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Gomez‐Gonzalez MA, Rehkämper M, Han Z, Ryan MP, Laycock A, Porter AE. ZnO Nanomaterials and Ionic Zn Partition within Wastewater Sludge Investigated by Isotopic Labeling. Glob Chall 2022; 6:2100091. [PMID: 35284090 PMCID: PMC8902288 DOI: 10.1002/gch2.202100091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 12/08/2021] [Indexed: 06/14/2023]
Abstract
The increasing commercial use of engineered zinc oxide nanomaterials necessitates a thorough understanding of their behavior following their release into wastewater. Herein, the fates of zinc oxide nanoparticles (ZnO NPs) and ionic Zn in a real primary sludge collected from a municipal wastewater system are studied via stable isotope tracing at an environmentally relevant spiking concentration of 15.2 µg g-1. Due to rapid dissolution, nanoparticulate ZnO does not impart particle-specific effects, and the Zn ions from NP dissolution and ionic Zn display indistinguishable behavior as they partition equally between the solid, liquid, and ultrafiltrate phases of the sludge over a 4-h incubation period. This work provides important constraints on the behavior of engineered ZnO nanomaterials in primary sludge-the first barrier in a wastewater treatment plant-at low, realistic concentrations. As the calculated solid-liquid partition coefficients are significantly lower than those reported in prior studies that employ unreasonably high spiking concentrations, this work highlights the importance of using low, environmentally relevant doses of engineered nanomaterials in experiments to obtain accurate risk assessments.
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Affiliation(s)
- Miguel A. Gomez‐Gonzalez
- Department of Materials and London Centre for NanotechnologyImperial College LondonLondonSW7 2AZUK
| | - Mark Rehkämper
- Department of Earth Science & EngineeringImperial College LondonLondonSW7 2AZUK
| | - Zexiang Han
- Department of Materials and London Centre for NanotechnologyImperial College LondonLondonSW7 2AZUK
| | - Mary P. Ryan
- Department of Materials and London Centre for NanotechnologyImperial College LondonLondonSW7 2AZUK
| | - Adam Laycock
- UK Health Security AgencyCentre for RadiationChemical and Environmental HazardsHarwell Science and Innovation CampusDidcotOX11 0RQUK
| | - Alexandra E. Porter
- Department of Materials and London Centre for NanotechnologyImperial College LondonLondonSW7 2AZUK
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Zulli A, Pan A, Bart SM, Crawford FW, Kaplan EH, Cartter M, Ko AI, Sanchez M, Brown C, Cozens D, Brackney DE, Peccia J. Predicting daily COVID-19 case rates from SARS-CoV-2 RNA concentrations across a diversity of wastewater catchments. FEMS Microbes 2021; 2:xtab022. [PMID: 35128418 DOI: 10.1101/2021.04.27.21256140] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 01/06/2022] [Indexed: 05/20/2023] Open
Abstract
We assessed the relationship between municipality COVID-19 case rates and SARS-CoV-2 concentrations in the primary sludge of corresponding wastewater treatment facilities. Over 1700 daily primary sludge samples were collected from six wastewater treatment facilities with catchments serving 18 cities and towns in the State of Connecticut, USA. Samples were analyzed for SARS-CoV-2 RNA concentrations during a 10 month time period that overlapped with October 2020 and winter/spring 2021 COVID-19 outbreaks in each municipality. We fit lagged regression models to estimate reported case rates in the six municipalities from SARS-CoV-2 RNA concentrations collected daily from corresponding wastewater treatment facilities. Results demonstrate the ability of SARS-CoV-2 RNA concentrations in primary sludge to estimate COVID-19 reported case rates across treatment facilities and wastewater catchments, with coverage probabilities ranging from 0.94 to 0.96. Lags of 0 to 1 days resulted in the greatest predictive power for the model. Leave-one-out cross validation suggests that the model can be broadly applied to wastewater catchments that range in more than one order of magnitude in population served. The close relationship between case rates and SARS-CoV-2 concentrations demonstrates the utility of using primary sludge samples for monitoring COVID-19 outbreak dynamics. Estimating case rates from wastewater data can be useful in locations with limited testing availability, testing disparities, or delays in individual COVID-19 testing programs.
