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Heavy-Duty Pumps “Take the Cake” at Detroit’s Massive WWTP


Schwing Bioset Application Report 7, Detroit, MN

Written by Larry Trojak, Trojak Communications

Version also published in WaterWorld Magazine


Much like a chain, the wastewater treatment process is made up of individual segments, each linked to the next, each vital to its overall effectiveness. No single facet of the process, nor any single piece of major equipment, is more important than another; if one fails, it all suffers. Occasionally though, one piece of equipment has such challenging demands placed upon it that when it proves itself - and continues to do so for years - it bears mention.

At the Detroit Wastewater Treatment Plant (WWTP), a pair of heavy-duty pumps is used to take high solids-content cake from the dewatering operation to either incineration or a truck loading area.  That, in itself, is not noteworthy.  The fact that it accomplishes this both by pushing cake, dewatered to well over 20% dry solids content more than 500 linear feet, and taking it up five stories, is.  Today those pumps, a pair of Schwing Bioset KSP 110V(HD)L’s, move better than 100 wet tons of dewatered material per hour, have improved the efficiency of the incineration and haul-off operations, and have proven a key part of the system.

 Schwing Bioset Detroit WWTP Solids Pump


The Motor City Treatment

The first thing that strikes visitors upon arrival at Detroit’s WWTP is its sheer size. Covering several city blocks, the plant is the largest single-site wastewater treatment facility in the United States, with a capability for processing approximately 845 million gallons per day (MGD) through secondary treatment. The facility has undergone a number of major expansions since it was first built in 1940. At that time, it served Detroit and 11 neighboring communities; today it handles wastewater from 35 per cent of the state’s total population - a service area that covers 946 square miles.

The most recent of the major upgrades took place in 2004 when, according to Kenneth Paylor, Detroit WWTP’s Senior Maintenance Foreman (Solids), modifications to solids processing were included in the overall plan.

“One of the biggest changes that impacted this area of the plant was the addition of a Central Offload Facility (COF).  Up to that time, dewatered cake was taken by conveyor to a lime pad that was used to support land application for the biosolids.  When that land use was discontinued, however, an alternative was needed.  The COF, essentially a truck loading area to transfer biosolids to area landfills for disposal, is now that  alternative


Dewater is Different

To process its huge volumes of sludge, Detroit’s WWTP relies upon 14 incinerators located in two separate solids buildings, identified as Complex 1 and Complex 2 (C1 and C2). Solids content before dewatering ranges from 1.2 to 7% - generally in the 4.5% range. Paylor says the plant’s dewatering effort also underwent major changes in the ‘04 upgrade.

“To upgrade the dewatering operation, a number of belt presses were totally replaced and centrifuges were added in ’04,” he says. “We now dewater sludge with ten centrifuges and 22 belt presses: ten in C1, twelve in C2. Material exiting the presses has a solids content of about 23-27%; out of the centrifuges it can be in the 27-32% range.”


The Need to COF

In an ideal world, all of Detroit’s dewatered sludge would be sent directly to incineration, making the need for alternative disposal efforts a moot point. But this is not a perfect world and, to best deal with situations that are occasionally out of the ordinary, the COF was included in the design.

“There are times when we might have an incinerator or two that are down for maintenance and material needs to be re-routed,” says Paylor. “Another example is if our incoming volumes rise quickly - as they can after a heavy rain - and we are exceeding what we can normally handle. There was no way to avoid it; we needed a way to get material from C1 to a point where it could be hauled off site for disposal.”

Such occurrences are more commonplace than one would suspect. Even given the large number of incinerators in use and the obvious preference to keep those units fed with material to minimize fuel costs, Paylor says roughly 40% of their cake still heads to the COF. “That is when the Schwing Bioset pumps come into play: getting the cake from the belt presses in C1 to the COF where it can be treated with lime for odor control and loaded into trucks.”

 Schwing Bioset Detroit WWTP Truck Loading


The Long Haul

Using pumps to move cake in wastewater treatment plants is hardly a new concept. Scores of plants throughout the country—and internationally as well—have seen the benefits pumping can provide over moving material by conveyor. Improved production, better efficiency, improvements in site cleanliness and reductions in odor are just some of the gains that can be made by pumping.

“To get material to the Schwing Bioset pumps, which are located in the lowest level of the facility, a belt conveyor first collects the cake from all ten belt presses in C1,” says Paylor. “That belt feeds a Schwing push floor, which, in turn, feeds the two KSP 110V(HD)L pumps.”

