News from Schwing Bioset

Membrane Bioreactors Increase Effluent Quality at Hotel and Casino

 

Written by Surya Pidaparti

 

The Santa Ynez Band of Chumash Indians operates a hotel and casino in Chumash, California. The sewage from the facilities used to be treated by a conventional sequencing batch reactor (SBR) and sand filtration. As the hotel and its vicinity expanded, the existing SBR was not able to treat the increased flow, which was the major driving force for upgrading the facility. As the area is a high drought zone, a requirement of any permit for expanding the hotel would require water reuse.

Two options were selected to evaluate for the wastewater treatment expansion project – an expansion of the existing SBR alongside the existing and abandoning the SBR in favor of a Membrane Bioreactor (MBR) system. An extensive engineering evaluation showed that the MBR system had a total construction cost of $3.3 million versus a cost of $5.3 million for the SBR.

Econity MBR’s were selected, as offered by Schwing Bioset, for not only their performance, but their flexibility in design. With a cartridge and cassette configuration, maintaining the membranes becomes a simple exercise. The MBR system was built using two containers to minimize disruptions to current plant operations and to fit in the limited site space available. The facility was commissioned in January of 2016.

With the improvements, there has been a significant increase in the facility’s capacity all while showing that that the effluent quality, measured in turbidity (0.05 – 0.2 NTU) vastly exceeds California Title 22 requirements for reuse water (< 1NTU).

To learn more about Schwing Bioset’s MBR systems, contact Surya at spidaparti@schwingbioset.com or visit our website here.

 

Schwing Bioset Membrane Bioreactors  Schwing Bioset Membrane Bioreactors

 

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Tags: Wastewater Treatment, Membrane Bioreactor

Recovering a Valuable Nutrient From the Wastewater Stream

 

Published in TPO Magazine, August 2019

 

Phosphate recovery technology offered by Schwing Bioset can be tailored to meet each facility’s specific operating challenges

 

Resource recovery is a major trend in wastewater treatment — to the task of cleaning water, facility teams are adding the capture of energy and nutrients.

One increasingly popular type of technology is the capture of phosphorus as struvite, which has market value as a fertilizer additive. One entry in that sector is Schwing Bioset, which offers a phosphate and nitrogen recovery technology under license from Belgium-based NuReSys.

The offering is unique in that it is not necessarily designed to extract revenue from nutrient capture, although that option is available. The process is designed to be tailored to each facility’s objectives in dealing with phosphate-related issues.

Besides nutrient recovery, the process has the benefits of preventing buildup of struvite scale in treatment equipment and improving dewaterability in biosolids. Wim Moerman, chief technology officer for NuReSys, and Chuck Wanstrom, director of new business development with Schwing Bioset, talked about the technology in an interview with Treatment Plant Operator.

 

Click here to read the full interview.

 

Nutrient Management Plant

 

To learn more about Schwing Bioset’s Nutrient Management solutions, visit our website here or contact your Region’s Representative.

 

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Tags: Wastewater Treatment, Struvite Recovery, Nutrient Recovery, Phosphorus Removal, Nutrient Harvesting

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

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

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.”

Columbus_Southerly_odor_hood.jpg

 

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

Orlando Selects Schwing Bioset over Anaerobic Digestion for Class AA Biosolids

 

Authored by Tom Welch, Southeast Sales Manager for Schwing Bioset, Inc., and Vic Godlewski Jr., PE, Wastewater Division Manager, City of Orlando

May10, 2016

The City of Orlando has been working for several years to move away from Class B land application of Biosolids.  The City explored use of an experimental technology that would almost fully oxidize Biosolids leaving very little residuals for disposal.  While investigating this experimental technology, the City delayed renovations to the anaerobic digestion systems at their Conserv II Water Reclamation Facility (WRF).  Ultimately it was determined that the oxidation technology was not yet commercially viable, at which point they could no longer postpone biosolids treatment improvements.  Orlando engaged the services of a Consulting Engineer to evaluate the digesters and prepare project cost estimates from simple renovation to Class A TPAD with sidestream treatment and combined heat and power.  The estimated project costs were over $40 million and climbing.  Since Orlando believes that the market is going to deliver better options than anaerobic digestion in the future, they began to look for interim options that could be implemented relatively quickly at low capital cost investment; improve their Biosolids treatment, potentially eliminate the need for land application, and not substantially increase O&M costs.  That was a tall order!

The City 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 St. Petersburg as well as other locations 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.

Schwing Bioset offered a Design Build approach that was very appealing.  However, due to the City’s procurement constraints this path was not available. To speed up project delivery the Bioset process equipment was purchased directly by the City and installation was competitively bid.

