News from Schwing Bioset

New Piston Pumps Help Stabilize Metro Sewerage District Incinerator Operations

 

Written by Tom Welch

Version also published in TPO Magazine, March 2021

 

Piston pumps are used to feed dewatered cake solids to the incinerators at the Metropolitan Sewerage District of Buncombe County, North Carolina, located in Asheville, NC. The original pumps were supplied in 1993 and were sequentially replaced in 2005 and 2007. Due to the growth experienced in the area over nearly 30 years and the continued projected population increase, the pump capacity had to be nearly doubled in the most recent expansion. 

With nearly three decades of exemplary performance for the MSD, Schwing Bioset was again selected to provide the cake pumping equipment package and has recently supplied new KSP 17 piston pumps to feed the dewatered cake solids to the incinerators. The package has performed well for the wastewater plant.

The package included upsized feed hoppers with a delivery piping and actuated ball valve system that can feed either the incinerator or be bypassed to truck loading. To reduce pressure in the pipeline, Schwing Bioset’s proprietary pipeline lubrication design was incorporated to reduce line pressure, extend wear part lives, and minimize the power draw of the hydraulic power pack.

The original pumps had a single discharge line feeding the incinerators. The new pumps were delivered with a unique dual discharge system that splits the flow leaving the pump and enables the incinerator to be fed from multiple locations to stabilize incinerator operations. To accommodate EPA regulations, Schwing Bioset also provided its patented Sludge Flow Measuring System that measures pump output to within +/- 5% of the feed going to the incinerator.

 

Schwing Bioset Piston Pump   Schwing Bioset Power Pack

 

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: Piston Pumps, 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

Myra Falls Mine Opening Again with Updated Paste Pumps

 

Written by John Brown, April 2018

The Myra Falls mine, owned by Nyrstar, is located in a provincial park in central Vancouver Island (British Columbia) and is linked only by a 90 km asphalt road to the port of Campbell River. In 2002, Myra Falls constructed a paste plant to manage their tailings that included two KSP-110V(HD)L pumps with a maximum capacity of 82 m3/hr at 8.62 MPa. Each pump was equipped with hydraulic units that had a capacity of 600 HP.

For years the KSP 110’s had been pumping paste-tailings material nearly 2 miles to either a surface tailings pond or back underground to the stopes through an eight-inch pipe without any problems. Myra Falls relied on Schwing Bioset for over seven years of operation and service of the pump systems.  Economic conditions then led to the suspension of mining operations which are now scheduled to resume in 2018.

To keep the operation running as smoothly as before, an engineering analysis was performed on the existing facilities to evaluate the equipment and processes in place.  As part of this analysis, Nyrstar decided to increase the capacity of their operation by replacing the KSP 110 pumps with new KSP 140’s that provide nearly 30% more capacity and to recondition the existing power units.  The two power packs for the KSP 110’s were sent back to the Schwing Bioset factory and these 15 year old power units will be updated with the newest hydraulic designs and componentry.

The new KSP 140’s will also be using Schwing Bioset’s proprietary Ideal Control Circuit (ICC), which reduces paste flow velocity changes at the end of each pumping stroke to mitigate the pressure surges that can be seen in paste pipelines. This internal dampening system is achieved with simple position sensors and programming and avoids the complexities of other dampening systems available on the market.

The project is expected to be completed in July of 2018. For more info on our Mining Pumps, contact John Brown or visit http://www.schwingbioset.com/mining-pumps.

 

Schwing Bioset Piston Pump for Myra Falls Mine

(Photo shows one of the Myra Falls pumps in the Schwing Bioset facility being prepped to ship to the job site).

 

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Tags: Piston Pumps, Mining Pumps, Paste Pumps

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

Schwing Bioset is Exhibiting at WEFTEC 2017

 

Schwing Bioset, Inc. (SBI) is looking forward to exhibiting at the 2017 WEFTEC Event in Chicago on October 2-4. 

Please be sure to stop by our booth (#2007) while you're on the exhibit floor. We will be displaying a dewatering screw press, as well as two new pieces of equipment.

