top of page

PFAS & Biosolids: A Community Success Story

In 2017, the Northern Wisconsin community of Marinette received unexpected and shocking news. An industrial discharger notified the Wisconsin Department of Natural Resources (WI DNR) that firefighting foam leached offsite and was in the groundwater. The words "PFAS" were muttered and looks of confusion spread across the faces of the wastewater team. "What is PFAS and why is this a concern?" Little did the Marinette team know, their future of their daily operations would quickly change.

Warren Howard, Marinette Utility Operations Manager, was asked to share the facilities story of addressing PFAS contamination at the Michigan Water Environment Association's 2023 Spring Conference. Along with the Marinette wastewater team members, Paul Nygaard from the ICS Group joined the team to present the obstacles with PFAS, the process of targeted collection system sampling, sealing contaminated connections, addressing the stored contaminated biosolids, and upgrading the facility to efficiently process sludge.


Warren Howard - We are here to talk about our PFAS issue at Marinette. First off, we do have a responsible party, which manufactures firefighting foam and fire extinguishers. We have been dealing with this issue since 2017 and we will talk about that our story today.

We want to provide a quick overview of plant, our history, the description of the project, finding a solution, the project goals, solution, current state of the plant, and looking forward to the future. I’ve been at the wastewater plant a long time and I know there is a lot of wastewater operators here today. As operators, you really must get involved in process and as the older people retire and young people take over, they have to take the next step for the facility. Personally, I wanted to leave this position with something that would work for the team and the community.

First, we will start with an overview of our wastewater facility. Here is an aerial picture of our plant. The average flow is 2 MGD. We use ferric chloride for phosphorous removal. We are a conventional activated sludge plant, pretty simple. We also have dissolved oxygen control and ultraviolet disinfection systems. So, this is a basic wastewater treatment plant design. We intentionally over-designed when we upgraded the plant. We can handle up to 16 MGD, but we are currently doing 2 MGD. We have redundancy which is good. Here is a storage tank for a facility our size and the two digestors to the left of that (see above picture.) That was our life and that is how we handled biosolids.

We never thickened sludge and it was really simple with digestors. You just pump to the digestor, keep the temperature up, put the sludge in a storage tank, and then put it on the farmer's field. We used to have a DAF tank years ago before we upgraded in 1991. The DAF was a hassle, so we got rid of it and where the DAF was located, that is where we put this new process equipment.

Currently, we do about 12,000 to 15,000 GPD of sludge at 2-3% solids. In 2019, we had 3.5 million gallons of contaminated biosolids, and we do around 500 dry tons a year. We started land applying when we stopped incinerating biosolids back in the late 1980's. Traditionally, our facility approached farmers for land application. Spreading biosolids was simple. We would land apply twice a year and eventually shifted to just land applying in the Fall because we had so much storage and we could decant efficiently.

Life was good. Things were going well at the wastewater plant, we had new staff coming in, and then the mayor called me in November 2017.

The mayor said "The DNR wants to have a meeting with us today." Now, when EGLE or the Wisconsin DNR calls and says they want to have a meeting with the mayor - that is probably not a meeting you are going to be looking forward to. We had no idea what this meeting was about. I met the mayor ten minutes before the DNR was supposed to arrive and the DNR is already there. I’ve been in this business for 44 years and I know most of the DNR folks and these are some folks that are at a pretty high level for our meeting. Then we noticed a local industrial discharger showing up for the meeting too. I knew it was them because I was doing their pretreatment for years. I wrote their discharge permit to our plant.

The mayor asked, “What do you think they want? They are already here.” I said, “Well, I don’t think this is a big deal – but we will see.” We entered the meeting, and we sit down. The DNR starts explaining to us, “The company has just informed us that they have some aqueous film forming foam (AFFF) that has gotten offsite, has gone into the groundwater, and we want to let you know about this before it becomes public."

The first thing I thought is the public is going to ask, "What is PFAS?" Because I was a utility manager for all these years and said to myself, "What the heck is PFAS?"

The DNR and representatives from the industrial company left the meeting and the mayor said, “We have to get down there (the contamination site) and start sampling the water. We have to sample the drinking water and the groundwater. We have to test the private wells in town and the wastewater treatment plant.” Now, if anyone in this room was involved in the mercury initiatives for the Great Lakes, I was on that board. The talk of PFAS brought back memories of that time. I asked the mayor, “Are you sure you want to start sampling all that stuff, because you know what you are going to find, right? They already told you it’s there. And there is no regulation in place for us. What are we going to do with it?”