Orlando_Conserv_II_image_3.jpg

Orlando_Conserv_II_image_2.jpg

As shown in the photos above, the Bioset equipment is currently being installed at the Conserv II facility and is scheduled for startup in the summer of 2016.  Schwing Bioset has a sister company, Biosolids Distribution Services (BDS), that manages Class AA Fertilizer Grade Biosolids in the state of Florida.  They have marketed in excess of one-million wet tons of Class AA fertilizer in the state of Florida over the last 10 years.  BDS will be managing the Biosolids produced at the Orlando Conserv II facility when the Bioset process becomes operational.

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

 

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Tags: Bioset Process, Class 'AA' Biosolids, Wastewater Treatment, Biosolids Distribution Services, Commercial Fertilizer

Bioset Demo Confirms Direction for New Class A Biosolids Equipment at Russellville WWTP

 

Written by Lance Bartlett, Utility Engineering Manager for City Corporation and Tom Welch, Southeast Regional Sales Manager for Schwing Bioset, Inc.

April 25, 2016

 

In early 2015, City Corporation, the commission established by the City of Russellville to operate the municipal water system, completed a construction project to abandon existing fixed film treatment facilities and convert the wastewater treatment plant to a denitrifying activated sludge facility.  Activated sludge technologies produce more sludge than fixed film and initial calculations predicted an increase of 6 to 7 times the current production rate when operated at the design capacity of the facility.

City Corporation had processed sludge through aging aerobic digesters and produced a Class B biosolid under 40 CFR 503 that was then dewatered and land applied to three nearby fields.  Two of the three permitted fields were no longer available, leaving only 49 acres for use.  The increase of sludge production was predicted to require around 160 acres.

The expected increase in sludge production and lack of land available for land application prompted staff to explore options.  The alternatives explored included composting, additional aerobic digesters, dryers, and the Bioset process from Schwing Bioset, Inc. (SBI). The Bioset process was selected for piloting in February and March of 2015 due to its low cost, simple operation, and the high quality Class A product that it produces.  The lone concern was with respect to the increase in volume due to the addition of chemicals, and staff wanted to get the new process up and running to obtain empirical data on sludge volume.  The engineering firm performing the preliminary study had built in a large contingency due to not being familiar with the Bioset technology and the uncertainty in sludge volume, thus raising concerns that the Bioset technology would be the proper process for the future of the Russellville WWTP.  Ultimately the volumetric increase was less than 10%, and with the Class A designation the number of outlets and demand for the material exceeds production rates.

Russellville_Bioset_3.jpg Russellville WWTP_Bioset Process_Schwing Bioset

Following that successful pilot test, in April of 2015, Schwing Bioset agreed to continue to lease the pilot machine under a monthly contract basis for the sludge handling process.  By the fall, City Corporation had a good feel for their solids production and had a great experience with the Bioset full scale pilot equipment.  Given the years of struggling with the Class B sludge process, management and staff were very pleased with the Class A process and end product and the thought of returning to a Class B process was taken off the table. With all the uncertainty taken out of the equation, staff was ready to make a decision and chose to move forward with a permanent Bioset installation.  City Corporation and Schwing Bioset continue to operate under a contract that allows City Corporation to operate the pilot unit until the permanent unit is installed and operational.  This arrangement allows City Corporation to manage their sludge and operate the plant in accordance with the design parameters, keeping the facility in compliance with the ADEQ, which otherwise would not be possible.  The new facility is anticipated to be operational in mid-October 2016.  The current digester will only be used as a sludge holding tank, thus reducing the power consumption needed for complete aerobic digestion to meet Class B standards, and allowing just WAS sludge to be converted to Class A EQ fertilizer through the Bioset process.

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

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Tags: Bioset Process, Class AA/EQ Biosolids, Wastewater Treatment, Lime Stabilization, Bioset Demo

Phosphorus Removal and Nutrient Harvesting Continuing Education

 

Written by Eric Wanstrom, March 22, 2016

Schwing Bioset is pleased to announce the Schwing Bioset Phosphorus Removal and Nutrient Harvesting paper has received accreditation and official approval for continuing education credits in New York State.  

Schwing Bioset’s Nutrient recovery system recovers Ortho Phosphate and Ammonia Nitrogen from wastewater while offering great benefits to the treatment plant, not only by significantly reducing phosphorus in the waste stream, but also preventing unwanted scaling and accumulations, and creating a valuable end product.  The phosphorus forms a stable Struvite crystal that can be marketed and sold for beneficial reuse, thus keeping excess phosphorus out of the local waterways and helping close the phosphorus recycling loop.   

