highest-level quality, can be applied to land safely with no restrictions, and are commonly used as compost or fertilizer. Class B biosolids are lower quality than Class A, but are still approved as a compost or soil improvement for farmland with permits and regular monitoring. For more specific information on Class A vs. Class B, take a look our previous blog post.

Biosolids are one of the most researched soil amendments on the market. Utilities, trade associations, and regulators are continually researching the benefits and effects of using biosolids.  


Benefits of Biosolids

Biosolids are a natural and endlessly renewable resource. Using biosolids reduces waste, recovers natural resources, generates renewable energy, lowers greenhouse gases, and improves the quality and health of soil.

Just some of the benefits that Biosolids provide include:

  • They are a natural and renewable resource and are loaded with nutrients that are better for the environment, including waterways, than chemical fertilizers.

  • Biosolids do more than just replace nutrients, they actually improve the health of the soil and allow for the slow release of key compounds like nitrogen and phosphorous. They help increase crop yields, boost plant growth, and promote rapid tree growth.

  • The production and use of biosolids reduces waste, reduces the production and need of chemical fertilizers, and beneficial reuse helps keep them out of landfills and incinerators.
  • Using biosolids lowers greenhouse gas emissions. Use on farms helps soil store carbon, which reduces greenhouse gases by keeping it out of the air.
  • Biosolids help create resilient local economies, and farmers save money by using biosolids because they are less expensive than chemical fertilizers.
  • Biosolids are an alternative to chemical fertilizers for healthy farm soils, community gardens, golf courses, and municipal parks, to name a few.
  • The production of biosolids allows utilities to create a natural fuel that can be used for heat and power. Using energy from biosolids helps with electricity demand.

Class A Biosolids


How Can Schwing Bioset Help Your Wastewater Treatment / Water Reclamation Plant?

Schwing Bioset is your complete biosolids management provider, helping hundreds of wastewater treatment plants around the world with our custom engineered solutions. We produce equipment that can treat, dewater, transport, and store biosolids.

Bioset Process (Treat)

The Bioset Process uses Alkaline Stabilization that produces Class A, Class AA, or Class AA/EQ Biosolids via the time vs. temperature equation and pH adjustment per the EPA 503 regulations. Temperature is achieved through the addition of sulfamic acid and high pH is achieved through the addition of quicklime. Biosolids and the additions are homogeneously mixed in a Schwing Bioset screw feeder and pumped through an insulated reactor.

Fluid Bed Dryers (Treat)

Fluid Bed Drying is our indirect-heated, thermal drying technology for producing Class A material from dewatered municipal wastewater treatment sludge. Based on the use of a fluidized bed dryer, the approach is to granulate and heat the biosolids within the dryer, and produce a dry, cool, dust-free material as the end-product.

Screw Presses (Dewater)

The Schwing Bioset screw press provides a state-of-the-art solution for wastewater plants and consulting engineers looking to improve their dewatering process. The Screw Press offers next generation dewatering for those wanting a cost effective, durable, efficient unit to reduce the volume of their biosolids. Dewatering results are similar to high-speed centrifuges, but with a fraction of the energy and maintenance costs.

Piston Pumps (Transport)

A broad range of Schwing Bioset pump systems with pumping rates exceeding 1000 gpm and pumping pressures over 3,500 psi on some models provide numerous possibilities for conveyance of materials previously considered un-pumpable. Our units pump sludge and dewatered biosolids from Belt Presses, Centrifuges, Plate and Frame Presses, and Rotary Presses with dry solids content up to 56%. 

Conveyors (Transport)

Screw conveyors are an efficient solution to collect, classify, transport, and distribute materials, or unload silos. Designed for use in demanding applications and to move a wide range of materials, the high-quality conveyors Schwing Bioset produces are available in multiple configurations to suit the challenges of every application.

Sliding Frames & Storage Silos (Store)

Sliding frame and push floor storage silos provide a low-cost method to store both large and small quantities of biosolids while awaiting final disposal. Silos can be used for intermediate storage, truck loading, or accepting foreign sludge hauled in from other plants as a truck receiving station.

Paragould AR_cropped 

To learn more about how we can help solve your plant’s challenges with Biosolids Management, visit our website or contact one of our Regional Managers.


References used in this post, and resources where you can find much more information, include:

Water Environment Federation (WEF)

A Plain English Guide to the EPA Part 503 Biosolids Rule

North East Biosolids and Residuals Association (NEBRA)


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Tags: Class 'A' Biosolids, Municipal Biosolids, Class AA/EQ Biosolids, Biosolids, Biosolids Management

Schwing Bioset, Inc. Expands its Leadership Position as the Class A/AA Biosolids Solution Provider


Published on April 14, 2015 (Somerset, WI)

Schwing Bioset, Inc. has completed another successful Beneficial Reuse installation.  The City of Immokalee, Florida, chose Schwing Bioset to provide not only its Best in Class equipment, but design and build capabilities as well.