The mayor said, “We have to do the right thing.”

And I think it was the right thing too. After the meeting, I went back to the plant and that’s when I reached out to my team to get them involved. I informed the team that we had a meeting with the DNR and the responsible party, and they want to sample our drinking water. At first, I thought that was strange because he wanted us to sample water near at the new recreation center right by the responsible party. They wanted us to sample by the high school, which is right by the responsible party's facility. I went to the team and said, "Here is what we are going to do so just tell me how we are going to get it done." The team selected the sampling methods for the drinking water at those specific sources and the influent/effluent.

Then the story begins.


Gabe Aschbacher, pretreatment coordinator at the Marinette Wastewater Facility, describes the discussion with Warren after the meeting with the Marinette mayor, DNR, and the responsible party.

Thank you. Like Warren said my name is Gabe Aschbacher. I am in charge of the industrial pretreatment program, assist with general operations at the plant, and I am also our lab technician. After the meeting with the DNR, the mayor directed Warren and our team to sample drinking water and wastewater. This sampling started in 2018. First, we sampled the community drinking water at the discharge point of the water treatment plant, as well as the new recreation center in Marinette. We sampled the drinking water around the high school to ensure that the educational centers were covered. Those samples all came back sub 10 parts per trillion. But when you get to wastewater, we found 38.2 parts per trillion of PFOA and 42.8 parts per trillion of PFOS.

In 2018, all we had to go off of was the EPA’s Health Advisory Levels (HALs) for PFAS which was 70 parts per trillion combined for drinking water, so we didn’t think it was that big of an issue. We took another sample at the mayor's request six months later. The mayor really wanted to understand the significance of transporting and land-applying the contaminated biosolids on farm fields.

We took a biosolids sample in May of 2018. We found 210 parts per billion of PFOS and 10 parts per billion of PFOA.

At the same time, we took another sample of the influent and effluent wastewater. The PFOA was 38.2 parts per trillion in November, but now it was 50.3 parts per trillion. PFOS went down to 13.3 parts per trillion and we thought that was possibly due to dilutional flow from influent filtration from the Spring thaw or Spring rains. The sampling showed that the PFOA levels were the same and the PFOS levels had gone down.

In September of 2018, we shared our May results of our biosolids sampling with the Wisconsin DNR. At that time, the DNR formally requested us to halt biosolids land application until they could further review PFOS across Wisconsin, how they wanted to move forward, and figuring out their strategy for industrially impacted biosolids. Luckily, as Warren pointed out earlier, we have a 4 million gallon holding tank for our stored biosolids. At that time, we were in no hurry to get rid of any biosolids. We told the DNR, "We will give you guys more time to review. But, with the understanding that around November of 2019, that is when we are going to run out of storage room."

Finally, in March of 2019, the DNR came back and advised, “We are requesting you halt all land application and research landfilling or incinerating all of your biosolids." At this time, we had about six months of capacity left in our storage tank. Think of it, three million gallons of 5% solid sludge. Obviously, we knew it was 'hot' with 220 combined parts per billion of PFOA and PFOS. The potential impacts were quite great. We had a choice to make - landfill or incinerate? We used to get rid of our sludge at about 4.5 cents per gallon. Landfilling and incineration comes with additional fees and expenses skyrocket. We had to choose one or the other.

Transporting the PFOS compounds was also a concern. The Department of Defense (DoD) is pretty leery of incinerating any PFOS impacted biosolids or anything else. All these variables really left us with choices on picking the appropriate avenue to move forward. Basically, we can’t haul 5% liquid at a rate of 3 million gallons over a year. Or every two years even and make it cost effective for our ratepayers.

We worked with the responsibly party to find a solution with what we do with our 3.5 million gallons of biosolids.

The responsible parties AFFF testing procedure had been going on since around the 1960's. The facility would let the AFF discharge to the ground and the DNR and everyone was okay with it at the time. Around the 1970’s or 1980’s, the responsible party requested that our wastewater treatment plant take a regulated volume of their foamy wastewater from the research and development laboratories. We accepted that waste and continued accepting that waste until March of 2019. With the new light on PFOS, our team initiated a sampling process. We had three industrial users in town who were known to work with AFFF.

