Orr, Jon

Jon Orr is Product Manager, for the Biosolids Bioenergy team at Veolia Water Technologies / Kruger business unit, based in Cary, NC. He holds a BS degree in chemical engineering from Cornell University, and an MBA from the University of Houston. He has 15 years of work experience in wastewater residuals and sludge treatment technologies, and over 25 years in project operations management, product technology development.

Titles from this speaker

Description: Lab-scale Evaluation of PFAS Decomposition and Flue Gas Qualities from Biosolids...

Lab-scale Evaluation of PFAS Decomposition and Flue Gas Qualities from Biosolids Incineration Process

Abstract

The presence of perfluorinated alkylated substances (PFAS) in municipal wastewater sludge/biosolids is a growing concern for facilities that rely on land application as the main disposal method. Thermal combustion is considered a viable solution to decompose the PFAS compounds in the biosolids. Two bench scale combustion studies were conducted at a combustion temperature of 1150oC with two gas residence times (GRT) of 2 and 4 seconds, respectively. The ash residuals generated from the two studies meet the PFAS requirements for biosolids land application imposed by the Stage of Michigan. The estimated levels of PFAS constituents as measured in the flue gas indicates the potential of the combustion technology to meet the air emission requirements at 70 ng/m3 for PFOA and PFOS also imposed by the State of Michigan. The GST of 4 seconds at a combustion temperature of 1,150oC improved the decomposition of the PFAS compounds measured and lowered the air emission for PFOA and PFOS, compared to the 2 seconds GRT at the same temperature.

The presence of perfluorinated alkylated substances (PFAS) in municipal wastewater sludge/biosolids is a growing concern for facilities that rely on land application as the primary disposal method. Thermal combustion is considered a viable solution to decompose the targeted PFAS compounds in biosolids. The decomposition results for targeted PFAS analytes from two combustion studies conducted at a combustion temperature of 1150 deg C at gas residence times of 2 and 4 seconds are presented.

SpeakerZhao, Hong

Presentation time

13:30:00

13:50:00

Session time

13:30:00

15:00:00

SessionBehavior of Emerging Contaminants in Thermal Treatment Processes

Session locationRoom S503 - Level 5

TopicIntermediate Level, Microconstituents and Contaminants of Emerging Concern (Non-PFAS), PFAS

Author(s)

Zhao, Hong

Author(s)H. Zhao 1; J. Orr 2 ; J. Mocock 3; T. Yamada 4; M. Kahandawala 5; A. Erdogan 1; S. Chalivendra 6;

Author affiliation(s)Veolia Water Technologies 1; Veolia Water Technologies 2 ; Veolia Water Technologies 3; University of Dayton Research Institute 4; University of Dayton Research Institute 5; Veolia Water Technologies 1; University of Dayton Research Institute 6;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159081

Volume / Issue

Content sourceWEFTEC

Word count14

Lab-scale Evaluation of PFAS Decomposition and Flue Gas Qualities from Biosolids Incineration Process

