News from Schwing Bioset

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.”

 

To view this story on TPO Magazine's website, click here.

To learn more about Schwing Bioset and the Bioset Process, click here.

 

 

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

When WWTP Says "No Tanks," Innovative Bioset Process Fills the Gap

 

Schwing Bioset Application Report 17, St. Petersburg, Florida

Written by Larry Trojak, Trojak Communications

Version also published in WE&T Magazine, November 2013

 

Pumps_Snapshot

 

Wear is the unflagging enemy of every wastewater treatment plant. Plant operators can defend against it to the best of their ability; but in the end, time will win out, resulting in breakdowns and the occasional interruption in service. To cope with such occurrences, forward-thinking plants will always have a solid contingency plan in place. For the Southwest Water Reclamation Facility (WRF) serving the Water Resources Department’s southwest sector (including St. Petersburg, FL), their contingency - designed to deal with a pair of worn, aging digester tanks - involved bypassing the tanks entirely and processing biosolids through a Bioset sludge treatment process. Doing so is not only helping them avoid an operational nightmare and additional maintenance and expense, it is allowing them to improve the by-product of that biosolids operation - all at a time when costs to land-apply their “standard” product have skyrocketed. Timing, it seems, really is everything.

 

Decades of Wear

Originally built in 1955 as a four million gallon per day (mgd) facility, the Southwest Water Reclamation Facility (WRF) was literally replaced at the same location with a 20 mgd plant in 1978. It is one of four which serve the greater St. Petersburg area: Plant #1, for the southeast section of the area which includes downtown St. Petersburg; Plant #2, to serve the northeast section of town; Plant #3, for the northwest section of the area and the beach communities; and Plant #4, for the southwest section of St. Petersburg, as well as the incorporated towns of Tierra Verde and Gulf Port. According to Ken Wise, chief plant operator for the Southwest WRF, volumes at each plant are pretty much equal.

“Plant #1 is called the Albert Whitted WRF and it’s a little smaller since there are fewer residents downtown than in other parts of the city,” he says. “But each of the other three plants are 20 mgd facilities and treat roughly the same amount of sewage. Since the upgrade in 1978 we’ve all been running an anaerobic digestion process and creating a Class B product from the biosolids. For us, that approach worked well until time caught up with us in the form of badly-worn digester tanks which were causing odor issues for an adjacent college and residential developments in the area.”

Given that two of the tanks were built in 1955 with the original plant, and the third was added with the expansion more than 35 years ago, the wear factor is not surprising. Wise says other plants in the area were also seeing failures in both the covers and in their structures as a whole.

“We hadn’t had a failure yet, but the Water Resources Department was spending a good deal of money on
upkeep with us,” says Wise. “Under normal circumstances that would have probably sufficed and bought us a few more years. However, due to changing Florida regulations surrounding the land application practices of the Class B biosolids they were producing at the time, the department started seriously looking into alternative biosolids treatment technologies hoping to avoid repairing something that was not only at the end of its life, but also might not be a fit for that new effort.”

 

Repeat Success

Bioset_Snapshot

To find that solution, the department looked at all possible alternatives, an initiative that included conducting pilot projects with various technologies at other locations in the city. One of those, at the Whitted plant, involved installing the Bioset Process sludge treatment system which uses a combination of pH and heat to stabilize the biosolids, thereby eliminating the need for digesters. 

In addition to being extremely low maintenance and operator friendly, Wise says that it had proven quick to implement and very successful there. “Ultimately the decision was made to install another system from Schwing Bioset here at Southwest,” he says. “Installation took place in July of last year (2012) and we were online by August.”

The installation, he adds, went smoothly, despite the fact that the Bioset Process had to be made to fit within the confines of an existing section of the plant rather than in a totally new site.

“The Bioset crew really worked with us to maximize use of the space we had and minimize disruption,” he says. “As a result, we probably have one of the few Bioset systems in which the reactor is raised some ten feet off the floor to fit with an existing opening. Now, sludge comes off the belt presses, is mixed with quicklime and sulfamic acid, and is pumped up into the reactor, where it spends at least 40 minutes at 135°F and achieves a pH of 12.5, before being discharged to the trailers.”

The newly-stabilized sludge is kept in the trailers on-site for 24 hours, at which point a sample is taken to ensure the pH is still in excess of 11.5 as required by Federal regulations. Since going online with the Bioset Process, Wise says the pH has never been less than 12.5.

 

Added Benefits

In addition to the elimination of virtually any odor and the complaints associated with it, it is the end product of the Bioset process - now a Class AA biosolid (the Florida equivalent of Class A-EQ) - which is the real benefit for Wise and his operation.

“In the past, our Class B material was suitable for use on sod farms and pasture lands, but because of its designation would have to be set back from any kind of food crops. By contrast, the Class AA product we get off the Bioset Process can be applied on golf courses, pastures, food crops - pretty much anywhere. In addition, because of a recent change in regulations, the other three area plants still generating the Class B biosolid are now paying an extra $300 more per trailer, while our costs dropped $100 per load. Granted, by adding the lime, the volumes are up about 10%, so the number of trailers we are shipping has increased. But even with that added into the equation, we are still saving 40 percent when compared to the Class B and have a much more usable product,” says Wise.

All of the Class AA material generated at the plant is currently either land applied at a site within an hour of the plant or sold as fertilizer to the local agricultural market. The previous Class B, by comparison, was hauled to sites more than three-hours away where it often found limited use.