We didn’t just want to hand-pick the industrial dischargers and say, “We’re going to sample you and say it’s your fault”.

We wanted to do our due diligence. We conducted some targeted collection system sampling by dividing our collection system up into five quadrants and basically followed the PFOS contamination. After taking grab samples, we found where the PFOS sampled at elevated levels, and we definitely knew where the major players were. These dischargers were permanent industries with our pretreatment program, and we thought it was a good idea to sample their discharge from outfalls to the sanitary sewer collection system. The highest numbers we saw were 3,670 parts per trillion of PFOS from one of the outfalls at the facility where they do the AFFF research and development. Our team continued monitoring industrial dischargers and went through a large, lengthy process from 2018 to current of source reduction and the DNR helped us with this process.

The Wisconsin DNR promulgated rules regarding foam testing and treatment.

The AFFF research and development facilities, along with their team of engineers, brainstormed the best available PFOS treatment technologies. What they settled on was an organics treatment, moving on to carbon treatment, cloth filtering carbon treatment, and finally ion exchange. The responsible party constructed a 20-million-dollar facility so they can discharge their water at a non-detect PFOS levels to the wastewater treatment plant. We can't say enough, the responsible party has been great to work with.

There is some legacy PFOS contamination in town. We have been working on sealing different sewers and aging infrastructure.

Source reduction was a big initiative. We had one company in Marinette that wasn’t discharging any industrial waste but elected to seal their aging infrastructure and take all their process wastewater offsite to be safe. This company sealed their connection to the sewer because they didn’t want the liability moving forward. The PFOS plume in Marinette is probably 10 square miles. Some portions of that are upwards of 30,000 to excess of 100,000 parts per trillion just sitting in the groundwater table. We are worried about that up-flowing into any leaking pipes in the area.

Currently as of February 2023, we’ve reduced the PFOS to 6.2 parts per billion 1.6 parts per billion of PFOA through source reduction. Source reduction works.

You may be asking, "What did we do with the 3.5 million gallons of contaminated sludge?" How are we going to handle these contaminated biosolids? The state of Wisconsin is still sitting on interim standards with the DNR with no promises of a final standard. We looked at landfill vs. incineration. Incinerators had some uncertainty with the transportation and if the PFOS goes into the air, besides the cost of transporting the contaminated biosolids to Kentucky or Canada for incineration. You need to add up all those expenses and plus you have to pay for the final incineration. Landfilling was ultimately cheaper. We worked with Waste Management to identify one landfill that would take our PFOS contaminated biosolids. So, we made the best decision we could.

We were running out of storage.

We had six months of storage left and we were decanting the clean water off the top aggressively. Ultimately, we had a 4-million-gallon tank that had 3-million-gallons of sludge in it that wasn’t going down. Our team worked with Arcadis, WI DNR, Waste Management, our local contractor, FSO, and Clean Harbors to develop a solution. In the beginning of the process, we belt pressed all those biosolids to about 18% and the contaminated biosolids went into lined and sealed Waste Management 10-yard boxes. Then they were trucked to Chicago. After they arrived in Chicago, they were then sent by rail to Oregon where the Columbia Ridge landfill is located. They’ve got a combined hazardous waste and regular municipal waste landfill. The leachate from the regular landfill goes to hazardous waste landfill, so we felt comfortable with this facility. The PFOS would be trapped and stored there.

One thing the Wisconsin DNR was concerned about was the side-stream coming back to the plant. They elected us to go with filtrate PFAS treatment. We collected all the filtrate from the belt press and settled out any large particles to be dealt with again on the belt press. The resulting water went through sand filtration, bag filtration, GAC filtration and then that was rerouted to the head of the plant on non-detect levels of PFOS. So, it was a pretty good system.

It took about three weeks to get rid of that 3.5-million-gallons at around $1 per gallon.

The responsible party picked up the bill of $3.5 million to get rid of 3.5 million gallons of biosolids. Up until February of 2023, we were still hauling our biosolids to Oregon. Through source reduction, we were able to drop the PFOS levels enough, so Waste Management felt comfortable with us changing our process. We are now hauling our biosolids via truck in two 30-yard containers to Manitowoc, Wisconsin to the Whitelaw landfill that will accept our levels of PFAS contaminated biosolids.


Marinette's Chief Operator, Andrew Vitek added his insight and perspective to the sludge hauling conversation.

