Winchell, Lloyd

Lloyd has been with Brown and Caldwell since 2005 and currently serves as the firm's technical lead for thermal processes. After graduating with a Master's in environmental engineering Lloyd has focused on wastewater solutions as a professional engineer. Throughout his career Lloyd has worked on wastewater solids high-temperature treatment systems, mainly incineration but also gasification and pyrolysis technologies. Lloyd has recently published six peer-reviewed articles on these technologies including the fate of PFAS through them.

Titles from this speaker

Fate of PFAS through Incineration at Wastewater Reclamation Facilities

Abstract

Introduction Per- and polyfluoroalkyl substances (PFAS) encompass a wide range of compounds, numbering in the thousands. These compounds, because of their properties, have been used in a variety of consumer and industrial products and, consequently, are widely distributed in the environment (Buck et al., 2011). Research focused on understanding the sources of PFAS in drinking water and have identified municipal wastewater reclamation facilities (WRF) as an important pathway (Clara, Scheffknecht, Scharf, Weiss, & Gans, 2008). Because PFAS are concentrated in wastewater solids (Rainey, 2019), WRFs introduce these compounds to the environment through land application of biosolids, potentially allowing PFAS to enter surface water and groundwater (Lindstrom et al., 2011). What has not been well studied is the potential for sewage sludge incinerators (SSI) to introduce PFAS to the environment or destroy it. The extent of PFAS thermal destruction (i.e., thermal degradation by-product formation or complete mineralization) is poorly understood. No published data currently exist on the fate of PFAS through an SSI, although limited information from other industries can be referenced. This paper documents the current understanding on the fate of PFAS through SSIs and the research currently underway to further our understanding. PFAS Thermal Behavior For a combustion process to achieve complete PFAS thermal destruction (mineralization), PFAS compounds would have to be driven to their thermodynamic endpoints of CO2, H2O, HF, or sulfur compounds, if present. Residence time, turbulence (mixing), and stoichiometry (the relative mixture of waste to fuel, oxygen, and other gas-phase constituents) within the flame zone impact the completeness of combustion (Lewis, 2008; Niessen, 2002). Published research and industry guidance indicate that complete destruction of PFAS requires high temperatures (Table 1) which exceeds typical temperatures in SSIs. Notably, this guidance is based on limited conceptual or laboratory-scale experiments and precedence on previous guidance established for hazardous waste incineration. The baseline research for these recommendations stems from USEPA and other international environmental agency activities. Taylor & Yamada (2003) published results of a simulated hazardous waste incineration experiment with limited air to account for non-ideal combustion conditions. Experiments showed less than 0.4% and 0.05% of the PFOS fed to the reactor were detected in the exhaust at tests conducted at 600°C and 900°C, respectively. Yamada, et al., (2005) published a similar laboratory-scale study that considered combustion of PFAS-impregnated textiles. Neither PFOA nor PICs were detected under non-ideal combustion performance. Taylor et al. (2014) found no PFOA emissions after combustion of gasified fluorotelomer-based polymers. Full-Scale Incineration Studies A few full-scale studies have been published on the fate of PFAS through incineration systems with only two considering an SSI. Loganathan et al. (2007) investigated eight PFAS through a wastewater treatment facility. PFAS were measured in dewatered solids fed to the incinerator and in the ash. No mention was made on the operating conditions or whether the bottom or fly ash was sampled. Findings indicated a significant transformation of the measured compounds (26 & 97 percent); however, some PFAS were still detected in the ash. A second study is currently underway at an SSI facility employing an fluidized bed (MacGregor, 2020). Samples were taken at all inputs and outputs of the SSI system and analyzed quantitatively for 28 PFAS. Preliminary results show that mass flows were reduced through the SSI processes for all quantitated PFAS, with the exception of 6:2 fluorotelomer sulfonate. The authors also noted that the inorganic fluoride content of the wet scrubber discharge water was over 10,000 times that of the influent flow plus the measured PFAS fed to the furnace, assuming mineralization. No other studies have been published on SSIs, but limited information can be found in literature investigating incineration in other industries. Lemieux et al. (2007) reported on the USEPA's study of feeding carpet treated with fluorotelomer products into a pilot-scale rotary kiln furnace. The emitted PFAS detected, primarily PFOA and PFHxA, did not change when feeding PFAS contaminated carpet or not. Aleksandrov et al. (2019) investigated emissions from a pilot-scale rotary kiln incinerator. No significant PFAS emissions were detected. Thermal By-Products Bench- and pilot-studies have examined decomposition of specific PFAS congeners and by-product identification; several studies documented thermal PFAS degradation by-products (Table 2). These studies show that PFAS will decompose at temperatures relevant to operating conditions of SSIs although by-product formation will be a concern. Funded Research The USEPA (2021) has recently sampled an SSI as part of a broader sampling program at a WRRF. Samples were taken from all major input and output streams of the multiple hearth for PFAS characterization. The samples are currently being analyzed for targeted, non-targeted, and total organic fluorine. Winchell et al. (2021b) provide a detailed discussion on these analytical techniques. A separate study led by Brown and Caldwell with support from the Water Research Foundation's Tailored Collaboration program will sample two SSIs, one multiple hearth and one fluidized bed. This study mirrors the USEPA from a sampling and analytical standpoint. The full-scale sample will take place during the winter and spring. Initial work has included site selection and workplan development. Including, estimating PFAS emissions at various destruction and removal efficiencies (DREs) based on targeted PFAS measured in initial dewatered cake samples. Figure 1 shows the PFAS emissions from one of the test sites remain above the reporting limits for the analytical method at relatively high DREs. This suggests specific PFAS will be detectable unless achieving high DRE, a question highly sought after by the industry. Conclusions Thermal treatment of PFAS through SSIs represents a potential wastewater solids process for destroying PFAS; although, significant questions remain regarding both the destruction efficiency and potential formation of undesirable by-products. Temperature is only one of the three key operational parameters that should be considered when assessing destruction capacity in combustion systems. The other two important factors include residence time and turbulence. A well-functioning SSI will submit PFAS to greater residence times and mixing (or turbulence) than the laboratory-scale research performed to date, further promoting PFAS destruction.

