News from Schwing Bioset

Pima County, AZ, Tres Rios WRF Biosolids System Upgrades - Part Two: Live Bottom Cake Bins

 

Written by Josh DiValentino

 

Background: The district of Pima County, AZ, operates a total of eight wastewater treatment plants. The Tres Rios Water Reclamation Facility (WRF) is the centralized biosolids processing facility for all Pima County plants. Tres Rios WRF currently operates 24/7/365 at a 30 MGD capacity, with a projected flow of 50 MGD in 2030. The facility process is; BNR, Anaerobic Digestion, Dewatering, Pumping, Truck Loading, and Land Application of biosolids (cotton is common use). For nearly 20 years, Schwing Bioset, Inc. has provided solids handling solutions at Tres Rios with projects ranging from biosolids cake pumping and cake storage bins, to most recently, nutrient recovery and temporary Screw Press dewatering equipment.

 

Live Bottom Cake Storage: In 2012, the facility completed a Regional Optimization Master Plan expansion, which included upgrades to the centrifuge building and a new truck loading building. Prior to this expansion, dewatered cake was pumped (using the original Schwing Bioset Piston Pump) directly through a pipeline to the truck loading area. There was no intermediate storage capacity in the system on the dewatered cake side. Further, trucks could only be filled as fast as the cake pump could deliver cake, significantly reducing truck fill times.

 

Tres Rios Storage w-caption 2During the 2012 expansion, Schwing Bioset, Inc., supplied the new truck loading cake bins. Three (3) live bottom bins were provided, each with a capacity of 3,000 cubic feet of cake storage.

  • Bin Silo Sizing Details (each): Circular Design, 12’ diameter and 33’ tall storage area. Total height of 51’ including truck loading area.

Each bin utilizes a live bottom to deliver biosolids cake to the trucks below. The live bottoms are center discharging.

  • Bin Live Bottom Details (each): 18” diameter shafted, Twin Screws. Complete with 36” x 36” pneumatically actuated slide gates to control cake fill.

 

The top of the bins extend through the roof of the truck loading building. The bins provide storage capacity for dewatered cake and can fill trucks in less than 15 minutes when needed. The systems came complete with access ladders, safety railing, and ventilation connections for odor control. The bins have been in operation for nearly a decade, requiring only regular upkeep and maintenance to bearings and drive systems.

 

Click here to read more about our Products, then contact us to learn more about this project or find out how we can help your plant too.

 

Read Part One: Cake Pumping

Stay Tuned for More on Pima County Projects:

Part Three: Temporary Screw Press Dewatering

Part Four: NuReSys Struvite Management Project

 

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Tags: Biosolids, Wastewater Treatment, Water Reclamation Facility, Live Bottom Bins

The Maine Solution

 

When an upgrade to the biosolids dewatering component at the Westbrook/Gorham Regional WWTP was needed, a screw press has helped the facility dramatically reduce their sludge hauling/handling costs.

Written by Larry Trojak, Trojak Communications

Version also published in WaterWorld, June 2020

 

Schwing Bioset Dewatering Screw Press

 

When an upgrade to the biosolids dewatering component at the Westbrook/Gorham Regional WWTP was needed, plant personnel looked at several different available technologies. Handling secondary sludge alone is challenging, and after an extensive trial and evaluated bid process, they opted for a screw press from Schwing Bioset, Inc. Today, sludge leaving the plant is averaging just above 20 percent solids, and the Westbrook/Gorham Regional WWTP has dramatically reduced costs associated with hauling and landfilling their material. Are they pleased? To quote the locals: “Ayuh.”