Our new Membrane Bioreactor (MBR) filtration systems for water and wastewater utilize hollow fiber membranes. The unique end-free cartridge design provides an economical alternative to traditional longer fibers.

We are also debuting our new SBI Solutions system. This pre-packaged system is configurable to produce either Class A or B Biosolids in a convenient, pre-engineered skid mounted unit. The system is a compact, modular unit including a piston pump combined with the Bioset process, and optional screw press dewatering capabilities for an all-in-one package.    

MBR.png  SBI Solutions.png

 

 

 

 

 

 

 

The SBI team members attending the show include Executives, Regional Sales Managers, Aftermarket Support personnel, and more. If you'd like to meet with one of our team members, please email us and we'll put you in touch with the appropriate person.

Read about our Nutrient Removal and Struvite Harvesting, Dewatering Equipment, Piston Pumps, Bioset Process and Class A Biosolids, our new products, and other products hereand then stop by booth 2007 to learn more!

Visit the conference website to view the event details and exhibition map: http://www.weftec.org. Here is the Schwing Bioset listing for the show.

We hope to see you at WEFTEC 2017!


For more than 30 years, Schwing Bioset, Inc. has been helping wastewater treatment plants, mines, and industrial users by engineering solids handling solutions. Schwing Bioset’s custom-engineered solutions can be found in over a thousand facilities across North America and around the world.

Our products include, among others, sludge, industrial, and tunnel piston pumps, screw presses, nutrient removal and management, membrane bioreactors, sliding frame and push floor silos, fluid bed drying products, Bioset process for Class A Biosolids, container wagons, and screw conveyors. We also offer on-site demos, spare parts and equipment maintenance services, and training. 

 

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Tags: Bioset Process, Piston Pumps, Events, WEFTEC, Screw Press, Membrane Bioreactor

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

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

City of Orlando WWTP Utilizes Schwing Bioset Piston Pumps in Class AA Process

 

City of Orlando, FL, Conserv II WWTP Utilizes Schwing Bioset KSP 25 Piston Pumps in Class AA Biosolids Process

Written by Tom Welch, December 14, 2016

The City of Orlando, FL, Conserv II WWTP became aware of the Schwing Bioset process and immediately saw the potential it had to meet all of their requirements for both short and long-term implementation.  In addition, Schwing Bioset could offer conversion of the stabilized Biosolids to a licensed commercial fertilizer product.  The City staff visited current Bioset operations in Florida and were impressed with what they saw and with the simplicity of the process.  The City conducted an in-house feasibility study that considered Bioset and other technologies and concluded that Bioset was the preferred treatment process.

The current dewatering facility has four belt filter presses that discharge onto two belt conveyors that converge onto one common belt conveyor that takes the dewatered Biosolids to truck loading.  The decision was made to move away from the common belt conveyor to make the process more robust.  A KSP 25 piston pump was added at the end of each belt conveyor.  The two pumps are utilized to transfer the dewatered cake to the Bioset (Class A alkaline process).  The Bioset process also utilizes a third KSP 25 pump as the heart and soul of the system to blend the chemicals needed for the Class A process and pumps the end product into a plug flow reactor and ultimately out to two truck loading areas.  These pumps are programmed to work together to make sure that a consistent flow of Biosolids can be treated to Class A status through the reactor.

To learn more about our pumps and Bioset process, or this project specifically, contact this blog’s author, Tom Welch, and/or visit our Products page. For other inquiries, call 715.247.3433, visit our website, or find us on social media.

Schwing Bioset Piston Pump

 

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Tags: Bioset Process, Piston Pumps, Class 'AA' Biosolids, Wastewater Treatment

Solving Several Challenges with One Schwing Bioset Solution

 

Written by Miguel Jahncke, March 10, 2016

In late 2012, Volcan Compania Minera S.A.A.’s Victoria mineral processing plant, located in the Yauli district, department of Junin in Peru, was facing a number of challenges including the approval of their Environmental Impact Statement for the capacity expansion from 2,400 to 4,000 tpd of ore.

The project also required the expansion of the Rumichaca Tailings site to accommodate the increased production levels. Pumping thickened tailings, rather than conventional tailings, was determined to be the best long-term and financial solution to handle the mining rejects. The project continued to evolve in that direction. 