This paper was presented at the WEF Residuals and Biosolids Conference in Columbus, Ohio, May 24-27, 2022.

SpeakerWinchell, Lloyd

Presentation time

16:15:00

16:45:00

Session time

13:30:00

17:00:00

Session number03

Session locationGreater Columbus Convention Center, Columbus, Ohio

Topicincineration, PFAS, Residuals

Author(s)

L. Winchell

Author(s)L. Winchell1; J. Ross2; J. Norton3; X. Fonoll Almansa4; M. Khan5; S. Kuplicki6

Author affiliation(s)Brown and Caldwell; 1Brown and Caldwell; 2Great Lakes Water Authority; 3GLWA; 4Great Lakes Water Authority; 5Great Lakes Water Authority; 6

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2022

DOI10.2175/193864718825158449

Volume / Issue

Content sourceResiduals and Biosolids

Word count10

PFAS Assessment of a Rotary Drum Dryer

Abstract

Introduction Biosolids drying is gaining interest as a volume reduction strategy in regions where biosolids management outlets are becoming increasingly constrained due to concerns over per- and polyfluoroalkyl substances (PFAS). However, no studies as of yet have been conducted on the fate of PFAS through a thermal dryer system. Synagro partnered with Brown and Caldwell to conduct a PFAS mass balance through a centrifuge dewatering and rotary drum dryer facility to evaluate the fate of PFAS through the system and assess potential points of PFAS transfer to the environment. Methodology A three-day PFAS sampling event was conducted the week of April 17, 2023. Process samples were taken at all inputs and outputs to the system with composite sampling over a four hour period each day. An overview of the dewatering and dryer system and PFAS sampling points is provided in Figure 1. The dewatering and dryer system was operated at roughly 2,300 dry pounds of total solids per hour for the duration of the test. Gas-phase sampling was conducted by a commercial stack sampler using an OTM-45 PFAS sampling train at the stack and prior to the regenerative thermal oxidizer emissions (RTO) control device. In addition, a fourth run was conducted on the final day of the week when the dryer was down, but the scrubber was kept in operation to evaluate if PFAS were released from cooling water in the scrubber. The PFAS data was received in October 2023 and are currently being evaluated using the data quality analysis plan developed under the Brown and Caldwell lead Water Research Foundation Tailored Collaboration program project (WRF 5111). Results and Discussion PFAS sampling data is under review and will be available for detailed comparison by 2024 WEF RBC. An initial review of preliminary findings is provided in Tables 1, 2 and 3 attached with the following findings below. - Individual PFAS were transferred from biosolids to the gas phase at a transfer rate of 50% to 92% through the dryer. - No widespread trend of PFAS accumulation in the scrubber water was observed. Individual PFAS showed a modest increase from 10% to 20%. - Eighteen individual PFAS were detected in the gas phase from the dryer, prior to treatment in the RTO, - HFPO-DA and trace amounts of three PFAS were detected in the emissions from the RTO. Field QC and prior study findings indicate HFPO-DA detection may be due to contamination/interference, more work is required to verify. - More work required to refine liquid sludge analysis and develop system-wide PFAS mass balance. Conclusions This study is the first to present data demonstrating PFAS transfer from solids phase to the process air during thermal drying of biosolids. The data suggests the thermal oxidizer is capable of providing effective PFAS destruction or removal from the gas phase. More analysis will be conducted to present PFAS partitioning through the dewatering system and evaluate the aggregate PFAS mass balance through the dewatering and drying process.

This paper was presented at the WEF Residuals and Biosolids Conference, June 18-21, 2024.

Presentation time

10:45:00

11:15:00

Session time

10:45:00

11:45:00

SessionDryer

Session number15

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicDrying, PFAS

Author(s)

Ross, John

Author(s)J. Ross1, A. Seidel1, L. Winchell1, M. Wells2, D. Song 3,

Author affiliation(s)Brown and Caldwell 1; Brown and Caldwell 1; Brown and Caldwell 1; EnviroChem Services 2; Synagro Technologies, Inc.3;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159466