 

Diversity in the District

The Portland, Me., Water District (PWD) manages its wastewater treatment through four facilities: East End, the largest plant in the state, which handles wastewater for the Portland metro and surrounding areas; Westbrook/Gorham Regional WWTP, which serves Westbrook, Gorham and a portion of Windham; Cape Elizabeth, which handles wastewater from 3,100 residents in the southern part of the town of Cape Elizabeth; and Peaks Island, which serves 600 island residents — a number that can swell to more than five times that in the summer tourist season. While the Westbrook/Gorham Regional facility is an extended aeration plant, each of the others utilizes a different technology for dealing with their biosolids, according to Steve Picard, the operations foreperson at the plant.

“Within the District, we are certainly varied in our approaches to wastewater treatment,” he said. “East End is a conventional aeration-type plant using clarifiers; Peaks Island is a sequencing batch reactor facility, and Cape Elizabeth is an oxidation ditch plant — they are all similar in many ways but different in others. The Westbrook/Gorham Regional plant was built in 1978. An upgrade to the plant’s aeration system is planned for later in 2020.”

Picard added that three-quarters of the existing plant will be upgraded — a move that will include the addition of new clarifiers mechanisms, a blower facility, and diffused air-type aeration equipment. To show how things have changed, the original plant’s price tag was $14 million; this modification alone is $10 million.

 

Planning Ahead

About two years prior to the plant upgrade, the Portland Water District saw the sludge disposal costs Westbrook was incurring and committed to improving the plant’s dewatering capability. Up until then, the facility, which is rated for 4.54 MGD but treats an average flow of about 3.2 MGD, took sludge from the bottom of the final clarifiers, pumped it to a gravity belt thickener where it was thickened to approximately 4 percent solids, and sent it to a 2.5 meter belt press.

“On a good day, that belt press would give us maybe 17–18 percent solids,” said Picard. “Unfortunately, because we deal strictly with an inflow of secondary sludge here at Westbrook, there weren’t many of those good days. To make matters worse, because we were sending that sludge to a trailer for transport to a landfill about three hours away, we were paying to haul a lot of water that didn’t need to be there. That had to change.”

For Schwing Bioset, finding out about the project was a classic case of being in the right place at the right time. For nearly 30 years, Westbrook has been using a Schwing Bioset KSP 10 piston pump to move sludge from the belt press out to the trailers — a distance of more than 70 feet. Word that they were actively seeking equipment to enhance their dewatering effort got the attention of a technician who happened to be on site.

“When I mentioned that we were about to go out to bid for dewatering equipment, the tech said that Schwing Bioset also made a screw press that could be a good fit,” said Picard. “He went back, told his people, and they were suddenly in the running for the bid along with several other manufacturers. Their timing couldn’t have been better.”

 

Natural Solution

After extensive testing of four manufacturers’ products and a competitive bid process, PWD selected an FSP 1003 screw press from Schwing Bioset.

“Because we already had the piston pump and power pack from Schwing Bioset, we thought that having a screw press from the same manufacturer — a company that we were already very satisfied with — could only work to our advantage,” said Picard. “However, they also outperformed the others we tested and were within our budget, so we felt confident that we’d made a good decision.”

Features that helped make the case for Westbrook included the unit’s low-speed operation — which enhances its lifespan — and automated control. Ease of regular maintenance was also key, including a split screen casing to simplify access for any maintenance activities such as replacing the sealing lip and eventually the screens. Both items can be replaced without having to remove the screw.

“In addition, because the entire operation is now enclosed, all the odor associated with dewatering is contained,” said Picard. “And finally, we liked the fact that the Bioset press could be cleaned while in use, so the dewatering operation would not be impacted by it. All these played a role in our decision.”

 

Getting the Numbers Up

Once the new press was in place (the installation was completed by the same contractor that handled their belt press 28 years ago), Picard and his team were initially stymied trying to find the polymer that would give them the numbers they were anticipating. Using the same product they ran with the belt press resulted in no change: solids in the 17 percent range.

“We suspected that was because, unlike the screw press, the belt press had little to no agitation to it and it held the floc together easily,” he said. “However, by the time we tested our fourth polymer, we started getting solids numbers up in the 19–20 percent range. Connecting the screw press to the polymer injection system we had used with the belt press — then adding two more injection points — got us a bit closer.”