Engineers and operators can receive one (1) hour of CEU credits for attending a presentation on these topics.  Please contact us to schedule the presentation for your office or plant.

You can learn more about the NuReSys Nutrient Harvesting Process at the links below.

http://www.schwingbioset.com/struvite-recovery

http://www.schwingbioset.com/news/topic/nutrient-recovery

 

For questions or comments, please email this blogs author, Eric Wanstrom, call 715.247.3433, and/or visit our website.

 

Schwing Bioset Nutrient Harvesting

 

Tags: Wastewater Treatment, Continuing Education, Struvite Recovery, Phosphorus Removal, Nutrient Harvesting

Heat Integration – Opportunities and Concerns

 

Written by Joe Scholl, February 11, 2016

The word “heat” may be defined as the amount of energy that is transferred from one system to another, typically via a temperature differential or “gradient,” and the amount of heat something possesses may be stated in terms of British Thermal Units (BTU), Joules (J), calories (cal), etc. (as compared to reference temperature or datum state).  Measured over time, heat becomes energy that is used to accomplish tasks, and that energy may be measured in BTU/hr, J/sec, etc.  There is a definite cost to energy usage, as evidenced by any plant’s energy utility bill.  As such, there is a high emphasis nowadays in energy re-use (“heat integration”) via applying “waste” heat from one process to another process needing energy.  While many such heat/energy integration techniques may be easily accomplished, there may, under certain circumstances, be limitations to the extent such energy re-utilization efforts may be accomplished.

Many municipal wastewater treatment plants (WWTP’s) are utilizing anaerobic digestion systems and these processes may produce digester gas or “biogas” (chiefly methane and carbon dioxide with other trace chemical constituents and/or contaminants).  The biogas produced may be used by a variety of means, such as for maintaining heated conditions in the digester units and/or in gas engines that drive generators to produce electricity in a combined heat and power cycle (CHP).  These CHP processes generally produce two “waste” heat streams by which heat may be extracted and re-utilized (i.e. “integrated”) in another process.  These two streams are the exhaust (or “stack”) gas from the biogas combustion process itself and a hot water stream (typically a water/glycol mixture) or steam produced from using cooling water to maintain reasonable CHP engine temperatures. 

The extent to which these particular waste heat sources can be utilized depends on many factors, including the costs associated with purchasing, installing, and operating the heat recovery equipment.  With respect to utilizing a waste heat source in a sludge thermal drying operation, some of these factors may include:

  • How close to the drying system is the heat source? Specifically, what are the fluid movement costs from point A to point B, in terms of liquid pumping or gas handling requirements and how does this impact the overall heat integration strategy?  
  • What is the additional capital expenditure (“Capex”) requirement to install insulated piping or ducting from the source to the drying system and are these Capex requirements so high that the payback to incorporate the waste heat into the drying system result in an unreasonably long payback period? 
  • Are long-term corrosion issues a concern, such as materials of selection for digester gas piping, stack gas ducting, etc. (especially if “acid gases” condense-out of the gas stream upon cooling, leading to corrosive conditions within the piping, ducting, or heat transfer equipment) and, if so, what is their Capex impact, as well operating expense (“Opex”) impact (e.g. will long-term corrosion issues require long-term maintenance expenses)? 
  • How much heat will the waste heat stream lose from point A to B and will this heat loss drive the heat recovery economics toward an unfavorable overall result? This point is particularly important if the waste heat stream is steam, where the latent (or condensing/phase change) heat of the steam is the primary (or desirable) heat transfer mechanism.  For example, if the waste steam loses sufficient energy in transit from its source to the drying system, will the steam lose so much heat that it condenses to liquid form, thereby “robbing” the heat integration scheme of the steam’s latent/condensing heat prior to the drying system (noting that the latent/condensing heat of steam is significantly higher than the specific heat capacity of either the steam or liquid forms)?

In general, there are many possibilities for incorporating waste heat into a thermal drying process.  However, the costs (in terms of Capex and Opex considerations) to incorporate the heat integration step must also be considered to determine whether doing so is practical. 

To learn more about waste heat integration strategies and our Fluid Bed Drying Technology, please contact a Schwing Bioset Regional Sales Manager by calling 715-247-3433, email us, and/or visit our website here.

 

Below is just one example of numerous heat recovery possibilities.

Schwing Bioset Stack Gas Heat Integration Schematic

  

Tags: Fluid Bed Drying, Wastewater Treatment, Heat Integration, Energy Re-Use, Heat Recovery