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count8

PFAS Data Guidelines and Implications to Fate through Thermal Processes

Abstract

Introduction Per- and polyfluoroalkyl substances (PFAS) have dominated public attention recently given their environmental contamination. PFAS resist environmental degradation and can accumulate in the urban water cycle, including wastewater systems (Winchell et al., 2021). Furthermore, various PFAS will migrate to wastewater solids (termed biosolids when stabilized) where conventional treatment technologies have little to no effect on the PFAS content of the solids (Loos et al., 2018, Gallen et al., 2018, Kim Lazcano et al., 2019). PFAS in biosolids have the potential to derail beneficial reuse via land application due to the potential impacts to groundwater, and transfer into agricultural crops (Navarro et al., 2017, Ghisi et al., 2019). Thermal treatment is the only process currently identified to reliably destroy PFAS (USEPA, 2020), but destruction efficiency must be confirmed to avoid worsening atmospheric pollution and deposition (Shafer et al., 2020). Several research initiatives have commenced to document the fate of PFAS through thermal processes, including the Water Research Foundation (WRF) Project 5111 focused on sewage sludge incinerators (SSIs). The treatment of the data when reviewing these fate studies has profound impacts on the defensible conclusions offered by researchers. This paper will present the procedures implemented for the quantifiable data from the WRF project soon to be published (Winchell et al., in review). Data Usage Guidelines Data collected as part of any research project must undergo a strict quality assurance and control program to support defensible conclusions. Data from the WRF study was subjected to a four-step assessment process (Table 1). Data were verified, validated, and qualified prior to the final assessment on usability. The research team then reviewed the quality control information and deemed reported values usable or not. This final step is critical in advancing scientific knowledge on sound information. Molar Basis Moles matter. Too often researchers sum multiple PFAS compounds on a mass basis. While convenient this can lead inappropriate assessments of process performance. For example, consider a scenario where a mixture of PFBA (MW = 214.04 g/mol) and PFHxDA (MW = 814.13 g/mol), two analytes found in the WRF study, are reported. Let's assume 100 grams of each compound entered a process, while 1 and 90 grams exit, irrespective of compound, the summed mass removal would be 55%. On a molar basis, if PFBA were the 1 gram emission the summed removal increases to 80%. Or, if PFBA were the 90 gram emission the summed removal molar removal decreases to 29%. Each researcher must consider whether the arbitrary combined mass of PFAS is critical compared to the number of molecules present. Destruction and Removal Efficiency (DRE) Researchers and regulators often characterize process pollution control in terms of DRE. Summed DRE characterizations suffer from several complications in addition to the molar discussion previously. First, current analytical capabilities can only quantify roughly 0.62% of suspected PFAS compounds (Eurofins, 2022; USEPA, 2021). Second, confident DRE assessments require reportable values of the targeted pollutant in each input and output stream. Samples absent reportable values, possible values ranging from zero to the limit of quantification, can significantly impact the significant figures in the DRE calculation. A difference between 99% and 99.9% DRE can determine regulatory compliance. Last, some input or output streams can misleadingly impact a DRE assessment as discussed in the following section. Given these complications the WRF study did not attempt to report a DRE. Instead, the average molar load of targeted PFAS were compared in the dewatered sewage sludge and stack (air emissions). From the multiple hearth furnace (MHF), only 12 µmols escape the stack while none left fluidized bed furnace (FBF), resulting in over 95% removal of PFAS, see Figure 1. Consequential Impacts of Inconsequential Streams Some input and output streams in an SSI can have impractical impacts on DRE assessments if not evaluated with scrutiny. In the WRF study, the reportable levels of PFAS in the wet scrubber supply water and drain influence DRE estimates and bias the environmental relevance of the SSI performance. Perhaps the best illustration of this paradox comes from the observation of PFHxS in the wet scrubber supply and drain, but in no other samples. The calculated DREs for each run range from 4—25%. Because the values in the wet scrubber supply slightly exceed that measured in the drain, though not statistically significant (2-tailed, α = 0.05, paired), one might attribute the entire SSI with a low DRE for this compound if applying a narrow interpretation. However, given a wet scrubber is not intended to treat PFAS contained in the supply water, the resulting DREs for PFHxS mischaracterize the performance of the thermal process. Conclusions PFAS and the data collected thereon is complicated and misuse can lead to misleading interpretations. Establishing the data base upon which confident conclusions can be supported requires application of the discussed usage guidelines. Even with a defensible dataset researchers must be wary of misleading interpretations. If properly applied, the approach discussed herein will lead to sound scientific advancement to support industry initiatives.

This paper documents the data usage approach used for the Water Research Foundation Project 5111 studying the fate of PFAS through sewage sludge incinerators. Examples are presented on the complexity and potentially misleading representations of data collected. Vastly different conclusions can be arrived at but proper treatment and interpretation of the data lead to defensible findings that advance the science of support decisions made to address the PFAS challenge.

SpeakerWinchell, Lloyd

Presentation time

15:30:00

16:00:00

Session time

15:30:00

17:00:00

SessionPFAS in Biosolids: Remove and Track it

Session number417

Session locationRoom 238

TopicBiosolids and Residuals, Intermediate Level, PFAS

Author(s)

Winchell, Lloyd, Merchant-Wells, Nicholas, Bell, Katherine, Wells, Martha

Author(s)L. Winchell1, N. Merchant-Wells2, K.Y. Bell3, M. Wells4, L. Winchell1

Author affiliation(s)1Brown and Caldwell, MN, 2Northeast Ohio Regional Sewer District, OH, 3Brown and Caldwell, CA, 4EnviroChem Services, TN

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159659

Volume / Issue

Content sourceWEFTEC

Word count11

Description: PFAS Fate in Pyrolysis System Reflecting Full-Scale Configurations: Thermal Oxidizer...