After we saw the price tag of hauling sludge to Oregon, we decided we needed to have a new process. Our project goal was to reduce the volume of the sludge weight. When we started planning, we knew we didn’t want any new major construction and preferred to use the existing layout of the plant. The technology needed to be low maintenance and relatively simple to run, as well as energy efficient.

Our long-term solutions were to do the right thing for the environment and our rate payers.

We were looking for the best solution for our community and the surrounding communities because we had about 60 fields that received biosolids for land application. It was an ominous feeling, but we went to work, and Warren did quite a bit of homework. We looked at all the different technologies, we went to a bunch of conferences and talked to manufacturers to find the right solution.

Here are some items to consider when upgrading biosolids.

  • Our considerations for the equipment centered around using our existing infrastructure.

  • After we went through the process of landfilling the biosolids across the country, we understood that disposal costs were high, and we did not want to break the bank with construction.

  • With the responsible party upgrading their pretreatment and lining their site, we knew they would have cause to relinquish their title as the responsible party.

  • Through sampling, we knew our background concentrations would not allow us to return to land application until we got solid guidance from the DNR, which would take more time than we had to spare.

  • We had a 60 ft long by 20 ft wide building from a legacy process that was available, and we identified this space for the biosolids upgrade.

  • Looking at all the different technologies for dewatering and drying, the size of the equipment and our available space would be an issue.

Warren and Paul met at a conference, and he brought to our attention the PWTech press and the Shincci-USA dryer. We looked at the dimensions and we found that both systems would fit our footprint perfectly.

Moving forward, we scheduled a pilot for the PWTech press and experienced good results with pressing our primary solids. We tried to press our digested solids and found that it required more chemical costs, so that was not the answer. We ultimately decided we could decommission the old digestor system and we could save on all the operations and maintenance costs associated with digestion and storage. Right now, we just take primary and co-thicken with the secondary sludge and we press that sludge.

After the piloting, we sampled our pressed primary sludge for PFAS and we noticed the concentrations were a lot lower than the 200 ppb that we had seen. Because we weren’t decanting the sludge, it wasn't concentrating the contamination. When it came to the dryer, we were a little concerned with the maintenance and operation that comes with the process. We have a lean staff, three operators and two collections systems specialists that the work would ultimately fall on. Before we committed to the technology, we visited a dehumidifier installation in New Jersey. We flew out to the facility and walked through with their crew.

During the tour, we saw that the most complicated thing you would do with the machine was change out a bearing. After seeing that, we made our decision that it was the most cost-effective dryer for the space we had available.

Let's talk about installation and startup. The installation was a great experience for us young operators. Our first shipment came with significant cosmetic damage, so we ultimately rejected it, and Shincci-USA sent us a new one. This delay put us back about four months. Even though the equipment couldn't be installed immediately, it was a really cool opportunity because we actually got to disassemble all the internal components of that machine. When the new one arrived, we got to put all the components back in. We had a very intimate understanding of our technology.

The installation was unique in that Shincci-USA planned to send their representatives to oversee the construction, commission, as well as train us on the technology. This happened midway through COVID, and China was on lockdown, and we did not have our specialized training. We got a crash course on how to run the dryer. We had never operated a press or dryer, so we figured out all the ways not to run a press and a dryer. Initially we were a little frustrated, but now we have a good understanding of both systems. We know the technology inside and out as well as anyone can.

We’ve learned a lot over the last year and continue to keep learning. Currently, we decommissioned the digester and storage tank. Dewatering numbers: we will take 10,000 to 20,000 gallons of sludge at 2-6% solids and we will press it to 20-27% cake. We dry that cake to 85-95% solids in the dryer. We have run the PWTech and Shincci-USA system for a whole year without any complaints about odor from surrounding businesses and apartments.

Paul Nygaard, President of the ICS Group, provided some insight on air permits and odor control. "This is because the dryer operates at less than 80 degrees Celsius. At that temperature you are not volatilizing the odor producing compounds that would generate out of a typical dryer. When the DNR worked with us on the project, they did not require an air permit for it based on the technology and what it was doing. The only smell in the room is from the primary solids that are going through the press."

If you didn’t have the PFAS or concerns from the community, could you land apply this under Wisconsin rules of factor reduction?

Utility Operations Manager, Warren Howard commented on land application: "Here is the situation, there are a lot of lawsuits in Marinette right now. We know we can land apply biosolids right now because we are at 8 parts per trillion. Honestly, we follow Michigan’s standards because EGLE is ahead of us, and we follow recommendations they give us from groundwater to the biosolids. But we are just going to landfill it until all of these lawsuits are done."