In addition to polymer optimization, there was a period of learning how the new system could be successfully operated at the plant. Doing minor adjustments to the injection system prior to running the screw press for several days without making any changes allowed workers at the plant to verify what worked and what didn’t.

“We were closely tracking our polymer feed rate and the cake coming out of the system and, when we started to break 20 percent solids, knew we were on to something,” Picard said. “We learned that, where the polymer is injected into the system is hugely important. Here, in an area one level down from the press, the polymer goes into a check valve which gives it a good primary mix with the sludge, then comes up and into a huge reaction tank equipped with a variable speed mixer. Using that configuration, the difference was impressive: the 2.5–3 percent feed rate at which we used to feed the belt press didn’t even tax the screw press. Instead, we found out the screw press runs great at 4–4.5 percent, which was a nice plus for us.”

 

Biosolids  Westbrook Wastewater Treatment Plant

 

The Better Choice

With their tweaks in place, Picard and his team at Westbrook saw a continued uptick to the point where they’ve averaged just over 20 percent solids out of the screw press for just over a year now and have seen that number climb as high as 22.5 percent or 24 percent on some days. That has resulted in a net savings — even with added polymer costs factored in — of about $40,000 annually. To the uninitiated, an increase in solids of up to 5.5 percent might not seem substantial. However, that number still represents a 25 percent increase in performance.

And, said Picard, context is key.

“The difference between the two processes is particularly significant when you remember that we are dealing with a straight secondary sludge which is very hard to dewater,” he said. “Even Schwing Bioset rated the screw press at only 19–20 percent under these conditions.

 

Anticipating Change

Today, Westbrook is producing about 30 tons of a better dewatered product every day they dewater during their five-day-a-week operation. By reducing the amount of water in each load, the three-hour trip to the landfill for disposal is far more cost-effective.

“Disposal for us is a costly operation and the Schwing Bioset press has helped significantly knock down those costs,” said Picard. “In addition, there was a good deal of belt spraying, wash water, etc., associated with the previous process, resulting in a constant mist in the air. The place was continually wet where today, things are clean and dry.

He adds that, throughout this conversion process, PWD leadership was outstanding in working with them — giving them support and encouragement all along the way.

“On that note, when we did the screw press install, we kept the belt press here for a year as a backup in case the Bioset didn’t work,” said Picard. “Eventually that belt press was sold for scrap — I guess that says it all.” 

 

Click here to read more about our Products, then contact us to learn more about this project or find out how we can help your plant too.

 

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Tags: Biosolids, Screw Press, Dewatering, Wastewater Treatment Plant

Pima County, AZ, Tres Rios WRF Biosolids System Upgrades - Part One: Cake Pumping

 

Written by Josh DiValentino

 

Tres Rios Storage w-caption 2Background: The district of Pima County, AZ, operates a total of eight wastewater treatment plants. The Tres Rios Water Reclamation Facility (WRF) is the centralized biosolids processing facility for all Pima County plants. Tres Rios WRF currently operates 24/7/365 at a 30 MGD capacity, with a projected flow of 50 MGD in 2030. The facility process is; BNR, Anaerobic Digestion, Dewatering, Pumping, Truck Loading, and Land Application of biosolids (cotton is common use). For nearly 20 years, Schwing Bioset, Inc. has provided solids handling solutions at Tres Rios with projects ranging from biosolids cake pumping and cake storage bins, to most recently, nutrient recovery and temporary Screw Press dewatering equipment.

 

Cake Pumping:  Since the early 2000’s to 2012, the Tres Rios WRF had used a piston pump for biosolids cake conveyance to truck loading. In 2012, the facility completed a Regional Optimization Master Plan expansion, which included an upgrade to the centrifuge building and loading building. The upgrade design replaced the existing piston pump with progressive cavity pumps dedicated to each of the three new centrifuges.