PFAS Fate in Pyrolysis System Reflecting Full-Scale Configurations: Thermal Oxidizer Impacts

Abstract

Introduction
Per- and polyfluoroalkyl substances (PFAS) are becoming an increasingly scrutinized and studied class of pollutants due to their widespread use and environmental contamination leading to federal and state health-based guidance and regulatory values. PFAS resist environmental degradation and can accumulate in the urban water cycle, including wastewater systems (Winchell et al., 2021c). Furthermore, various PFAS will migrate to wastewater solids (termed biosolids when stabilized) where conventional treatment technologies have little to no effect on the PFAS content of the solids (Hamid et al., 2016, Yu et al., 2009, Loos et al., 2018, Gallen et al., 2018, Mailler et al., 2017, Kim Lazcano et al., 2019). PFAS in biosolids have the potential to derail beneficial reuse via land application due to the potential impacts to groundwater, and transfer into agricultural crops (Lee et al., 2014, Zhang et al., 2015, Navarro et al., 2017, Ghisi et al., 2019). Thermal treatment is the only process currently identified to reliably destroy PFAS (USEPA, 2020a), but destruction efficiency must be confirmed to avoid worsening atmospheric pollution and deposition (Shafer et al., 2020). While incineration shows promise for PFAS destruction (Winchell et al., 2021a), utilities are looking to thermal treatment alternatives that do not require the same permitting rigor and generate a higher value solid residual. Pyrolysis fits these requirements.
Current Understanding
Pyrolysis systems include more than the reactor thermally processing the feedstock in a reducing atmosphere, see Figure 1. Pyrolytic reactions consume and release heat energy, with an overall heat flow generally considered zero when processing dry feedstocks (Basu, 2013). Dewatered wastewater solids require drying to evaporate water prior to treatment in the pyrolyzer. Contemporary systems recycle heat for drying and pyrolysis by processing the fuel rich off-gas from pyrolysis through a thermal oxidizer. Subsequent processes include removal and handling of the solid residual, biochar, and further cleaning of the flue gas from the thermal oxidizer. The pyrolysis systems offers several opportunities to remove and possibly destroy PFAS. Pollutant destruction and removal efficiency (DRE) in high-temperature thermal processes can generally be benchmarked by the '3 T's' (i.e., time, temperature, and turbulence). Table 1 contains key operating parameters for a recent survey of technology suppliers. The pyrolyzer can reach temperatures up to 950Â°C, depending on the goals of the solid and gas residuals, with several second residence times for the off-gas and 15-20 minutes for the solids. The thermal oxidizer conditions can likewise be tailored, but typically process the off-gas for over two seconds at over 850Â°C. PFAS destruction requirements often quoted only refer to temperature (>1,000Â°C) based on limited data sets designed for hazardous waste incineration (Winchell et al, 2021a) which can lead to premature conclusions about currently available high-temperature processes. The wastewater industry requires a better understanding on the fate of PFAS through these systems. Several studies have started looking into the fate of PFAS through pyrolysis systems processing wastewater solids. Kim et al. (2015) observed no significant change of PFAS in the biochar after pyrolysis of wastewater solids at 300 and 700Â°C in a laboratory setup. Kundu et al. (2021), however demonstrated removal of all measured PFAS species in biochar at temperatures ranging from 500 â€“ 600Â°C. Williams et al (2021) detected three PFAS of 28 evaluated in biochar at 500Â°C and none after 700Â°C. Williams et al (2021) also analyzed the off-gas stream and reported a combined mass removal efficiency of 84.4 and 95.6 percent of measured PFAS when including the levels in the biochar at the same two experimental temperatures, respectively. The body of research does not consider the impacts of the thermal oxidizer on the gas-phase outlet.
Experimental Approach
A research consortium partnered to begin evaluating the fate of PFAS through the entire pyrolysis process. The initial phase of the research considers the fate of PFAS through laboratory-scale drying, pyrolysis, and thermal oxidation systems. Collaborative funding of the partners supported construction of a laboratory-scale system at Western University's Institute for Chemicals and Fuels from Alternative Resources (ICFAR). Figure 2 shows the basic configuration of the laboratory system. Dried wastewater solids will be loaded into a 'biomass' feed hopper and metered into the mechanically stirred pyrolyzer. Off-gas can be processed through a condensing system, reflective of historical applications, or through a thermal oxidizer. The system will process roughly one kilogram per hour of dried material under conditions reflecting a currently operating full-scale system at the Silicon Valley Clean Water treatment facility in Redwood City, CA. Construction and commissioning of the laboratory system will be completed in December of 2021. PFAS sampling and analysis poses a significant challenge given the complexity, diversity, and novelty of the target substances (Winchell et al., 2021b). This research will employ the latest standardized and research methods. All streams into and out of the system will be sampled including solid and gas-phases at the laboratory scale. Using targeted, non-targeted analysis (NTA), total organic fluorine (TOF), and Fourier transform infrared spectroscopy (FTIR) this study will aim to close the PFAS mass balance across the system to the extent possible within current analytical constraints. Preliminary assessment of the donor wastewater solids and laboratory system operation suggest specific PFAS can be detected, above the method reporting limits, in the gas emissions at high DREs, see Figure 3. Furthermore, to our knowledge NTA has not been reported yet on wastewater solid pyrolysis systems. NTA identifies PFAS not currently evaluated for in the standardized USEPA Method 537 (2020b). This will help determine what 'other' PFAS are present in wastewater solids, biochar, and gas emissions.
Conclusions
This paper and presentation will provide the WEF audience a detailed summary of the current published literature on the fate of PFAS through pyrolysis systems. This summary identifies the gaps in knowledge and the proposed study takes the first step in evaluating the emissions from the system post thermal oxidation, consistent with existing configurations. An in-depth discussion on the study sampling and analytical procedures will provide the wastewater community a valuable resource on PFAS measurement. Additional value will be provided by way of the available study results.

PFAS partition to the solids generated during wastewater. Pyrolysis systems offer the potential to destroy PFAS, especially when coupled with a thermal oxidizer for off-gas treatment. Limited information can be found on the fate of PFAS through high-temperature process. This paper discusses a collaborative research effort to define PFAS behavior through a laboratory-scale pyrolyzer and thermal oxidizer validated against performance from a full-scale facility.