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Affiliation(s)
- Alessandro Zulli
- Department of Chemical and Environmental Engineering, School of Engineering and Applied Science, Yale University, 17 Hillhouse Ave, New Haven, CT, 06511, USA
| | - Annabelle Pan
- Department of Chemical and Environmental Engineering, School of Engineering and Applied Science, Yale University, 17 Hillhouse Ave, New Haven, CT, 06511, USA
| | - Stephen M Bart
- Epidemic Intelligence Service, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30329, USA
| | - Forrest W Crawford
- Department of Biostatistics, Yale School of Public Health, Yale University, 60 College Street, New Haven, CT, 06510, USA
| | - Edward H Kaplan
- Department of Chemical and Environmental Engineering, School of Engineering and Applied Science, Yale University, 17 Hillhouse Ave, New Haven, CT, 06511, USA
| | - Matthew Cartter
- Connecticut Department of Public Health, 410 Capitol Ave., Hartford, CT, 06134, USA
| | - Albert I Ko
- Department of Epidemiology of Microbial Disease, Yale School of Public Health, Yale University, 60 College Street, New Haven, CT, 06510, USA
| | - Marcela Sanchez
- Department of Chemical and Environmental Engineering, School of Engineering and Applied Science, Yale University, 17 Hillhouse Ave, New Haven, CT, 06511, USA
| | - Cade Brown
- Department of Chemical and Environmental Engineering, School of Engineering and Applied Science, Yale University, 17 Hillhouse Ave, New Haven, CT, 06511, USA
| | - Duncan Cozens
- Connecticut Agricultural Experimental Station, State of Connecticut, 123 Huntington St., New Haven, CT, 06511, USA
| | - Doug E Brackney
- Yale School of Public Health, Yale University, 60 College Street, New Haven, CT, 06510, USA
| | - Jordan Peccia
- Department of Chemical and Environmental Engineering, School of Engineering and Applied Science, Yale University, 17 Hillhouse Ave, New Haven, CT, 06511, USA
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Martin-Ryals AD, Schideman LC, Ong M. Utilizing bioaugmentation to improve performance of a two-phase AnMBR treating sewage sludge. Environ Technol 2020; 41:1322-1336. [PMID: 30301429 DOI: 10.1080/09593330.2018.1533041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 09/12/2018] [Indexed: 06/08/2023]
Abstract
Bioaugmentation in the acid-phase of a two-phase anaerobic membrane bioreactor (AnMBR) treating primary sludge was investigated as a means for targeting and improving hydrolysis and acetogenesis. Bioaugmentation was carried out using a proprietary bioculture blend containing a mixture of hydrolytic, acidogenic, and acetogenic microorganisms. This mixture was added on its own and in combination with recycled anaerobic sludge from the methane-phase of the AnMBR. Both bioaugmentation strategies had a positive effect on overall hydrolysis (25-38%), and acid-phase acetic acid generation (31-52%) compared to operation without bioaugmentation. This led to subsequent increases in average methane production (10-13%), and greater average solids reduction (25-55%). Microbial community analysis using 16S Illumina MiSeq generated sequences revealed increased relative abundance of Acetobacter and Syntrophomonas species in bioaugmented communities, suggesting these to be key players in improvements in process performance. However, in general the relative abundance of bioaugmented microorganisms within bioaugmented communities was relatively low, highlighting the need to optimize the bioculture composition and dosage. Overall, bioaugmentation was found to benefit the conversion of primary sludge to methane, when initial solubility was relatively low. Future work should optimize the bioculture composition and dosing strategy to improve its effectiveness and long-term stability, and minimize associated operating costs.
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Affiliation(s)
- Ana D Martin-Ryals
- Department of Agricultural and Biological Engineering, University of Illinois Urbana-Champaign, Urbana, IL, USA
| | - Lance C Schideman
- Department of Agricultural and Biological Engineering, University of Illinois Urbana-Champaign, Urbana, IL, USA
| | - Matthew Ong
- Department of Agricultural and Biological Engineering, University of Illinois Urbana-Champaign, Urbana, IL, USA
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Shewa WA, Dong T, Mu W, Murray K, Dagnew M. The impact of chemically enhanced primary treatment on the downstream liquid and solid train processes. Water Environ Res 2020; 92:359-368. [PMID: 31233649 DOI: 10.1002/wer.1170] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 06/12/2019] [Accepted: 06/18/2019] [Indexed: 06/09/2023]
Abstract
The use of chemical coagulants and flocculants to supplement chemically enhanced primary treatment (CEPT) processes is increasing in popularity as it has been demonstrated to improve carbon redirection and suspended solids and phosphorus removal. Dosing 15 mg ferric chloride/L of wastewater and poly aluminum chloride (PACl; 0.5 mg/L) to the influent of a primary clarifier successfully achieved improved carbon redirection and suspended solids removal at a full-scale WWTP. In this study, the impacts of PACl on the downstream liquid and solid train processes of the same WWTP were investigated. Compared to FeCl3 addition, a combined PACl and FeCl3 addition to the primary influent reduced the TSS and TP concentrations of the secondary clarifier effluent by 20% and 33%, respectively. Effluent BOD5 and ammonia-nitrogen concentrations of the downstream activated sludge process were not affected by the addition of a combined FeCl3 and PACl in the primary clarifier. PACl addition affects the bioavailability of carbon and hence reduced the methane production efficiency of the primary sludge by 20%-30%. However, the significant amount of carbon concentrated in the CEPT sludge would enhance the amount of energy recovered through incineration. PRACTITIONER POINTS: The chemically enhanced primary treatment process is an attractive method for carbon redirection and energy recovery. The combined FeCl3 and PACl addition in the primary clarifier improves the full scale activated sludge process effluent quality. PACl has a negative effect on methane production.