After 6 years of struggling with excessive downtime associated with the progressive cavity pumps, the 10+ year-old piston pump was pulled from storage, sent to Schwing Bioset, Inc. to be rebuilt and reconfigured to fit the existing building, and installed to replace one of the progressive cavity pumps.

Since its reinstallation, the plant has used the piston pump as its primary pump, reducing the downtime and maintenance costs associated with the progressive cavity pumps. The facility no longer needs to de-rate the centrifuges and has been able to dewater the biosolids to a higher percent solids content when using the piston pump, significantly reducing hauling costs. The subsequent uptime and increase in dry cake solids production justified the capital cost of buying an additional Piston Pump, as the payback was determined to be 2 years. One progressive cavity pump will remain in service as an emergency backup for pumping thickened sludge, which is usually thickened from 6% to 8% solids.

The second new Piston Pump will come online in 2020. The Schwing Bioset, Inc. Engineering Team also worked with the district to perform a complete pipeline analysis of the existing cake pipeline. This identified the pipeline upgrades required to re-certify the pipeline for higher pumping pressures, resulting from higher cake solids and higher flow via the Piston Pumps to Truck Loading. This pump technology conversion clearly illustrates that while the initial capital expense of a piston pump is higher than a progressive cavity pump, the long-term expenses over the operating life of the equipment, when factoring in hauling expenses, maintenance costs, and operational downtime, heavily favor piston pump technology.

 

Schwing Bioset Piston Pump

 

For more information on this project, read the paper below or contact us.  

 

Additional Info: Biosolids Cake Pumping Life Cycle Analysis - A True Operators Story

Stay Tuned for More on Pima County Projects:

Part Two: Live Bottom Bins

Part Three: Temporary Screw Press Dewatering

Part Four: NuReSys Struvite Management Project

 

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Tags: Piston Pumps, Biosolids, Biosolids Piston Pump, Water Reclamation Facility

Screw Press Proves Efficient in Dewatering MBR Sludge

 

Written by Tom Welch

Version also Published in TPO Magazine, August 2019

 

The Decatur, AR, WWTP had existing dewatering technology that proved to be undersized and inefficient. With the additional demands of a new plant upgrade, Operations staff were struggling to meet current dewatering requirements.

The Design Build team and Owner selected an FSP 802 screw press from Schwing Bioset to replace the existing equipment. The new equipment was installed in the same building with primarily service connection modifications. The screw press started operating in November of 2018.

The improvements in the dewatering operations are remarkable, as it is saving Decatur operational expenses in every category. Dry solids content of the dewatered biosolids have improved from an average of 13% to 17%, resulting in less cake to haul. Solids capture rate has improved from less than 80% to 95%, resulting in a lower return load to the plant. Polymer usage is now at 18 pounds active per dry ton, which is well below the consumption rate of the previous technology reducing polymer expenditures.

In addition to these performance improvements, the dewatering capacity has more than doubled. Where it used to take at least two days to load a 25-ton trailer, the plant can now fill a trailer in 6.5 hours, reducing operator efforts in turn. 

With the widest range of machine sizes for several applications, and mobile pilot units available for testing your materials, Schwing Bioset is your comprehensive solutions provider for dewatering.

Click here to learn more about our products or contact our regional manager closest to you.

 

Decatur Dewatering Screw Press

 

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Tags: Biosolids, Screw Press, Dewatering, Membrane Bioreactor

Screw Presses Help Plant Reduce Maintenance Costs

 

Written by Chuck Wanstrom

Version also Published in TPO Magazine, August 2018

 

The city of Bradenton, Florida, operates a wastewater treatment plant that processes roughly 8 million gallon per day. The plant had historically aerobically digested their biosolids and dewatered them to 15% dry solids content using two, 2.0-meter belt filter presses. Due to the age of the belt filter presses, the maintenance expenditures were continually increasing and were creating a burden not only with expenses, but also with personnel time to keep the equipment functioning.