Abstract

Introduction In order to better understand the fate and transport of PFAS compounds in wastewater sludge undergoing thermal combustion, a bench-scale system, that mimics a full-scale biosolids incineration, was constructed. Two batch studies were conducted with the system in 2020 and 2021 to investigate: 1) the decomposition and removal efficiency (DRE) of the PFAS in biosolids; 2) the residual PFAS concentrations in the ash, 3) the PFAS concentrations in the flue gas, and 4) the effect of operating parameters on the performance. The operating parameters evaluated were combustion temperature and gas residence time. Methods The two studies are identified as the 2020 and 2021 studies in this abstract. The feed sludge samples used for the two studies were obtained from two municipal wastewater treatment plants. While the same schematic of the bench scale testing system (e.g., a silica quartz tube) was used for the two studies, the sizes of the tubes were different. For example, the length and outside diameter (OD) were 54.0 inches and 2.0 inches for the 2020 study. In order to increase the gas residence time (GRT), the 2021 study used a larger tube with a length of 78.0 inches and an OD of 4.0 inches. As shown in Figure 1, the sludge sample was fed into the reactor tube by a sample boat. The average sludge sample residence time (SRT) in the reactor tube was approximately 5 min for both studies. The reactor tube consisted of three zones. The temperatures over Zone 2 (effective length) of the reactor tube were set 1,150 °C (+1 °C, -51 °C) for the 2020 study and 1,150 °C (+21 °C, -58 °C) for the 2021 study. Air was injected into the reactor tube from the feed end at a constant rate to achieve a pre-set GRT. The GRT was defined based on the volume over the effective length and the actual airflow at 1,150oC. The combustion flue gas was collected by the impingers on the exhaust end of the reactor tube. The impinger setup consisted of four impingers in series. Each 2-L impinger was filled with DI water at a volume of 1.5 L. The above operating conditions are summarized in Table 1. The 2020 study consisted of three triplet tests. Each triplet test generated one impinger sample. The residual ash from the triplet tests was combined to have one ash sample because the amount of ash generated from one triplet test was not enough for performing lab analysis. The 2021 study also consisted of three triplet tests. Due to the large amount of samples used, each triplet from the 2021 study generated one impinger sample and one ash sample. All samples were analyzed for PFAS by Eurofins/TestAmerica with 12-targeted analytes for the 2020 study and 36-targeted analytes for the 2021 study. Fluoride was analyzed for all the impinger samples by the same laboratory for PFAS. Test Results For conciseness, only the major PFAS compounds such as PFOA, PFOS and Total PFAS are presented in Table 2. As shown, total PFAS concentration in the raw sludge was 118 ng/g and 59 ng/g for the 2020 and 2021 studies, respectively. Due to the low total PFAS concentrations, the raw samples were spiked with PFOA, PFHxS, PFHps and PFOS to a total PPFAS level at 31,292 ng/g and 5,893,800 ng/g for the 2020 and 2021 studies, respectively. The purpose of the spiking was to study the PFAS decomposition capability by the combustion process. As shown in Table 2, the spiking level for the 2021 study was 188 times higher than that of the 2020 study. The PFAS level in the ash sample from the 2020 study was much lower than that of the 2021 study (0.32 ng/g versus 11.0 ng/g). This may be due to the large difference in the feed PFAS spiking. The total PFAS level in the ash sample from the 2021 study was 26.1 ng/g at maximum (i.e., 26.1 µg/kg) and 11.0 ng/g on average under the total spiked PFAS concentration of about 5,900,000 ng/g. These residual PFAS results indicate that the ash after the thermal combustion process can meet the PFOS permit level (50 µg/kg) for land application imposed by the State of Michigan. PFAS Decomposition Efficiency - As shown in the schematic (Figure 1), the impinger sampling system was designed to catch the PFAS in the flue gas from the reactor tube, which represents the flue gas coming directly out of the furnace but before the air pollution control (APC) equipment for full scale incineration projects. As mentioned in the experimental setup section, the impinger samples were analyzed for fluoride. The fluorine balance was conducted based on the measured PFAS level in the spiked sludge samples and the measured fluoride concentration in the impinger samples. A fluorine balance ranging from 78% to 88% was achieved in the combustion tests. The fluorine balance above 80% indicates a reasonably good mass balance on the combustion system, thus using total PFAS balance around the combustion reactor to calculate the decomposition efficiency is valid. The mass balance results and the decomposition efficiencies from the two studies are presented in Table 3. As shown, the PFAS mass in the feed was about 3,000 times more in the 2021 study than the 2020 study due to that the higher spiking concentration and larger sample mass were used for the 2021 study. However, the total recovered PFAS mass based on the impinger and ash samples were not significantly different between the two studies. The average total PFAS recovery by the impinger and the ash samples is 207.9 ng and 243.8 ng for the 2020 and 2021 studies, respectively. Therefore, the PFAS mass destroyed in the 2021 study was about 3,000 times that of the 2020 study, which was reflected by the PFAS decomposition efficiency. As shown, the PFAS decomposition efficiency based on total PFAS (sum of the 36 analysts) was at a level of 99.9999% (6 logs) for the 2021 study and 99.67% (close to 3 logs) for the 2020 study, on average. The major difference in operating conditions between the two studies was the gas residence times - 2 seconds for the 2020 study and 4 seconds for the 2021 study. The two tests were run at the same combustion temperature of 1,150oC. Therefore, it was believed that doubling the gas residence time from 2 s to 4 s improved the PFAS decomposition efficiency. Estimated PFAS Level in Flue Gas - The PFOA, PFOS, and 6:2 FTS levels in the flue gas were estimated based on their mass caught by the impinger divided by the total air volume (in m3 at STP) supplied during each triplet batch. The estimates represent the flue gas PFAS levels at the point before the air pollution control (APC) equipment for full-scale systems. The estimated flue gas PFOA, PFOS, and 6:2 FTS concentrations are summarized in Table 4. Statistical analysis indicates that even though the variability of concentrations within each triplet batch is large, the average concentrations of PFOA and PFOS in the flue gas obtained from each study are significantly different. The average flue gas PFOA and PFOS levels for the 2020 study were about 132.3 ng/m3 and 152.7 ng/m3, respectively. However, the average levels of PFOA and PFOS for the 2021 study were about 60.8 ng/m3 and 59.4 ng/m3, respectively, which are below the permit levels of 70 ng/m3 imposed by the State of Michigan for the air emission. It must be noted that the PFOA and PFOS levels in the flue gas estimated by the two studies represent the concentration before the APC equipment. The results from the 2021 study suggest that the air combustion operated at 1150oC and 4 seconds GRT can meet the emission requirements. Conclusions This bench scale study demonstrates that thermal combustion can be effectively and efficiently utilized to achieve near complete PFAS decomposition in the biosolids. The ash residuals generated from the two studies conducted at a combustion temperature of 1150oC and GRT of 2 and 4 seconds meet the PFAS requirements for biosolids land application. The estimated PFAS level in the flue gas indicates the potential of the combustion technology to meet the air emission requirements at 70 ng/m3 for PFOA and PFOS imposed by the State of Michigan. The gas residence time of 4 seconds at a combustion temperature of 1150oC improved the total PFAS decomposition and lowered the air emission for PFOA and PFOS, compared to the 2 seconds GRT.

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

SpeakerOrr, Jon

Presentation time

9:00:00

9:30:00

Session time

8:30:00

11:45:00

SessionSession 10: PFAS Challenges and Treatment

Session number10

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicEmerging Issues (PFAS, Microplastics, Covid, etc.)