"Contamination is on every one of those fields that originally accepted our biosolids. The farmers are obviously impacted. We could land apply because we are below the limits, but we just opting to take to a landfill. Hopefully, someday, we will see the lawsuits concluded. These are multi-million-dollar lawsuits. The responsible party alone, with the GAC system and everything they have done in the community has probably spent over a $100 million and they aren’t even close to getting done."

Andrew Vitek commented, "We are really trying to figure out the ethics of it. I know MPart (Michigan PFAS Action Response Team) is just getting into sampling the plants that grew in fields with biosolids application. They chop down the plant and they are working with the EPA to make a method to say what is going on with uptake. We are waiting on you (Michigan) to finish that science up."

Wastewater plants in the state of Wisconsin will be required to sample for PFAS through their WPDES permits. Still, Marinette is trying to do the right thing. At the end of the day, they don’t know what the right thing is because the state has not defined a number. Warren Howard stated, "We aren’t trying to influence other people to not spread biosolids, but we are going to fill up landfills. We can’t do that. We’ve got to find a PFAS number that gives us a limit and we will meet it. Even with PFAS in drinking water, is 20 parts per trillion good? Is four parts per trillion good? Zero is probably better, but we got to find a number that is going to make it work for us."

We appreciate Michigan and what they have been doing (with PFAS). We are just following your lead.

Can the PFAS in biosolids be destroyed? If so, what contaminants go into the air? Warren Howard mentioned, "We are going to pilot with a company to do the pyrolysis process and it’s been out there. We want to see if we can get involved in it. Right now, we are going to see where it all goes. We are trying to do what is best and in the long run we are trying not to get too ahead of ourselves. I know we are ambitious, but there is a point. So, putting the biosolids into a dumpster and hauling it is a heck of a lot easier. But we are working on it. I am trying to get a pyrolysis pilot in to see if we can make it work."


Paul Nygaard, President of the ICS Group, entered the conversation to discuss the biosolids upgrade technology.

"What my role was as a part of the team, these guys put trust in my organization, ICS Group. We are a manufacturers rep based out of Green Bay, Wisconsin. We cover the upper peninsula of Michigan, downstate Michigan, northern Illinois, and Wisconsin. We specialize in all process wastewater technologies. One of the things we really focus on is innovative, yet well proven technology. As these guys mentioned previously, we met at the WWOA conference. We talked in 2019 and then we ended up starting to work through this process, design, discussing challenges, and trying to figure out some of the key things they wanted:"

  • Small footprint.

  • Ease of operation.

  • Low maintenance requirements.

  • Low manpower requirement.

What I’m going to talk about is the major equipment components that we provided for the project.

"The entire process - from the mechanical equipment standpoint consisted of a grinder, progressive cavity liquid feed sludge pumps, polymer system, Volute Dewatering press, cake pump, followed by the sludge dehumidifier, and the conveying system. We are going to visually walk you through the plant, give you an idea of the start of the process to the end of what this looks like.

The first step of the process is we put in was a Muffin Monster Grinder, primarily because they had experiences with rocks in clarifiers and other debris that could be damaging to the progressive cavity pumps that we were using to feed the liquid sludge. We felt like this was a good step to protect those pumps. We have a lead-lag configuration with the progressive cavity feed pumps. They are alternating back and forth to spread the wear out between the two. The feed comes in from the right into the pump and to the left it goes up the stainless-steel piping. This equipment is in the basement of the old DAF building.

Then we go upstairs where we have our Velodyne Liquid Polymer make-down system that takes liquid concentrated polymer, making it down and feeding it directly in front of the press. Next is the PWTech Volute Dewatering Press. This is a fully self-contained process that is skid mounted. On the right hand side, you got your control panel. Right behind the control paneling, you got your rapid mix and flocculation step. The tubes feed the two screws on the press. This has built in redundancy. The Marinette plant max design is 21,000 GPD at 2.5% feed solids. Typically, they are running at 12,000-15,000 GPD on average, so they have extra capacity there. The nice thing about the PWTech is the built in redundancy. The Marinette team can do maintenance on one screw while the other screw is still functioning and operating. Ultimately, they should never have to take the PWTech Dewatering Press offline for any kind of maintenance.