 

Tanks for the Memories

The St. Petersburg WWTP has proven to be something of a case study in how to best deal with a set of unfortunate, challenging circumstances. Faced with a pair of failing digesters that were going to require a significant investment to rebuild, and which were creating odor issues for nearby residents, businesses, and students - the plant was able to solve the problems by abandoning the existing tanks and by adopting new technology in their operation. That solution from Schwing Bioset was implemented for less money than the tank rebuild project would have cost, it eliminated the odor issue, and includes the added benefit of processing cake directly to a Class AA biosolid (and gain more flexibility in the beneficial reuse of the end product), resulting in substantial net savings across the board.

"Since bringing in the Bioset System things have definitely settled down around here,” said Wise. “It’s been a great solution for us.” And, it would seem, all the issues created by the failing tanks are just fading memories.

 

To download the entire #17 application report for St. Petersburg, Florida, 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.

To view a version of this story published in WE&T Magazine, click here.

 

Tags: Class 'A' Biosolids, Bioset Process, Bioset System, Beneficial Reuse, Class AA/EQ Biosolids, Wastewater Treatment, Fertilizer

Schwing Bioset Secures Long-Term Trial with City of St. Petersburg

 

Posted on January 9, 2013

City of St. Petersburg upgrades biosolids treatment to Class AA/EQ using Schwing Bioset’s patented Bioset process. 

St. Petersburg, FL – Until recently, the city of St Petersburg, Florida’s Southwest Water Reclamation Facility relied solely on anaerobic digesters to stabilize their biosolids. However, the 20+ year old digesters had not only aged to a point of disrepair, but were beginning to cause odor complaints from the neighbors. Hence, the city felt the pressure to take corrective action quickly.

Not only would rehabilitating the existing digesters entail a sizeable expense, but in the end, the digesters would still only be producing a Class B product that needed to be hauled off to land sites. In the past this was not an issue, but the new F.A.C. 62-640 rule in Florida is going to make Class B biosolids harder to reuse in a beneficial manner.

Schwing Bioset brought in their mobile Bioset System to the St Petersburg facility in June of 2011 for a 5-day trial. Demonstrating their ability to use a natural process that eliminates pathogens by elevating pH and temperature, they proved their ability to create a Class AA/EQ product from the facility’s biosolids that would meet the 62-640 rule in Florida.

After successfully providing Class AA within 24 hours of setting up the equipment for the trial, the city engaged in an active discussion with Schwing Bioset to extend their trial to a full year. In this time, Schwing Bioset would be contracted to install all equipment, make sure operators were trained properly, and modify the city’s existing operation for a year-long period. Presently the equipment is operating successfully, the digesters are off line, the odor complaints have been eliminated, and the plant is producing Class AA/EQ biosolids that are being beneficially reused locally.

 class A for the price of class B

Tags: Bioset Process, Bioset System, Class 'AA' Biosolids, Biosolids, Wastewater Treatment

USEPA PEC Committee Grants PFRP Approval to the Bioset System

The USEPA PEC Committee Grants Nationwide PFRP Approval to Schwing Bioset and Its Class 'A' Biosolids Process known as the Bioset System

After extensive testing and research, Schwing Bioset is proud to announce that the USEPA has given nationwide approval to the Bioset Process to reduce its operating temperatures from 70°C (158°F) to 55°C (131°F) as a Process to Further Reduce Pathogens (PFRP). Operating at 55°C (131°F) results in a greater than 20% reduction in operating costs for owners of the Bioset process.

Somerset, WI 2011

After extensive testing and research, Schwing Bioset is proud to announce that the USEPA has given nationwide approval to the Bioset Process to reduce its operating temperatures from 70°C (158°F) to 55°C (131°F) as a Process to Further Reduce Pathogens (PFRP). Operating at 55°C (131°F) results in a greater than 20% reduction in operating costs for owners of the Bioset process. Prior to receiving nationwide approval, site-specific approval at one site in Texas had been granted.

The Schwing Bioset Process is a technology that continuously converts municipal biosolids into a Class A/EQ saleable product in full compliance with 40 CFR Part 503 Rule. The process mixes dewatered biosolids with calcium oxide (quicklime) and sulfamic acid (solid granular acid) and continuously pumps it into a plug flow reactor. The Schwing Bioset Process currently meets Class ‘A’ standards via pasteurization at 70°C for 30 minutes, and vector attraction reduction by maintaining an elevated pH.

At the elevated pH levels, ammonium contained within the biosolids evolves as ammonia, and the ammonia is maintained in solution with the biosolids in the pressurized plug flow reactor. Miscible contact of the ammonia with the biosolids enhances pathogen destruction to Class A/EQ standards at lower temperatures. Mixing is accomplished with Schwing Bioset’s twin-screw feeder and the blended material is pumped into the plug flow reactor with Schwing Bioset’s twin- cylinder positive displacement piston pump.

The combination of high temperature, high pH and the biocidal effects of ammonia ensure that the biosolids are pathogen free in accordance with Class A/EQ requirements. The end product is characterized as a lime enhanced soil amendment and is a valuable product for numerous land application markets. Because the Calcium in the Class A/EQ end product is readily available, soil pH adjustment occurs in less than half the time of what typical agricultural lime products require. An additional benefit of the end product is that the high percentage of organic content (35-55%) returns organic material to depleted soils.

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Tags: Class 'A' Biosolids, Piston Pumps, Bioset System, Municipal Biosolids, Class 'A' Materials, Screw Feeders, Biosolids