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Affiliation(s)
- Wudneh A Shewa
- Department of Civil and Environmental Engineering, Western University, London, ON, Canada
| | - Tianchen Dong
- Department of Civil and Environmental Engineering, Western University, London, ON, Canada
| | - Wenjuan Mu
- Department of Civil and Environmental Engineering, Western University, London, ON, Canada
| | | | - Martha Dagnew
- Department of Civil and Environmental Engineering, Western University, London, ON, Canada
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Solé-Bundó M, Salvadó H, Passos F, Garfí M, Ferrer I. Strategies to Optimize Microalgae Conversion to Biogas: Co-Digestion, Pretreatment and Hydraulic Retention Time. Molecules 2018; 23:E2096. [PMID: 30134563 PMCID: PMC6225242 DOI: 10.3390/molecules23092096] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 08/09/2018] [Accepted: 08/16/2018] [Indexed: 12/17/2022] Open
Abstract
This study aims at optimizing the anaerobic digestion (AD) of biomass in microalgal-based wastewater treatment systems. It comprises the co-digestion of microalgae with primary sludge, the thermal pretreatment (75 °C for 10 h) of microalgae and the role of the hydraulic retention time (HRT) in anaerobic digesters. Initially, a batch test comparing different microalgae (untreated and pretreated) and primary sludge proportions showed how the co-digestion improved the AD kinetics. The highest methane yield was observed by adding 75% of primary sludge to pretreated microalgae (339 mL CH₄/g VS). This condition was then investigated in mesophilic lab-scale reactors. The average methane yield was 0.46 L CH₄/g VS, which represented a 2.9-fold increase compared to pretreated microalgae mono-digestion. Conversely, microalgae showed a low methane yield despite the thermal pretreatment (0.16 L CH₄/g VS). Indeed, microscopic analysis confirmed the presence of microalgae species with resistant cell walls (i.e., Stigioclonium sp. and diatoms). In order to improve their anaerobic biodegradability, the HRT was increased from 20 to 30 days, which led to a 50% methane yield increase. Overall, microalgae AD was substantially improved by the co-digestion with primary sludge, even without pretreatment, and increasing the HRT enhanced the AD of microalgae with resistant cell walls.
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Affiliation(s)
- Maria Solé-Bundó
- GEMMA-Group of Environmental Engineering and Microbiology, Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya·BarcelonaTech, c/Jordi Girona 1-3, Building D1, E-08034 Barcelona, Spain.
| | - Humbert Salvadó
- Department of Evolutionary Biology, Ecology and Environmental Sciences, Faculty of Biology, Universitat de Barcelona, Av. Diagonal 643, 08007 Barcelona, Spain.
| | - Fabiana Passos
- Department of Sanitary and Environmental Engineering, Federal University of Minas Gerais, Antonio Carlos Avenue 6627, 31270-090 Belo Horizonte, Brazil.
| | - Marianna Garfí
- GEMMA-Group of Environmental Engineering and Microbiology, Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya·BarcelonaTech, c/Jordi Girona 1-3, Building D1, E-08034 Barcelona, Spain.
| | - Ivet Ferrer
- GEMMA-Group of Environmental Engineering and Microbiology, Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya·BarcelonaTech, c/Jordi Girona 1-3, Building D1, E-08034 Barcelona, Spain.