SpeakerWinchell, Lloyd

Presentation time

14:00:00

14:15:00

Session time

13:30:00

15:00:00

TopicIntermediate Level, Biosolids and Residuals, PFAS

Author(s)

Winchell, Lloyd

Author(s)Lloyd Winchell1; Franco Berruti2; Alexandre Miot3; John Ross4; Mary L. Romero5; Aren Hansen6

Author affiliation(s)Brown and Caldwell, St. Paul, MN1; Institute for Chemicals and Fuels from Alternative Resources, ON, Canada2; Silicon Valley Clean Water, Redwood City,CA3; Brown and Caldwell, Detroit, MI4; Brown and Caldwell, Walnut Creek, CA5; Brown and Caldwell, Walnut Creek, CA6

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2022

DOI10.2175/193864718825158645

Volume / Issue

Content sourceWEFTEC

Word count12

Pyrolyis Gas Thermal Oxidation: PFAS and Emissions Control

Abstract

Introduction Biosolids pyrolysis and gasification are gaining interest as a means to remove per- and polyfluoroalkyl substances (PFAS) from biosolids, however PFAS destruction has yet to be proven from the gas phase emissions. In 2020, the USEPA demonstrated that PFAS were removed to below reporting limits in biochar, the solid phase residual product from the Silicon Valley Clean Water (SVCW) biosolids pyrolysis system, but analytical techniques had not matured at the time for gas phase analysis (Thoma et al., 2021). Later bench scale studies showed that appreciable amounts of PFAS could be transferred from biochar to the gas phase at typical pyrolysis temperatures (500°-700°C) (McNamara et al., 2023; Williams et al., 2021). Pyrolysis gas contains an appreciable energy density and can be combusted for energy recovery and the industry has long postulated that gas-phase PFAS would be destroyed in the gas phase when combusted (Winchell et al., 2022). However, no studies had been conducted to date to demonstrate the extent of destruction. This presentation presents results from a Water Environment Federation (WEF) research study lead by Brown and Caldwell with five utility and industry partners to develop a bench-scale biosolids pyrolysis and thermal oxidation laboratory scale reactor to evaluate PFAS inputs and outputs, including flue gas emissions from the pyrolysis gas thermal oxidizer. The lab-scale reactor was created in partnership with Western University and BioForceTech, the pyrolysis system supplier for SVCW, to mimic the pyrolysis and thermal oxidation parameters from the full-scale installation. This presentation provides results from the study and lessons learned from operational issues and proposed mitigation steps for thermal oxidation at full-scale. Methodology The bench scale biosolids pyrolysis and thermal oxidation system were manufactured and commissioned by Western University over a twelve-month period starting Spring of 2022. The thermal oxidizer was configured by installing a forced air gas burner in a steel-lined combustion chamber. The burner and combustion chamber were configured with a propane pilot system that ignited the pyrolysis gas mixture, creating a self-sufficient flame when pyrolysis gas is available. The chamber was configured to provide sufficient residence time and turbulence to match the SVCW system parameters (1,000°C at two seconds). Once the system was found to meet key performance requirements the PFAS sampling event was conducted May 2023. Dried biosolids from SVCW were processed in the lab-scale biosolids pyrolysis and thermal oxidation system over three operating days for a continuous four-hour sampling campaign each operating day. Biosolids were loaded at a rate of 15 grams per minute at a solids residence time of 20 minutes and processed at a pyrolysis reactor temperature of 620°C. PFAS were analyzed in the biosolids, biochar and gas phase extracts by Eurofins. Gas-phase sampling was conducted by a commercial stack sampler, Ortech, using a modified OTM-45 PFAS sampling train. The PFAS data was received in August and September 2023 and are currently being evaluated using the data quality analysis plan developed under the Brown and Caldwell lead Water Research Foundation Tailored Collaboration program project (WRF 5111). Results and Discussion PFAS sampling data is under review and will be available for detailed comparison by 2024 WEF RBC. An initial review of preliminary findings and their comparison to a 2019 BioForceTech study is provided below. - No clear trend was observed between PFAS in the dewatered and dried biosolids. A wide range of variability in PFAS concentrations was observed indicating potential PFAS transformation in the dryer, some PFAS transfer to gas-phase, or sampling variability. - Except for PFBA at 0.7 ng/g, PFAS were below reporting limits in biochar. The reporting limit for the 2023 data was 0.4 ng/g, an order of magnitude lower than the 2-4 ng/g reporting limits available in 2019. - The loading for each PFAS to the bench-scale system ranged from 0.1 - 15 ng per second and the individual PFAS emissions rates in the flue gas ranged from 0.0001 - 0.008 ng per second, indicating individual destruction and removal efficiencies (DRE) will generally exceed 99% for PFAS in the thermal oxidizer flue gas. Conclusions This study is the first to demonstrate PFAS destruction and removal from combustion of biosolids pyrolysis gas. This data can support PFAS air permitting from biosolids pyrolysis projects under consideration by state permitting agencies such as Maine Department of Environmental Protection. While the study demonstrates the efficacy of thermal oxidation for PFAS treatment at bench scale, several lessons learned have been identified from operational issues at the full scale SVCW pyrolysis system that should be considered before widespread adoption. The main issue faced by SVCW is excessive dust from the pyrolysis reactor transferred into the combustion chamber, coating the interior of the burner and chamber. This requires a regular shutdown and cleaning cycle that takes two to three days for cooling, cleaning and reheating. This presentation will provide insights gained into dust creation and mitigation measures under consideration by SVCW and BioForceTech to improve operational uptime.