With a maximum operating pressure of 1,500 psi, cake is pumped in high-pressure piping out to the COF. Mind you, it’s a fairly decent distance out to there.”

That assessment would appear to be something of an understatement. According to Keith McWilliams, Detroit’s Plant Supervisor, the distance from the C1 pumps to the COF is in excess of 500 feet. “Material first has to go up five stories—that’s 60-70 feet alone,” he says. “Then it has to make its way over to the facility, so 500 linear feet is probably a conservative guess.”


The Best Approach

McWilliams says there are alternatives to pumping the cake such a long distance. One of those, he says, is pumping it over to C2 where it could be dropped onto belts and taken to the COF.

“While that’s feasible, it is much better to do it this way,” he says. “Once we’ve put the cake into the pump, we may as well take it as far as we can. There is no advantage to dropping it on a belt—in fact, it’s a whole lot messier—and the pumps have shown that they can more than stand up to the challenge.”

Both Paylor and McWilliams say that since installation, the Schwing Bioset pumps, some of the largest the company makes, have been solid performers. XL model pumps were selected for Detroit WWTP based on the anticipated challenges to be placed on the units. Those particular models feature heavy duty poppets which reduce material velocity through the poppet housing. Doing so can result in a variety of benefits including: a reduction in pressure drop through the valve housing, an increased filling efficiency of the pumping cylinders, and a reduction in wear on the poppet discs, seats and pumping rams.

“In the five years the pumps have been in place, we’ve had very few issues with them, and those we’ve had, have all been minor” says Paylor. “That’s outstanding, given what they’re asked to do for roughly 30 hours every week, year round. Providing a continuous flow rate in the 150 to 200gpm range and taking it that distance is really impressive.”


Ongoing Changes

As mentioned, Detroit WWTP has seen its share of changes over the years, and new approaches to dealing with the biosolids are always under consideration. 

“We even have contingency plans already in place to handle things before any of those major changes occur,“ says McWilliams. “We put in different access points, for example, where the Schwing Bioset pumps could feed the conveyors in C2. 

Regardless of the direction Detroit’s WWTP takes, both McWilliams and Paylor say they are confident the pair of Schwing Bioset pumps will figure into those plans.  “Whatever happens will most likely involve further movement of the cake, says Paylor.  “And, given what we’ve seen from the pumps so far, I’m sure they can meet that challenge. They’ve been real workhorses for us.”


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Tags: Piston Pumps, Dewatered Sludge Cake, Wastewater Treatment Plant

Diversity, Equipment Longevity are Key for New York Wastewater Plant


Schwing Bioset Application Report 15, Glens Falls, NY

Written by Larry Trojak, Trojak Communications

Version also published in TPO Magazine, August 2013

Dewatering at WWTP

While most wastewater treatment plants focus their efforts solely on the material collected from within their own municipality, some choose-often for economic reasons-to supplement that volume with outside waste. After a major expansion in the late 1980s, and an upgrade in the mid-1990s, the city of Glens Falls (NY) Wastewater Treatment Plant found itself in just such a situation and opened up its facility to non-system waste. Today, drawing from a wide range of sources, the plant accepts an equally broad range of materials including: grease trap waste, sanitary holding tank waste, septage, sewer cleaning debris and wastewater sludge-both liquid and cake-from off-site facilities. That product diversity, coupled with impressive long-term equipment performance, has helped the plant remain viable in serving the upstate New York city and surrounding areas.

Legacy Lives On

Located on the Hudson River about 45 minutes north of Albany, Glens Falls is a picturesque small city, home to just under 15,000 residents, and a thriving base for the medical device and medical services industries. The city was also the site of a huge pigment manufacturing facility that was shut down in the 1980s, but left a legacy of contaminated soil in its wake. Today, nearly three decades after its closing, wastewater from the site’s groundwater treatment and collection system is still being processed at the Glens Falls WWTP, according to Jason Vilander, the plant’s maintenance manager.

“That pigment plant was actually a driving force in an expansion that took place here in the mid-‘80s,” he said. “A lot of water is used in chemical and dye work—water that couldn’t simply be discharged to the river—so the plant was designed to accommodate that additional wastewater volume. That expansion allowed us to move to activated sludge treatment and prompted installation of a fluid bed incinerator. Unfortunately for us, the pigment plant shut down during the latter part of our expansion, leaving us with a good deal of extra capacity.”