Bradenton began a search to identify new dewatering techniques that could replace the aging belt filter presses.  Several pilot studies were completed, and Schwing Bioset was invited to run our screw press pilot. The pilot proved successful with results of up to 21% dry solids. The Schwing Bioset screw presses were also able to fit within the confines of the available space on the second floor of the existing dewatering building. 

The Schwing Bioset equipment was chosen as the best value and was procured under a sole source contract. The two new FSP902 screw presses were designed into the existing dewatering building and were commissioned early in 2018. The dewatered biosolids exceed the old belt presses cake performance and reduces the city’s hauling and disposal costs while at the same time reducing the amount of wash water required and significantly reducing the maintenance load to city staff. 

Learn more about our screw presses or contact our regional manager closest to you.

 

Bradenton Screw Presses

 

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Tags: Biosolids, Wastewater Treatment, Screw Press, Dewatering, screw presses

Sugar Creek WWTP Screw Press Records Impressive Data

 

Written by Tom Welch, November 2018

The Sugar Creek WWTP, owned by the Sangamon County Water Reclamation District located in Springfield, IL, has two Schwing Bioset model FSP 1102 screw presses and our Class B alkaline stabilization process. The screw presses dewater the plant’s aerobically treated biosolids and the downstream equipment produces the alkaline stabilized Class B biosolids. These biosolids are then windrowed in the District’s storage shed and eventually land applied for beneficial use. Data recorded from a recent site visit on a single screw press in operation was impressive and can be seen below.

Incoming Flow: 280 gpm
Incoming % DS: 1.5%
Throughput: 2,100 lbsdry/hr
Polymer Dose: 12 lbs/ton
Output % DS: 22%
Capture: >95%

 

Check out the included photos and operational videos, which show an overview of the installation and the equipment in action. 

Contact your Schwing Bioset Regional Sales Manager to learn more about how our biosolids management systems may be able to improve your current processes.

 

  IMG_0453_small  IMG_0452_small

 

 

 

 

 

 

 

 IMG_0461_small  IMG_0459_small  

 

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Tags: Alkaline Stabilization, Biosolids, Screw Press, Dewatering

Dewatering with a Screw Press at Bradenton WWTP

 

Written by Chuck Wanstrom, May 2018

The city of Bradenton, Florida, operates a wastewater treatment plant that processes roughly eight million gallons per day. The plant had historically aerobically digested their biosolids and dewatered them to 15% dry solids content using two, 2.0-meter belt filter presses. Due to the age of the belt filter presses, the maintenance expenditures were continually increasing and creating a burden not only in expenses, but also on personnel time to keep the equipment functioning.

Bradenton began a search to identify new dewatering techniques that could replace the aging belt filter presses. Several pilot studies were completed and Schwing Bioset was invited to run their screw press pilot. The pilot proved successful with results of up to 21% dry solids. The Schwing Bioset screw presses were also able to fit within the confines of the available space on the second floor of the existing dewatering building. 

The Schwing Bioset equipment was chosen as the best value and was procured under a sole source contract. The two new FSP902 screw presses were designed into the existing dewatering building and were commissioned early in 2018. The dewatered biosolids exceed the old belt presses cake performance and reduces the city’s hauling and disposal costs while at the same time reducing the amount of wash water required and significantly reducing the maintenance load to city staff. 

To learn more about this project or our screw presses, contact a regional manager or email us.

 

1  DSCN8025

 

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Tags: Biosolids, Screw Press, Dewatering, Wastewater Treatment Plant

Metro WWTP Upgrades Piston Pump Sludge Flow Measurement System

 

Written by Chuck Wanstrom, March 2018

 

The Metro WWTP, operated by the Metropolitan Council of Environmental Services (MCES), located in St. Paul, MN, has an average daily flow of 215 million gallons per day (MGD) of incoming flow. Prior to 2004 the plant had been utilizing multi-hearth incinerators to burn their biosolids. A new incineration facility utilizing fluid bed technology was commissioned in 2004 and included a dewatered biosolids storage and feed system supplied by Schwing Bioset, Inc (SBI).