This paper was presented at the WEF Residuals and Biosolids Conference, June 18-21, 2024.

SpeakerRoss, John

Presentation time

13:30:00

14:00:00

Session time

13:30:00

15:00:00

SessionCarbonization

Session number19

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicPFAS, pyrolysis

Author(s)

Ross, John

Author(s)J. Ross1, L. Winchell1, M. Romero1, F. Kakar1, A. Miot2, J. Norton3, M. Magruder4, K. Bell1

Author affiliation(s)Brown and Caldwell 1; Brown and Caldwell 1; Brown and Caldwell 1; Brown & Caldwell 1; Silicon Valley Clean Water 2; Great Lakes Water Authority 3; Milwaukee Metropolitan Sewerage District 4; Brown and Caldwell 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159452

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count9

Pyrolysis, Gasification, and Incineration--How They Compare

Abstract

Introduction Residual solids from wastewater treatment often require further processing prior to end use, beneficially or otherwise. Historically called sewage sludge, the industry refers to these residuals as biosolids if the final product meets specific federal and state requirements (WEF 2021). Historical applications for these materials face mounting pressures from cost and decreasing site options (Collins, 2019; Slaughter, 2013; USEPA, 1994; EREF, 2021). Another pressure emerging in the industry are per- and polyfluoroalkyl substances (PFAS) (Boxall et al., 2012; Kinney et al., 2006; Navarro et al., 2018; Sepulvado et al., 2011; Walters et al., 2010; Winchell, Wells, et al., 2022). Incineration of sludge and biosolids is a widely applied and accepted technology for addressing this suite of challenges because it provides a high level of control for municipalities. However, obtaining and maintaining permits to construct and operate facilities comes at a significant cost and resource commitments in addition to relatively complex operation and maintenance requirements (WEF, 2009). These complications create an opportunity for alternative technologies to enter the industry. Pyrolysis and gasification systems offer incineration alternatives while achieving similar objectives for mass and handling cost reductions. This paper will provide the Water Environment Federation (WEF) audience with an objective comparison of incineration, pyrolysis, and gasification technologies. Basic principles, process outputs, permitting, and equipment capital costs will get covered. The information will largely reflect the recent publication by the authors in WEF's peer-reviewed Water Environment Research journal (Winchell, Ross, et al., 2022). Basic Principles The primary differentiator, outside of temperature and products, between pyrolysis, gasification, and incineration processes is the amount of oxygen introduced into the high-temperature reactor (Figure 1). Pyrolysis thermochemically converts organic feedstock to carbon-rich char and a hydrocarbon-rich off-gas in the absence of oxygen. Gasification processes further refine the char and off-gas from a pyrolysis step using a gasifying medium (such as air, oxygen, or steam). In the presence of adequate oxygen, the primary constituents of sludge and biosolids carbon, hydrogen, oxygen, nitrogen, and sulfur are combusted to thermodynamically stable end products, such is the goal of incineration. The general arrangement of the process train for pyrolysis, gasification, and incineration is similar. Figure 2 depicts the sub-processes for thermally treating sludge or biosolids and indicates the processing train is categorically similar among the three technologies, with a few exceptions. The common input to all three technologies is dewatered sludge or biosolids. Typical outputs include gas-phase emissions from the stack and solid residuals (i.e., char or ash). Table 1 summarizes the fundamental differences among these three processes. Process Outputs Regardless of the thermal technology or site-specific considerations, each process results in solid and gas-phase emissions. The solid ash or char is collected from the thermal reactor or air pollution control equipment, while gas-phase emissions are ultimately emitted to the atmosphere through the process stack. During pyrolysis and gasification, off-gas production increases as temperatures increase, while char yields decrease due to the loss of volatile components (Chen et al., 2014; Yuan et al., 2015). Nearly all carbon is combusted, and volatile components are lost during incineration, resulting in ash comprised of inorganic minerals dominated by silicon, aluminum, iron, and phosphorus oxides along with alkaline earth minerals (Li et al., 2018; Tempest, 2013). Summaries of the ash and char characteristics and air emissions, including examples of allowed levels from operating facilities, from Winchell, Ross, et al (2022) will be presented. Permitting Permitting a gasification or pyrolysis facility differs significantly from an incinerator. The Clean Water Act and Clean Air Act have sections specific to 'incineration' of 'sewage sludge.' Further, both Acts include definitions specifying combustion of the sludge or biosolids as a critical characteristic of incineration, 40 C.F.R. § 60 (USEPA, 2011). However, there are no specific references to pyrolysis, gasification, or associated thermal oxidizers, and permitting requirements are subject to a case-by-case determination (Hambrick, 2021). To date, pyrolysis and gasification facilities have avoided the 'incineration' designation (Aries Clean Technologies, 2021; USEPA, 2013, 2016) and the associated regulatory requirements. Pyrolysis and gasification systems still must undergo an air permitting process similar to that required for an incinerator as outlined in WEF (2009). In general, the current regulatory framework provides pyrolysis and gasification systems a distinct advantage over sewage sludge incinerators if they can continue avoiding the 'incineration' designation. Equipment Capital Costs Several high-temperature equipment suppliers provided planning level capital costs for a single train of equipment from the point of dewatered sludge or biosolids delivery to the stack, including a handling system for residual solids. Figure 3 displays the cost information in cost curve fashion. The pyrolysis and gasification technologies offer a cost-benefit at lower processing capacities but become comparable to incineration at the 110 dry tonnes/day capacity. Given the cost advantages of pyrolysis and gasification technologies in small to mid-size treatment facilities, this is likely where these technologies will enter the wastewater market. Conclusions Primary advantages of pyrolysis and gasification systems versus a contemporary incinerator identified include operating characteristics, equipment sizing, air emissions, emissions regulations, potential char applications, and equipment costs. These advantages need to be weighed against the added complexity of equipment required for these processes. These advantages and disadvantages will be discussed and detailed in the full paper. Altogether, pyrolysis and gasification show promise as alternatives to incineration for some facilities, particularly small to mid-sized facilities, and the current and contracted-to-build installations will, over time, provide valuable information on real-world operating and maintenance requirements.