Since that time, Glens Falls WWTP has had an ongoing contract to accept and treat water from the groundwater collection system from the pigment plant site.

Filling the Void

Needing to fill the excess capacity left by the pigment plant’s untimely closing, Glens Falls WWTP began to actively seek companies or organizations looking to outsource their wastewater and waste product treatment needs. To say those efforts were a success would be an understatement. Today, the plant serves a fairly localized geographic area, taking in material from the town of Queensbury (six of its seven districts), as well as the Village of South Glens Falls, including the business centerpiece, Moreau Industrial Park.

But, because they were aggressive in reaching out to businesses throughout the region, they now also count many of them as customers. 

“We’ve had success in some unlikely places,” says, Vilander. “Most of our liquid sludge, for example, comes out of Vermont. That includes some of the larger ski resorts as well as many of the treatment plants from other towns and villages—plants that don’t have drying beds or digesters or any other means to take product through the final steps needed for it to be safe for disposal. So we provide that last step for them.”

Volumes are also supplemented by outside cake haulers, including regional correctional facilities such as Comstock Prison and the Washington County (VT) jail.

“These facilities all have their own wastewater treatment systems, complete with belt presses, which allows them to generate a cake. But that’s as far as they can go with it. So, twice or three times a week, they send us five tons of cake in a single-axle dump truck, and dump it onto a pad. We then use a pay loader to load that cake into a receiving station where it is stored until we have the time and manpower to incinerate it,” he adds.

Three Decades of Sludge

The benefits gained by reaching out for additional material would be a moot point were Glens Falls unable to effectively incinerate what it collects. Vilander says the equipment in place in many parts of the facility has amazed him in both its capability and its longevity.

“A good case in point would be our sludge pumps,” he says. “We had a pair of Schwing KSP-5 sludge pumps that were installed during that first plant upgrade in the 1980s. Those pumps—which were among the first made by Schwing for this market—have been outstanding for us, given what they’re asked to do. They were replaced just a couple years ago after nearly three decades of pumping. And mind you, they were replaced not because of wear issues, but because our volumes had grown so much over the years that we needed to upsize.”

He adds that the pumps’ impressive performance is made even more so given the fact that one of the critical steps in their routine maintenance was often overlooked for being “too inconvenient.”

“I’ve always felt that keeping the water in a pump’s water box clean is second only to keeping the hydraulic fluid clean,” he says. “Unfortunately for us, in the prior expansion, a grate, which allowed personnel to walk around the belt presses, was installed right over the top of the pumps’ water boxes, making access difficult. As a result, the water was changed far too infrequently. I’m still amazed at how well those pumps worked—and how long they performed for us—even with that lapse in an important operating procedure.”

With This Ring

Schwing Bioset Sludge Piston Pump at WWTP

With the upsizing to a larger pair of sludge pumps (Schwing KSP-10s), Glens Falls has increased their pumping capability to deal with the growth in biosolids handling at the plant. The new pumps take cake that has been dewatered to about 24%-26% solids and route it for incineration where a 32-ton load of cake (an 18-wheeler full) can be reduced to 100 pounds of ash. Moving that high solids content says Vilander, is helped by the addition of a “slip ring,” or pipeline lubrication system, a feature that injects a thin film of water to reduce friction loss in the pipeline and lower pipeline operating pressures—in some cases by more than 50%.

“We work so hard to get all the water out, so it seems a bit contradictory to be putting some back in," he says. "But, because we’re running these slip rings at about 20-30% of their capacity and they come on for only a matter of seconds, we are adding no more than three gallons per hour. So the amount of water added is minimal and pales by comparison to the improvement in throughput and the fuel savings we achieve with the drier sludge cake,” stated Vilander.

Additional benefits provided by the newer pumps include a much greater degree of versatility. Because the pumps are PLC-controlled, Vilander and his crew are able to have them run in several different modes including: “pressure,” tracking” or “manual.” That means they now have the capability to automatically control the speed of the hopper screws and the pump itself.

“With the old pumps, we could adjust our pressures a bit to get the speed we needed, but we couldn’t get independent control of both components—the screws and the pump, says Vilander. "Now we can and it’s made a huge difference. Because the pumps run nice and slow—and quiet— I’m not even seeing the level of maintenance that I had with the old ones. I can see these outlasting even those previous workhorses,” said Vilander.