The feed system included four sliding frame silos providing intermediate storage of dewatered cake to provide a buffer in centrifuge and incinerator operations. Each of the four sliding frame silos were equipped with two KSP 45V(HD)L piston pumps to transport the dewatered cake to the incinerators. Each piston pump is equipped with a dual discharge to split the biosolids flow to multiple incinerator injection points, as well as a Sludge Flow Measuring System (SFMS) to measure within 5% the amount of biosolids being pumped into the incinerator. The SFMS is a critical piece of the operation as this is required to satisfy US EPA reporting requirements. This proven equipment configuration and flow measuring system has been utilized at numerous other facilities across North America for over 20 years.

Schwing Bioset has recently developed an improvement in its SFMS to reduce the possible sources of error that can be introduced with variations in pumping speed during operation. This next generation of SFMS results in an even more accurate means of recording and reporting biosolids flow and is further evidence of Schwing Bioset’s commitment to developing and improving its technology to better serve its family of customers. After nearly 15 years of reliable service, the Metro plant, and its continuing commitment to excellence, is currently in the process of performing upgrades throughout its Solids Management Building and is converting its piston pumps to this next generation of flow measurement. Schwing Bioset looks forward to many more years of supporting MCES and to the continued success of this impressive facility.

If you are currently using an SBI pump equipped with our SFMS and would like more information on upgrading your equipment to the latest generation of flow measurement, please contact us at (715) 247-3433 or schwingbioset.com/contact-us.

 

WWTP Schwing Bioset Piston Pump

 

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Tags: Piston Pumps, Biosolids, Wastewater Treatment Plant

Push Floor Bin and Biosolids Pumps Help Plant Stabilize Operations

 

Written by Chuck Wanstrom

The City of High Point, NC, was previously pumping biosolids to an incinerator using hydraulically actuated piston pumps supplied by another manufacturer. These pumps were aging and the city couldn’t reliably obtain spare parts to support their operation. Additionally, the wastewater treatment plant occasionally struggled with operations as it didn’t have any buffering capacity for the dewatered biosolids ahead of the piston pumps. In an effort to solve the support issues with the existing equipment and stabilize operations, the city solicited bids from consulting engineering firms to update and improve their process.

The selected engineer began surveying biosolids handling systems available in the market and with input from their Client, settled on a push floor storage bin and piston pump arrangement as offered by Schwing Bioset. With over 30-years of experience in biosolids storage and conveyance, and numerous successful installations to its credit, Schwing Bioset was the logical choice to provide the design and equipment for this retrofit application.

A new push floor bunker with 60 yards of storage capacity was supplied to handle the centrifuge dewatered biosolids. Directly coupled to the bottom of the new push floor bunker are two Schwing Bioset model SD 350 screw feeders and KSP 17 piston pumps. The piston pumps have a dual-discharges that allows the biosolids flow to be split and fed into the incinerator at a total of four injection points for more efficient incinerator operations as well. If the incinerator goes down, biosolids can also discharge to a new truck loading facility.

To learn more about our pumps and push floor bins, visit our Products page, Contact Us, visit our Website, or find us on social media.

 

High Point Piston Pumps  High Point Truck Loading

 

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Tags: Piston Pumps, Biosolids, Wastewater Treatment, hydraulic push floor bin

Southerly Sets The Standard with Sludge Disposal Efforts

 

Schwing Bioset Application Report 14, Columbus, Ohio

Written by Larry Trojak, Trojak Communications

Version also published in WE&T Magazine (click to view)

 

Pumps and sliding frames allow options for effective disposal of cake from Columbus, Ohio, operation.