In mid-2014, when the final solution for the thickened tailings transport was being evaluated, it was determined that the solution offered by Schwing Bioset, its model KSP440 piston pump, was ideal for the project for the following reasons:

  • The KSP 440 unit is capable of the required maximum flow of 185 m3/hr as well as reduced flow of 92 m3/hr when at low plant production rates, which is expected at certain times by idling a module within the pump.
  • Half of the pump can be idled while half continues to operate allowing for preventive maintenance to be performed while operations continue at a slower pace or to accommodate unscheduled downtime.
  • Elimination of additional and costly stand-by equipment, with the modular pump arrangement.
  • Drastic reduction of water hammer in the discharge line without the use of Pulsation Dampeners through PLC synchronization that monitors and adjusts the timing of the pumping strokes.
  • Electric motor and hydraulic redundancy in the power pack allowing partial capacity in the event of unscheduled maintenance.

To learn more about this project specifically or our mining pumps, please contact us, call 715.247.3433, and/or visit our website here: SBI Mining Pumps.

 

Rumichaca_mining pumps.jpg 

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Tags: Piston Pumps, Mining, Mining Pumps, Mining Paste

How Transitioning to Class A Biosolids Saves Money

 

Published in TPO Magazine, February 2016. Written by Larry Trojak.

 

A southwest Florida treatment plant turns to lime stabilization to create Class A biosolids for land application and cuts handling costs significantly.

Cost-effective handling of biosolids is essential to clean-water plants’ economic and environmental performance.

The Immokalee Water and Sewer District in Florida faced a biosolids challenge in 2006. The district had been using drying beds to create Class B biosolids and spending about $500,000 a year to dewater and haul excess material from that process to a landfill.

Facing a change in regulations on land application of Class B material, and wanting to reach the biosolids’ full economic potential, the district looked at alternatives. The ultimate solution was a facility redesign centered on using the Bioset process (Schwing Bioset) to create Class A biosolids. As a result, the district has reduced handling costs by more than two-thirds and produces a Class A product for beneficial use.

Anticipating change

Located about 30 miles southeast of Fort Myers, the heavily agricultural Immokalee district is home to about 24,000 residents. Its wastewater treatment plant was expanded in 2013 from 2.5 mgd to 4.0 mgd design capacity. Until fairly recently, it generated 23,500 gallons of Class B biosolids per day at 1 to 1.5 percent solids.

Gary Ferrante, P.E., an engineer with the Greeley and Hansen engineering firm, says a number of factors in 2006 led the district to review its biosolids operation. “Immokalee’s plant was originally designed with a half-dozen drying beds in which a Class B biosolids was created and used on permitted area farms,” he says.

“While that was effective, the facility is next to a school, which repeatedly complained about students’ health risks and odor. The district later learned that the U.S. Department of Agriculture and the Florida Department of Environmental Protection were considering changes to biosolids land application regulations (passed in 2010 as Florida Biosolids Regulation Chapter 62-640 F.A.C.). All that prompted the district to hire a consultant to look at alternatives.”

Lots of options

Based on recommendations from the consultant’s report, in 2007 the district contracted with Synagro Technologies to dewater the Class B biosolids and haul it to a landfill more than 100 miles away. In time, rising prices and an increase in biosolids volume raised annual costs from $309,000 to more than $470,000, providing incentive for the district to pursue other options.

“Working with the district, we put together a couple of proposals and a couple of scenarios within each proposal,” says Ferrante. “The first one covered the design/build/finance of a biosolids facility at the existing location. Options under this plan included handling material from Immokalee only, as well as accepting material from Collier County and making Immokalee a regional processing facility. The second proposal had an outside entity leasing land from the district and constructing a Class A regional processing facility on it.”

An option under that proposal included a continuation of the contract dewatering program while the regional facility was taking shape. In the end, the district chose to establish a turnkey processing facility for its own biosolids sludge only and selected the Bioset process to deliver Class A material.