I’m going to talk about the mechanics on the two major components to give you an idea of why they selected these technologies. The PWTech Volute Dewatering Press is a very interesting technology in that it is similar to a screw press, but it has some fairly significant differences. When you talk about a normal screw press, there will be a wedge-wire, slotted screen or something on the inside that is retaining the solids. On the surface of the screw, you are going to have a wiper or a brush to keep the faces clean. Those eventually wear out and you must take apart the entire system to do maintenance. The PWTech technology is based on a moving ring principle. These blue rings are free floating rings, and the red rings are fixed.

The rings move in a serpentine motion. That diameter of the blue ring is slightly smaller than the flight diameter. It rides up and down on that flight. When it’s moving, you can see those rings pulsing in and out of the fixed rings. This creates a self-cleaning motion, meaning the press does not require wipers or brushes. There is nothing internal to the machine that must be taken apart and broken down from a maintenance standpoint. It also gives us tight tolerances. We are getting 97-98% TSS capture so our filtrate water going back to the head of the plant is very clean. The Marinette team was looking for 'ease of maintenance with little manpower', and they found that in the PWTech Volute Dewatering Press.

This is what the inside of the screw looks like. You have your feed on the left. This is like a gravity zone on a belt filter press, where you have all the free water that flows off, so the flights are shallow-angled and spread apart. As we move up into the dewatering zone, we can see the screw flutes out a little bit. The flute creates the back pressure inside the system to allow the dewatering plug to form as the flights get tighter together and the inclination goes up. There is an adjustable backplate where the operators can control the cake solids. The Marinette team is dewatering a mix of primary and secondary solids straight out of the clarifiers. They are averaging 22-26% dewatered cake currently and this machine is highly efficient.

Maintenance on the PWTech press is simply eight bolts on the back of the motor plate. Unscrew the bolts and the motor pops off. The cartridges slide out on a set of rails and the new cartridges go on. Basically, in under four hours, you can rebuild the press and be up and running again for another 12,000- 15,000 hours. Again, the PWTech press features the ease of operation the Marinette team was looking for. The Volute Press is all stainless-steel construction, a well-built machine. Our largest presses are only running at 400 GPM and pulling around 14 HP, which means the team has a lower cost of operation and stretches the taxpayer dollars.

After the press, we have the progressive cavity cake pump. As you may remember, one of the challenges the team discussed was having a 23 ft wide x 65 ft long room. They wanted to get the entire process done in this footprint. Obviously, that is an enormous undertaking. Normally we would feed off of here through an inclined conveyor system, but we didn’t have the footprint to allow it because the length would have been too long. Knowing this, we engaged the manufacturer cake pump manufacturer, Seepex. The pump takes the cake, pumps it up through the 4" pipe, goes up to the ceiling straight over into the dryer (See picture above.) It is all a vertical configuration and this technology helped minimize our footprint.

Then we move into is the Shincci-USA Sludge Dehumidification System. This is essentially the biosolids drying technology. Shincci-USA is different in the sense that we are dehumidifying sludge. The technology was developed in China and they carry several patents, but the key patent is the heat pump. Even though this equipment is manufactured in China, we have 'Americanized' the systems. All of the parts and components are Allen Bradley or Siemens controls, SEW EURODRIVE, NORD gear drives, and Danfoss compressors. The majority of the major mechanical components on this system can be found anywhere in the United States.

The reason why we recommended Shincci-USA for this project is because of the features and benefits. It is literally a stainless-steel box that sits on housekeeping pad and the only ancillary equipment to the dryer is the condensing fans. If you have looked at other sludge dryers, you will notice a lot of ancillary equipment because they are running at higher temperatures (300 - 800 degrees Fahrenheit.) Once you get up to those temperatures, you will get into dust suppression, combustion, explosion-proofing, and cooling towers. This technology is running at 75 degrees Celsius, which is around 165 degrees Fahrenheit. When we talk about this, the 80-degree Celsius temperature is critical because that is when the volatilization of odors occurs. If we are running below the 80-degree temperature, we don't generate any dust, odor, or combustion. We also do not need cooling towers for the finished product. Dust suppression and odor suppression - all those ancillary components go away.