Wastewater treatment plants can distinguish themselves in any number of ways: by the volumes they can handle, by the number of industry awards they have earned, by the manner in which they handle an interruption in “business-as-usual”, and so on. They can also do so by demonstrating a creative, effective and successful effort to use or dispose of the biosolids they generate. Given those criteria alone, the Southerly Wastewater Treatment Plant could likely be seen as one of the premier WWTPs in operation today. Just coming off a five-year, $350 million expansion which nearly tripled its peak capacity from 114 mgd to about 330 mgd (built-in contingencies for further expansion can take the plant as high as 550 mgd), the plant services the majority of the greater Columbus area. State-of-the-art in every regard, Southerly is poised to build upon an already impressive reputation that has won them numerous National Association of Clean Water Agencies (NACWA) awards for plant and employee performance.

Columbus_Southerly_1.jpg

But it is also its innovative sludge disposal program that separates Southerly from super-plant wannabes. Using a quartet of heavy-duty pumps and a number of sliding frame components (all from Schwing Bioset, Inc. [SBI] Somerset, WI) cake can either be routed directly for incineration or sent to a pair of storage silos. Once in the silos, the material is readily available for truck-loading and transport, either to an already-successful composting operation run by the department or directly to the landfill.  Options, it seems, are the hallmark of this successful operation. 

Change They Can Use

Built in 1967, the Southerly WWTP is one of two plants serving the Columbus metropolitan area (the other being the nearby Jackson Pike WWTP). The current plant expansion which so dramatically increased overall capacity, also increased volumes in the solids handling area. New centrifuges, installed a number of years in advance of that expansion, handle that increase nicely, 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,” he says. 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 20-25%, a nice improvement over the 17-21% solids content with the older system.”

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

Columbus_Southerly_3.jpg

The Route To Disposal

Getting cake to the point where disposal options are available is a function of Southerly’s pumps and silos. As material exits the centrifuges, it is routed to any of four Schwing KSP 45V(HD)L-SFMS pumps which direct it to the appropriate area. Where that is, varies greatly according to need.

“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,” says Carmon “Skip” Allen, Solids Supervisor 2. “Obviously that can vary from day to day. The balance of the material—we can do anywhere from 5.5 tons up to 9 tons an hour—is then sent for incineration. But we know at all times what is going to the silos for storage and what’s getting burned.”

The sludge pumps at Southerly are designed to generate a force sufficient to move cake the long distances needed for either incineration or storage. He says it is easily 300 feet to the multi-hearth incinerators (which have operating temps of 1400°F), and about 400 feet to the storage silos. Equipped with Schwing Bioset’s Sludge Flow Measuring System, the pumps are able to measure to within +/-5% the amount of sludge that is pumped to the incinerator. This simplifies their USEPA reporting requirements for their incinerator operations.

“Material headed to the silos, however, has an additional challenge to overcome,” says Allen. “Once there, the cake has to go straight up another 100 feet 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 1,100 psi for each pump, those extended distances at Southerly prompted Schwing Bioset to make accommodations to help move the sludge along. To do so, they added a “slip ring,” or pipeline lubrication system. Schwing Bioset’s unique design includes a 360 degree annular groove that evenly injects a thin film of water around the entire annulus of the pipe that separates viscous and sticky materials from the inner wall of the pipeline. The end result is a reduction in friction loss in the pipeline, and lower—in some cases better than 50% less—pipeline operating pressures.

Additional benefits include a savings in energy by reducing the demand on each pump and hydraulic unit, and, because of the reduction in pipeline friction, an increase in wear part life. While other systems try to address the friction issue through the use of as many as four drilled ports which inject more fluid, this offsets a percentage of the gains made by the centrifuges. Still other designs mix polymer with the water to help reduce pressure which, while effective, adds both up-front and perpetual costs to the operation.