The heart of the system is the patented Bioset process and reactor that converts raw sludge into Class AA Biosolids, making it ready for easy land application.  Licensed as a fertilizer in the state of Florida, the Class AA product produced by the Bioset process is a highly marketable and sought after product.  Millions of tons have been produced and beneficially reused by the Bioset process. 

Taking advantage of some of the other high quality products Schwing Bioset offers, Immokalee integrated their Twin Piston Pump and Dewatering Screw Press into their design.

The Immokalee Water & Sewer District Executive Director, Eva Deyo, is very pleased with the system.  “The project came in under budget and went from concept to completion much quicker than other options.  As promised, the Schwing Bioset solution has proven to be easy to operate for our staff and very cost effective to operate, and the end product is exceptional,” said Deyo.  

Schwing Bioset Regional Sales Manager, Tom Welch, is thrilled with the results of the project.  “The City of Immokalee was tremendous to work with throughout the entire process.  Their vision and understanding of the value that the Schwing Bioset solution offered was evident throughout.  They realized after investigating numerous options that you don’t have to break the bank to get state-of-the-art technology,” said Welch.

“The experience of our Design, Engineering, and Project Management Teams has really shown during the execution of this fast track project.  The Schwing Bioset Team has executed on well over $150M in projects, with 2015 proving to be our biggest year ever,” said Tom Anderson, Owner and President of Schwing Bioset.

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.

For questions or more information, please contact Schwing Bioset at 715-247-3433 or, or visit the website at

SBI Logo Small resized 600

Tags: Bioset Process, Piston Pumps, Municipal Biosolids, Beneficial Reuse, Class 'AA' Biosolids, Biosolids, Wastewater Treatment, Fertilizer, Recycled Waste, Schwing Bioset, Municipal, Screw Press

USEPA PEC Committee Grants PFRP Approval to the Bioset System

The USEPA PEC Committee Grants Nationwide PFRP Approval to Schwing Bioset and Its Class 'A' Biosolids Process known as the Bioset System

After extensive testing and research, Schwing Bioset is proud to announce that the USEPA has given nationwide approval to the Bioset Process to reduce its operating temperatures from 70°C (158°F) to 55°C (131°F) as a Process to Further Reduce Pathogens (PFRP). Operating at 55°C (131°F) results in a greater than 20% reduction in operating costs for owners of the Bioset process.

Somerset, WI 2011

After extensive testing and research, Schwing Bioset is proud to announce that the USEPA has given nationwide approval to the Bioset Process to reduce its operating temperatures from 70°C (158°F) to 55°C (131°F) as a Process to Further Reduce Pathogens (PFRP). Operating at 55°C (131°F) results in a greater than 20% reduction in operating costs for owners of the Bioset process. Prior to receiving nationwide approval, site-specific approval at one site in Texas had been granted.

The Schwing Bioset Process is a technology that continuously converts municipal biosolids into a Class A/EQ saleable product in full compliance with 40 CFR Part 503 Rule. The process mixes dewatered biosolids with calcium oxide (quicklime) and sulfamic acid (solid granular acid) and continuously pumps it into a plug flow reactor. The Schwing Bioset Process currently meets Class ‘A’ standards via pasteurization at 70°C for 30 minutes, and vector attraction reduction by maintaining an elevated pH.

At the elevated pH levels, ammonium contained within the biosolids evolves as ammonia, and the ammonia is maintained in solution with the biosolids in the pressurized plug flow reactor. Miscible contact of the ammonia with the biosolids enhances pathogen destruction to Class A/EQ standards at lower temperatures. Mixing is accomplished with Schwing Bioset’s twin-screw feeder and the blended material is pumped into the plug flow reactor with Schwing Bioset’s twin- cylinder positive displacement piston pump.

The combination of high temperature, high pH and the biocidal effects of ammonia ensure that the biosolids are pathogen free in accordance with Class A/EQ requirements. The end product is characterized as a lime enhanced soil amendment and is a valuable product for numerous land application markets. Because the Calcium in the Class A/EQ end product is readily available, soil pH adjustment occurs in less than half the time of what typical agricultural lime products require. An additional benefit of the end product is that the high percentage of organic content (35-55%) returns organic material to depleted soils.


Tags: Class 'A' Biosolids, Piston Pumps, Bioset System, Municipal Biosolids, Class 'A' Materials, Screw Feeders, Biosolids