Schwing Bioset - Bioset Process  Schwing Bioset - Bioset Process

Class A operation

At the new facility, material exits the primary treatment facility’s sludge holding tanks at 1.5 percent solids and is fed directly to a high-performance screw press, selected for a number of reasons, including its relatively compact design.

“Because of the limited availability of usable land, a small footprint for the entire biosolids system was a major consideration, and the Bioset screw press fit in nicely,” Ferrante says. “We’ve found it to be an outstanding dewatering tool, yet extremely efficient in power usage.

“The belt press we looked at would have taken the material from 1.5 or 2 percent solids up to 8 to 10 percent. A centrifuge might get that up to 20 percent, but the electricity costs would be much higher. The screw press takes the material up to 16 percent solids. It uses twin augers and a changing pitch on the screws to advance the material and remove the water. Because it takes far less energy to turn those two screws than to power a centrifuge, the savings in power consumption can be significant.”

Another feature is that district personnel can wash the screw press down while it remains operational, says Michael Castilla, service technician 1: “The Bioset screw press has an automated self-cleaning function which in itself is nice. However, when we have a situation that calls for additional cleaning, we can simply push a button and a cleaning cycle will start. That’s a bonus. To shut a press down for maintenance or repair could cost us a half-day’s performance.”

Positive reaction

After dewatering, untreated biosolids are taken via screw conveyor to a twin-screw mixer in which quicklime and sulfamic acid are added. The mixing resolves issues such as unreacted lime in the final product and yields a highly homogeneous material. From the mixer, a Schwing Bioset KSP-10HKR pump feeds material into a 56 1/2-cubic-foot reactor in which heat from the acid and quicklime reaction raises the pH, stabilizing the mixture and creating a product that meets both Florida Chapter 503.33 and U.S. EPA Class A requirements.

“Retention time in the reactor is about 30 to 45 minutes at temperatures in the range of 122 degrees Fahrenheit,” says Ferrante. “The plant wastes sludge for 16 hours a day, consistently generating about­­­­­ 11 dry tons of the Class A material weekly and doing so at a markedly lower cost than for outright hauling and landfilling.”
Castilla adds that the system’s ease of operation was also key to getting up to speed quickly.

“It is very intuitive and simple to operate,” he says. “However, Schwing Bioset still went to great lengths to ensure that people involved in day-to-day operation are comfortable with it, have a handle on the maintenance routines, and so on. Ian Keyes from their Wisconsin office spent time here mentoring me to such a degree that there’s very little about the system I don’t understand.”

The Class A material exits the system, is loaded onto a manure spreader and taken to an area field where it is applied in place of fertilizer. Eliminating those fertilizer costs alone has saved about $50,000 per year.

In addition to lower costs, the district benefits from a much cleaner, less maintenance-intensive, more environmentally friendly operation. Dust from the lime-based process is controlled using hard-piped or totally enclosed components. Odorous air is contained by the pressurized reactor and then captured and scrubbed under a collection hood before release.

Schwing Bioset - Biosolids Hauling    Schwing Bioset - Biosolids Hauling

Room to grow

The district’s biosolids plant was designed with ample space to install a second identical processing line in case the regional concept becomes a reality. “One of the most important aspects of this system is its ability to accommodate the changes a regional operation would entail,” says Ferrante. “Things like fluctuations in the percentage of solids, increases and decreases in throughput, and compatibility with biosolids from aerobic or anaerobic digestion processes without modification, are all within its design capability.

“Simply put, the district is well positioned to have its wastewater treatment needs met for the foreseeable future. After the $2 million design/build/finance contract was awarded, the district, seeing itself in a good financial position, opted to pay that cost out of pocket, rather than financing it over 20 years.”

The annual operating cost for the new system is about $130,000 a year, including chemicals and electricity. With estimated savings of $370,000 per year over landfilling, the system will pay for itself by about mid-2019.

“This was a case in which Immokalee, a small independent special district with a serious financial headache, took real initiative in getting things done,” says Ferrante. “They will be the beneficiaries of those sound decisions for decades to come.”

 

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Tags: Class 'A' Biosolids, Bioset Process, Piston Pumps, Bioset System, Wastewater Treatment, Fertilizer, Screw Press