This paper was presented at the WEF/IWA Residuals and Biosolids Conference, May 16-19, 2023.

SpeakerWinchell, Lloyd

Presentation time

13:30:00

14:00:00

Session time

13:30:00

16:45:00

SessionSession 16: Advances and Innovations in Thermal Processes I

Session number16

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicResearch & Innovations

Author(s)

L. Winchell

Author(s)L. Winchell1, J. Ross2, D. Brose3, T. Bremm Pluth4, X. Fonoll Almansa5, J. Norton6,

Author affiliation(s)Brown and Caldwell1; Metropolitan Water Reclamation District of Greater Chicago2; Great Lakes Water Authority3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158826

Volume / Issue

Content sourceResiduals and Biosolids

Word count7

Description: Thermal Treatment of PFAS with Gasification, Pyrolysis, Incineration, and...

Thermal Treatment of PFAS with Gasification, Pyrolysis, Incineration, and Supercritical Water Oxidation (SCWO) - What is the Current Status?

Abstract

PFAS has become a major concern in wastewater treatment. Thermal processes offer an opportunity to treat PFAS using different technologies such as gasification, pyrolysis, incineration, thermal oxidation, and supercritical water oxidation (SCWO). There have been several promising pilot and bench scale studies resulting in high removal efficiencies of PFAS from biosolids. This technical paper presents and compares the results of the most recent studies on PFAS treatment using thermal technologies. Pyrolysis, gasification, and incineration technologies have been compared in a technical paper by Winchell (2023). Based on the results, pyrolysis and gasification were shown to be promising alternate technologies to incineration in terms of lower capital cost at lower feed rates, relaxed emission limits compared to incineration requiring less equipment for the air pollution control system, and the potential use of char, which is a by-product of pyrolysis and gasification process. A study by Williams (2023) confirmed that pyrolysis had the potential to reduce or eliminate the measurable concentration of PFAS in biochar. PFAS emissions testing was also performed at the stack outlet of the wastewater solids gasification and thermal oxidation demonstration scale installation in Loganholme, Australia (Loganholme City Council, 2021). Gasification systems operate similar to pyrolysis units except some oxygen gets introduced to the thermal reactor to further refine the off-gas and biochar products. The thermal oxidizer operated at a two seconds residence time at 800-850°C. In this case, the total mass of 28 PFAS in the outlet measured 47 ng/Nm3 over a 100-hour sample event. This emission level translated to an over 94% PFAS treatment efficiency across the thermal process train. Another study by 374Water (Sudhakar, 2023) indicated that SCWO technology could achieve more than 99.99% PFSA removal efficiency using proprietary AirSCWOTM process to treat PFAS from lime stabilized PFAS laden sludge. A lab scale study by Veolia (Mocock, 2023) confirmed that almost complete destruction of PFAS was possible using thermal oxidation at a combustion temperature of 1150°C at two different gas residence times (two and four seconds). Higher gas residence time (four seconds) at the same combustion temperature (1150°C) resulted in lower PFOA and PFOS air emissions during the lab scale tests. Bench and pilot scale studies by Laub (2023) indicated that pyrolyzed biosolids did not have any measurable levels of PFAS. Results of these studies have been presented at conferences such as WEF/IWA Residuals and Biosolids and WEFTEC in 2023. In this technical paper, PFAS test results from the most recent pilot and bench scale studies are being presented and compared to each other to determine the current status of PFAS treatment efficiencies for gasification, pyrolysis, thermal oxidation, and SCWO.

This paper was presented at the WEF Residuals and Biosolids Conference, June 18-21, 2024.

Presentation time

10:45:00

11:45:00

Session time

10:45:00

11:45:00

SessionDryer

Session number15

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicGasification, incineration, PFAS

Author(s)

Jordan, Gwyneth

Author(s)G. Jordan1, L. Takmaz1, L. Winchell2

Author affiliation(s)Veolia Water Technologies & Solutions 1; Veolia 1; Brown and Caldwell 2;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159477