Tom Thomas, Maintenance Supervisor 2 at Southerly, says the reduction in friction has also shown benefits in wear part life for the pumps—a fact that is borne out in similar results at Jackson Pike. “We run these pumps round the clock and, even with that 24/7 operation, parts such as the pumping rams, poppet valve discs and seats are getting six months of wear. That’s about 4,000 hours of wear part life, which is outstanding given what they’re being asked to pump.”

Silo Efficiency

As mentioned, the SBI sliding frame silos offer a storage option for cake headed either to the landfill for disposal or to the compost site. Prior to their installation, Southerly relied upon a smaller holding vessel known as “the pit,” a belt-fed, hopper-equipped component that used a series of screws to feed a truck sitting under the discharge chute. City officials say the new silos are larger (providing about 75% more capacity) as well as far more efficient, thereby reducing truck loading times from 45 minutes with “the pit,” down to only five minutes. This was an important criterion when selecting equipment.

Because the City pays a contractor to haul the biosolids, reducing loading times lowers overall hauling costs—the trucks now spend more time hauling and less time waiting to be loaded. The net result is more trucks loaded per day (and a lower cost to do so.) In addition, because of that added storage capability, the composting operation now has the option of drawing material solely from Jackson Pike, if necessary. "Anytime you can reuse something rather than just burying it or burning it, you are making a positive impact," says Assistant Plant Manager Jeff Hall.

“Today, we are reusing about one-third of the solids we handle through the composting operation,” says Hall. “That’s obviously good from an economic standpoint, since we are generating revenue from a product that was once simply discarded. However, it is also a plus from an environmental perspective."

The concept of the sliding frame silo is simple, yet very effective. Hydraulic cylinders move an elliptical frame across the silo floor. The frame’s action not only breaks any bridging that can occur over the extraction screw, it also pushes and pulls material towards the silo extraction screws for discharge into trucks.

Allen says the sliding frame silos were a nice addition to the operation. “Each silo holds better than 1,500 tons 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. It’s really all about flexibility and these silos afford us that.”

Due to the sheer size of the silos, they are each equipped with three extraction screw conveyors at the bottom which allows the trailers to be evenly loaded without having to be jockeyed back and forth.

The silos also include an odor and splash control shroud that pulls fumes directly off the trailer, thereby minimizing the need for odor control in the truck loading building. In addition, it helps reduce the chance of material splatter during load-out, and confines any such instances to the area immediately adjacent to the trailer, which makes periodic cleanup of the area much easier.

Allen adds that they also use SBI sliding frames on hoppers in advance of the pumps which feed the incinerator. Doing so provides a wide spot in the process line enabling them to maintain steady incinerator operations for several hours in the event of any upset condition with the centrifuges.

Sibling Growth

Southerly WWTP’s growth is being mirrored in the expansion of its sister plant, Jackson Pike WWTP, located a mere seven miles from Southerly’s facility. That plant also installed SBI equipment for similar end uses, but because its capacities are less, scaled down the size of that equipment. So today, Jackson Pike uses a quartet of KSP 25 V(HD)L pumps, rather than the 45s in use at Southerly and powers them with a 100hp power pack compared to its 150hp counterpart. The silos, though smaller in height, are of the same design and offer the same performance benefits as Southerly’s. Once the expansion at Jackson Pike is complete, the two plants will effectively meet all of Columbus’s wastewater treatment needs for decades to come. For Skip Allen, seeing construction at Southerly come to an end after nearly six years is a welcome relief.

“We are all really happy about the changes that have taken place here; there’s no doubt about that. But it feels like we will now finally be able to get back into the treatment plant business. With construction done, we have a big headache behind us, we have a great operation in place, and we’re doing good things for the residents of Columbus. That’s not a bad place to be.”

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To download the entire #14 application report for Columbus, Ohio, click here.

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

 

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Tags: Biosolids, Wastewater Treatment, Municipal Pumps, Sliding Frame Silos, Truck Loading