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Pittmann T, Steinmetz H. Polyhydroxyalkanoate Production on Waste Water Treatment Plants: Process Scheme, Operating Conditions and Potential Analysis for German and European Municipal Waste Water Treatment Plants. Bioengineering (Basel) 2017; 4:E54. [PMID: 28952533 DOI: 10.3390/bioengineering4020054] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 06/02/2017] [Accepted: 06/03/2017] [Indexed: 12/04/2022] Open
Abstract
This work describes the production of polyhydroxyalkanoates (PHA) as a side stream process on a municipal waste water treatment plant (WWTP) and a subsequent analysis of the production potential in Germany and the European Union (EU). Therefore, tests with different types of sludge from a WWTP were investigated regarding their volatile fatty acids (VFA) production-potential. Afterwards, primary sludge was used as substrate to test a series of operating conditions (temperature, pH, retention time (RT) and withdrawal (WD)) in order to find suitable settings for a high and stable VFA production. In a second step, various tests regarding a high PHA production and stable PHA composition to determine the influence of substrate concentration, temperature, pH and cycle time of an installed feast/famine-regime were conducted. Experiments with a semi-continuous reactor operation showed that a short RT of 4 days and a small WD of 25% at pH = 6 and around 30 °C is preferable for a high VFA production rate (PR) of 1913 mgVFA/(L×d) and a stable VFA composition. A high PHA production up to 28.4% of cell dry weight (CDW) was reached at lower substrate concentration, 20 °C, neutral pH-value and a 24 h cycle time. A final step a potential analysis, based on the results and detailed data from German waste water treatment plants, showed that the theoretically possible production of biopolymers in Germany amounts to more than 19% of the 2016 worldwide biopolymer production. In addition, a profound estimation regarding the EU showed that in theory about 120% of the worldwide biopolymer production (in 2016) could be produced on European waste water treatment plants.
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Mendes CVT, Rocha JMDS, de Menezes FF, Carvalho MDGVS. Batch and fed-batch simultaneous saccharification and fermentation of primary sludge from pulp and paper mills. Environ Technol 2017; 38:1498-1506. [PMID: 27611735 DOI: 10.1080/09593330.2016.1235230] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 09/05/2016] [Indexed: 06/06/2023]
Abstract
Primary sludge from a Portuguese pulp and paper mill, containing 60% of carbohydrates, and unbleached pulp (as reference material), with 93% of carbohydrates, were used to produce ethanol by simultaneous saccharification and fermentation (SSF). SSF was performed in batch or fed-batch conditions without the need of a pretreatment. Cellic® CTec2 was the cellulolytic enzymatic complex used and Saccharomyces cerevisiae (baker's yeast or ATCC 26602 strain) or the thermotolerant yeast Kluyveromyces marxianus NCYC 1426 were employed. Primary sludge was successfully converted to ethanol and the best results in SSF efficiency were obtained with S. cerevisiae. An ethanol concentration of 22.7 g L-1 was produced using a content of 50 g L-1 of carbohydrates from primary sludge, in batch conditions, with a global conversion yield of 81% and a production rate of 0.94 g L-1 h-1. Fed-batch operation enabled higher solids content (total carbohydrate concentration of 200 g L-1, equivalent to a consistency of 33%) and a reduction of three-quarters of cellulolytic enzyme load, leading to an ethanol concentration of 40.7 g L-1, although with lower yield and productivity. Xylitol with a concentration up to 7 g L-1 was also identified as by-product in the primary sludge bioconversion process.
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Affiliation(s)
- Cátia Vanessa Teixeira Mendes
- a CIEPQPF, Department of Chemical Engineering, Faculty of Sciences and Technology , University of Coimbra , Coimbra , Portugal
| | - Jorge Manuel Dos Santos Rocha
- a CIEPQPF, Department of Chemical Engineering, Faculty of Sciences and Technology , University of Coimbra , Coimbra , Portugal
| | - Fabrícia Farias de Menezes
- a CIEPQPF, Department of Chemical Engineering, Faculty of Sciences and Technology , University of Coimbra , Coimbra , Portugal
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Obulisamy PK, Chakraborty D, Selvam A, Wong JWC. Anaerobic co-digestion of food waste and chemically enhanced primary-treated sludge under mesophilic and thermophilic conditions. Environ Technol 2016; 37:3200-3207. [PMID: 27315419 DOI: 10.1080/09593330.2016.1181112] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Anaerobic co-digestion of food waste with primary sewage sludge is beneficial for urban centers, while the optimized conditions reported in the literature are not locally suitable for Hong Kong. Therefore, the present study was aimed to develop an optimized mixing ratio of food waste to chemically enhanced primary-treated sewer sludge (CEPT) for co-digestion using batch tests under mesophilic (37°C) and thermophilic (55°C) conditions. The mixing ratios of 1:1, 1:2, 1:3, 2:1 and 3:1 (v v(-1)) of food waste to CEPT sludge was tested under the following conditions: temperature - 35°C and 55°C; pH - not regulated; agitation - 150 rpm and time - 20 days. The thermophilic incubations led a good hydrolysis rate and 2-12-fold higher enzyme activities than in mesophilic incubations for different mixing ratios. While the acidogenesis were found retarded that leading to 'sour and stuck' digestion for all mixing ratio of food waste to CEPT sludge from thermophilic incubations. The measured zeta potential was most favourable (-5 to -16.8 mV) for methane production under thermophilic incubations; however the CH4 recovery was less than that in mesophilic incubations. The results suggested that the quick hydrolysis and subsequent acid accumulation under thermophilic incubation lead to inhibited methanogenesis at the early stage than in mesophilic systems. It is concluded that buffer addition is therefore required for any mixing ratio of food waste to CEPT sludge for improved CH4 recovery for both mesophilic and thermophilic operations.