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count20

Update - NEORSD Southerly WWTC Biosolids Combustion Optimization

Abstract

Problem Since the startup of the three fluidized bed incinerators (FBIs) at the Northeast Ohio Regional Sewer District (NEORSD) Southerly Wastewater Treatment Center (Southerly WWTC) in 2014 greater than expected auxiliary fuel, that is natural gas, usage has been observed. The original FBI design assumed no auxiliary fuel would be necessary during typical operations. This abstract updates the paper submitted for the 2020 RBC, which was unfortunately cancelled due to the pandemic, with additional data obtained during the interim. Background The NEORSD owns and operates three FBIs at the Southerly WWTC, each design to process 100 dry tons per day (dtpd) at 28 percent solids and 68 percent volatile solids. The FBIs are fed dewatered sludge cake consisting of primary and waste activated sludges generated at the Southerly WWTC. Sludge from the Easterly WWTC managed by NEORSD, discharges into the headworks at the Southerly WWTC for ultimate processing by the FBIs. Typically, FBIs do not require auxiliary fuel when operated near the design condition. Auxiliary fuel is required during startup and sometimes during shutdown operations. Continued use of auxiliary fuel throughout all operations indicates the system is not operating as designed. Objective This study evaluated the existing conditions the FBIs operate under to determine which parameters might be adjusted for more efficient operation. NEORSD can then adjust, as possible, to reduce auxiliary fuel use. Historical Operation Evaluation NEORSD originally provided one year of hourly (average) data from April 2016 to March 2017, see Table 1 for the operational averages. The data was evaluated to determine which parameters impact autogenous operation. The screened parameter set included the following six which were likely to have the greatest impact on autogenous operation. Sludge feed Sludge percent solids Sludge percent volatiles Windbox temperature (preheated air from heat exchanger) Bed temperature Fluidizing airflow All these parameters statistically correlated with autogenous operations at specific levels per the t-test results in Figure 1. So, BC further evaluated this list using NEORSD's existing operating strategy as a guideline. In the end, BC determined the sludge feed rate was the most readily adjustable parameter to achieve more reliable autogenous operation. The sludge feed provides all the heat, when operated close to design values, to heat the combustion air and evaporate the water from the sludge without natural gas addition. When averaging all three FBIs the average sludge feed rate is 1.2 wet tons per hour (wtph) higher during autogenous conditions. It should be noted that the average sludge feed rate, during these autogenous conditions, was roughly 64 percent of the incinerator capacity (13.9 wet tons per hour at 30 percent total solids [TS]). The data suggests that operating the FBIs at higher feed rates will result in autogenous conditions more often. Operational Alternatives Two distinct operational changes could increase the sludge feed rate per FBI. Each option increases the number of thermal cycles, that is the frequency the system goes from operating temperatures to a significantly cooler level. Revised Operations — Option 1 - The first option utilizes storage capacity to provide consistent incinerator operations. Each storage tank holds approximately 1.5 days' solids processing capacity of one incinerator. There are three storage tanks available for operational storage with a fourth one for emergency storage. This option uses one sludge storage tank with one FBI to handle the solids with excess flowing into a second sludge storage tank. When the second sludge storage tank becomes half full and climbing a second FBI can be brought on line to help deplete the incoming and stored solids until one FBI can again handle the solids production. This option includes some concerns about placing additional thermal cycles on the equipment. Revised Operations - Option 2 - The second option operates two FBIs at a higher capacity. This is accomplished by placing one of the operating FBIs in hot standby mode for 6 to 8 hours every day. Though the FBI internals would likely see a relatively small thermal cycle, downstream equipment will undergo a larger cycle or temperature range. Option 2 would also likely not yield the same natural gas savings due to heating if the standby FBI required intermittent heating during downtime. Revised Operation Implementation An industry survey was conducted to better understand thermal cycling on sewage sludge incineration systems and impacts on equipment. Based on the survey Option 1 would likely result in less thermal cycle impacts due to relative infrequency compared to Option 2. Furthermore, discussions with the key equipment supplier (primary heat exchanger and waste heat boiler) indicated the equipment was designed for far more thermal cycles than practical over the anticipated service life of the equipment. After reviewing the two options NEORSD selected and began planning to implement Option 1. NEORSD operates three sludge storage tanks, two are normally used with a third for peak demands. At an assumed 5 percent solids concentration each tank holds roughly 230 dry tons of solids. Each cycle from 1 FBI to 2 FBIs and then back to 1 FBI should take approximately 30 to 40 days, depending on the sludge generation rate, the sludge incineration rate, and the sludge solids concentration achieved in thickening and storage. Based on this approach the FBI sludge feed rate will exceed 80 percent of the design capacity, greatly increasing the chances for autogenous operation. NEORSD conducted multiple full-scale trails, with a month-long campaign in April of 2019 providing the most representative operations of the selected option. Other trials in May 2019, September/October 2019, and August 2020 resulted in shorter durations and experienced other complications resulting in higher energy consumption. Table 2 presents the comparison between the trials and historical costs spanning 2016 through 2018. Costs in the table represent annual values. The trial values were projected to annual operations for comparison. The results of the trials indicate energy and economic savings will result from the revised operating strategy. The April 2019 trial most represents the anticipated revised operating strategy and would result in an annual savings of $390,000. Conclusions This study initially investigated the alternatives to minimize the use of auxiliary fuel during normal operations. This effort identified that recommended increasing the sludge feed rate reduces auxiliary fuel demand and presented two options to achieve a higher FBI throughput. NEORSD opted to manage the sludge in the SSTs to operate the FBIs at a higher sludge feed rate which requires alternating between one and two FBIs in service. The recent April 2019 full-scale trial showed significant energy reductions from the revised operating strategy. Based on this effort NEORSD will continue to pursue operating in the revised manner full time. NEORSD will also continue to closely monitor equipment condition to prevent unplanned outages and whether the slight increase in thermal cycles have any effect. Status NEORSD continues to test the revised operating strategy to verify the operational savings and gain experience. Ultimately the strategy will be implemented as the standard operating procedure.

The following conference paper was presented at Residuals and Biosolids 2021: A Virtual Event, May 11-13, 2021.

SpeakerWinchell, Lloyd

Presentation time

11:15:00

11:30:00

Session time

11:00:00

11:45:00

SessionThermal Process Optimization

Session number6

Session locationSimu-Live

TopicEnergy recovery, Operations And Maintenance, Thermal Processes