Grease is the Word

The ultimate destination for all the cake processed through Glens Falls is a fluid bed incinerator which 18’ 3” in diameter with a height of 44’ 9”. The unit is designed to maintain an effective operating temperature of 1500°F and uses the cake itself as the primary fuel source. According to Vilander, if the cake is dry enough, it will reach an autogenous state and burn without an additional fuel source.

“However, if it’s too wet, or does not have enough VOC in it, we have to add BTUs through an alternative heat source which, in the past, was fuel oil. While the new belt presses gave us a much drier cake, we still found ourselves having to rely upon the fuel oil and the costs associated with it. As part of an overall cost savings move, we installed a two part grease system consisting of a concentrator and a storage tank,” said Vilander.

Doing so not only dramatically reduced the operational costs at Glens Falls; it also gave area businesses a way to efficiently dispose of grease from their operations. Now, the septage haulers simply bring the grease to the plant, pay a disposal fee and it gets concentrated, thickened and burned.

“Occasionally we will get a load of grease with wastewater added to it which has to be treated differently. So it goes into our storage tank where it is mixed and pumped up to our belt presses, combined with the cake and moved—once again using the Schwing pumps—out to incineration. The grease, which was once a waste product, is now both a fuel source and a small revenue stream,” said Vilander.

Better in the Long Run

If it sounds as though Vilander is a proponent of piston-style pumps versus their progressive cavity (PC) counterparts, it’s because he is, and that feeling is based on experience he’s gained at Glens Falls.

“We had an emergency situation arise a while back in which the incinerator was down and we had to take some steps to effectively store the cake until it was back online. We stockpiled it onsite but then had to find a way to re-introduce it into the system when we were up and running. So we teamed up a conveyor and a PC pump as sort of a makeshift solution. That experience taught me that, while PC pumps are certainly a lot less expensive; they do not handle grit at all and, given what we went through then, won’t last nearly as long,” said Vilander. He adds that they’ve never done a study to determine the total life cycle ownership/operation cost of their piston pumps versus that PC unit, but says he wouldn’t be surprised at all to find it costs more to run the PC pump.

“Our piston-style pumps were more expensive up front but we know they will provide decades of good service. I think we’ve already proven that,” said Vilander.


To download the entire #15 application report for Glens Falls, NY, click here.

To learn more about Schwing Bioset, our products and engineering, or this project specifically, please call 715-247-3433, email, view our website, or find us on social media.

To view a version of this story published in TPO Magazine, click here.


Tags: Sludge Pumps, Piston Pumps, Wastewater Treatment, Pumps, Dewatered Sludge Cake

City of Stockton WWTP - Enduring Performance, Replacing a Legacy


Written by Joshua DiValentino, August 27, 2015


The City of Stockton wastewater treatment facility has seen its fair share of challenges in recent years. When financial resources were limited, the burden fell upon the operations/maintenance staff and the existing equipment to continue operations with aging infrastructure. At this point, the piston pumps supplied by Schwing Bioset, Inc. (SBI), located in the sludge dewatering building, had been in operation for over 20 years.


The pair of KSP 25 pumps moved dewatered sludge cake from the dewatering building out to the truck loading building, several hundred feet away. The two systems were the only means of transporting dewatered sludge cake for the 30 MGD facility. Regardless of the operational circumstances, with a resourceful operations/maintenance staff and the help of SBI technical support, the pumps remained in service with over 129,900 hours on the meter.

By 2014-15 the pair of KSP 25’s had been in operation since early 90’s, and were now nearly 25 years old. The City of Stockton facility was now emerging from a turnaround and making critical investment upgrades. Stockton once again chose to invest in Schwing Bioset Piston Pumps and replace the aged pumps with brand new KSP 25’s in the dewatering building. The new pumps have the same durability to last another thirty years, and with upgraded safety and control features that offer easier remote operation and even longer wear part life.

The SBI field services team was also hired to remove the exiting units and re-install the new pumps. The pump system was replaced by SBI in full including; Hydraulic Power Packs, Twin Screw Feeders, Control Systems, and of course the Piston Pumps. The SBI crew was able to work seamlessly with Stockton personnel to not upset active onsite operations during installation. As such, the pumps were replaced in series to phase out the old system. A completely brand new turn-key cake pumping system will be turned over to the City of Stockton this year.          

To learn more about our piston pumps or this project specifically, contact a Schwing Bioset Regional Sales Manager, call 715.247.3433, email us, and/or visit our website here.


Tags: Piston Pumps, Wastewater Treatment, Municipal Pumps, Dewatered Sludge Cake