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Affiliation(s)
- Parthiba Karthikeyan Obulisamy
- a Sino-Forest Applied Research Centre for Pearl River Delta Environment , Hong Kong Baptist University , Kowloon Tong , Hong Kong SAR, People's Republic of China
- b Department of Biology , Hong Kong Baptist University , Kowloon Tong , Hong Kong SAR, People's Republic of China
| | - Debkumar Chakraborty
- a Sino-Forest Applied Research Centre for Pearl River Delta Environment , Hong Kong Baptist University , Kowloon Tong , Hong Kong SAR, People's Republic of China
- b Department of Biology , Hong Kong Baptist University , Kowloon Tong , Hong Kong SAR, People's Republic of China
| | - Ammaiyappan Selvam
- a Sino-Forest Applied Research Centre for Pearl River Delta Environment , Hong Kong Baptist University , Kowloon Tong , Hong Kong SAR, People's Republic of China
- b Department of Biology , Hong Kong Baptist University , Kowloon Tong , Hong Kong SAR, People's Republic of China
| | - Jonathan W C Wong
- a Sino-Forest Applied Research Centre for Pearl River Delta Environment , Hong Kong Baptist University , Kowloon Tong , Hong Kong SAR, People's Republic of China
- b Department of Biology , Hong Kong Baptist University , Kowloon Tong , Hong Kong SAR, People's Republic of China
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Hamid H, Eskicioglu C. Effect of microwave hydrolysis on transformation of steroidal hormones during anaerobic digestion of municipal sludge cake. Water Res 2013; 47:4966-4977. [PMID: 23866136 DOI: 10.1016/j.watres.2013.05.042] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 05/20/2013] [Accepted: 05/21/2013] [Indexed: 06/02/2023]
Abstract
Fate and removal of 16 steroidal (estrogenic, androgenic and progestogenic) hormones were studied during advanced anaerobic digestion of sludge cake using microwave (MW) pretreatment. Effect of pretreatment temperature (80, 120, 160 °C), operating temperature (mesophilic at 35 ± 2 °C, thermophilic at 55 ± 2 °C) and sludge retention time (SRT: 20, 10, 5 days) were studied employing eight lab-scale semi-continuously fed digesters. To determine the potential effect of MW hydrolysis, hormones were quantified in total (sorbed + soluble) and supernatant (soluble) phases of the digester influent and effluent streams. Seven of 16 hormones were above the method reporting limit (RL) in one or more of the samples. Hormone concentrations in total phase of un-pretreated (control) and pretreated digester feeds ranged in <157-2491 ng/L and <157-749 ng/L, respectively. The three studied factors were found to be statistically significant (95% confidence level) in removal of one or more hormones from soluble and/or total phase. MW hydrolysis of the influent resulted in both release (from sludge matrix) and attenuation of hormones in the soluble phase. Accumulation of estrone (E1) as well as progesterone (Pr) and androstenedione (Ad) in most of the digesters indicated possible microbial transformations among the hormones. Compared to controls, all pretreated digesters had lower total hormone concentrations in their influent streams. At 20 days SRT, highest total removal (E1+E2+Ad +Pr) was observed for the thermophilic control digester (56%), followed by pretreated mesophilic digesters at 120 °C and 160 °C with around 48% efficiency. In terms of conventional performance parameters, relative (to control) improvements of MW pretreated digesters at a 5-d SRT ranged in 98-163% and 57-121%, for volatile solids removal and methane production, respectively.
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Affiliation(s)
- Hanna Hamid
- School of Engineering, University of British Columbia, Okanagan Campus, 1137 Alumni Ave., Kelowna, BC V1V 1V7, Canada
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