On the top of unit, is the slitter box. That is where the cake enters the Shincci-USA system. And the cake gets formed into this (see picture on right.) It forms it like spaghetti strands. Shincci features a mesh belt. The air is flows up through the belt and picks up moisture from the sludge. The round-form of the sludge is the best way to evaporate the water out of the sludge compared to a flat or layered sludge. Another benefit of the round shape is the extra surface area which allows the heat to get inside the center of the sludge.

Principle of the operation for the Shincci-USA Sludge Dehumidification System

The operators turn on the system and the normal start-up time is 70 minutes. After the system is heated, they can start feeding sludge. The heat pump kicks on, starts heating up the inside of the reactor. Warm air comes in through bottom at approximately 75 degrees Celsius and goes up through the bottom of the belt. The system picks up moisture and turns it from water to humidity. The temperature drops to about 65 degrees as it moves up through the second belt, ultimately dropping the temperature to about 55 degrees Celsius.

In a typical dryer system, you would have to evacuate that moist air out of the system and must reheat the air. It costs a lot of energy and money to do that. The Shincci-USA system recaptures the humid air, sends it back into the system through a condensing cycle through a series of onboard compressors. This is very similar to how your cooling system in your house works. The moisture is compressed, turns it back into condensate or the water that came out of the sludge, and the air goes back to the heat pump system and now we are only having to make up the delta in the temperature from 55 to 75 degrees. There are drains at the base of the unit on both sides. These drains take the condensed water and sends it back to the plant. Other than the solids, the condensate is the only thing that comes out of this equipment.

This is an electric dryer and when some people hear it is "electric," they freak out. This equipment is highly efficient. This technology is using somewhere between 0.8 to 1.2 kWh of electricity per gallon of water. Shincci-USA is anywhere from three to five times more efficient than any dryer that is currently on the market.

The sludge comes out of the back end of the unit to a short shaftless screw conveyor. That shaftless screw conveyor then drops into this vertical paddle scraper conveyor. The paddle scraper conveyor feeds into this shaftless screw conveyor, which goes into the load-out building. Total time in processing from the time the sludge hits the press to the time it leaves the dryer is about 4 hours. We can take them from 2.5% to 92% dry in about 4.5 hours.

Fully automated equipment is necessary.

Gabe Aschbacher expressed the team's interest in fully automated equipment for this biosolids upgrade.

One of the other major considerations we had was we wanted the equipment to be fully automated. Here is an overview of how the automation helps our team. Our team has a dumpster change out on Friday. We shut off the dryer at 7am and package up our dumpsters so the truck can bring it down to the landfill. While this is happening, the Shincci-USA system is off for that six-hour period that it takes them to offload. Around 1pm in the afternoon, we will start up the dryer, start the press at 2pm and leave the plant at 3pm.

The whole process will run for the next 5-7 days with minor adjustments in the polymer addition or different press set points; but more or less the solids range from 20 - 25% and we don't have to touch the dryer set points at all. An additional automated benefit is the system shuts itself off if we feed it too much sludge or if there is a sludge characteristic change. The Shincci-USA system will shut the press off but keep the dryer running to process the sludge. It will automatically start the press and as long as the sludge hasn't changed, and this makes it great for 24/7 operation. Our team doesn't have an online SCADA system, so this built-in feature is key.

We are averaging 92 to 93 % dryness on the system.

At the end of the day, the ICS Group's equipment met the requirements that were important items for the Marinette team, which included less maintenance and energy-usage, a small footprint with no civil site work. We want to thank the opportunity to work with the Marinette team. They were completely invested in the project which is a benefit to make the technology work. It wasn't a streamlined process and there was a learning curve for everyone involved in it because of the new technology. But everyone worked their way through it. We are pleased to say the system is running well and is self-sufficient.

Warren Howard commented, "Personally, I have a mechanical background. I needed to see one (a dryer) in operation. In the state of Wisconsin, there are 10-12 different types of dryers. Engineers pick dryers when you see the pros and cons of each one. I'm just saying this one will be all over the country in 10 years. Some of the older dryers are large and they are labor intensive. I wanted something simple for our team. When I do retire, I wanted to leave these guys with something they could work with. I recommend operators and engineers to go throughout the state and look at some of these dryers. Some of them are really complicated. The Shincci-USA system is pretty easy and after a year we can say 'so far it is doing what we wanted it to do.' Time will tell. We were sticking our necks out being innovators, and its been really good."

The Marinette facility is always open and welcomes tours. If you are interested in viewing the biosolids upgrade in person, please contact the ICS Group.

86 views0 comments


bottom of page