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Start-up and operation of an Upflow Anaerobic Sludge Blanket (UASB) reactor fed with an industrial effluent from a polymer synthesis plant containing 6 mg styrenel–1 was unstable. In batch assays with 200 mg styrenel–1, 74% of styrene was degraded at a rate of 7ml methaneg–1 volatile suspended solids.day, without a lag phase. The toxicity limit (IC...
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... accumulation of toxic compounds in the envi- ronment has increased with industrial production of pesticides, pigments, derivates of the paper, plastics and polymers. Styrene has greatly increased its par- ticipation in the market of synthetic products. As an example, its estimated United States production in 1999 was 5.5 × 10 9 tons (Chemical Market Associates Inc. 1999). Styrene is mainly used as synthetic monomer for plastics production of electronic and do- mestic hardware and in the manufacture of reinforced plastics. Its structure is presented in Figure 1. Short-term exposure to styrene leads to mucous membrane and eye irritations, whereas long-term exposure affects the central nervous system, increasing the risk of leukemia and lymphoma. It is pointed out as a possible human carcinogen compound (Environmental Protection Agency 2000). Due to its high volatility, styrene emissions to the atmosphere have steadily increased during the last years, leading to the development of gas treatment processes (Pol et al. 1998). However, in spite of its high volatility, a frac- tion of styrene remains in the liquid phase of industrial effluents, being potentially toxic to the biomass used in biological treatment processes. Effluents from chemical industry present, in general, unfavorable environmental characteristics for the growth of microorganisms such as extreme pH, high temperatures and presence of toxic compounds. It is the case, for example, of effluents from plastic and pharmaceutical industry. Aerobic treatment systems have been traditionally used for this kind of effluent, being the anaerobic technology not so widely applied due to the lack of knowledge regarding the effects of some toxics on the anaerobic consortia. There are only a few publications reporting the use of anaerobic treatment with effluents of this type of industry (Araya et al. 1999, Henry et al . 1996). Araya et al. (1999) reported that an effluent from a polymer synthesis plant was efficiently treated in a Upflow Anaerobic Sludge Blanket (UASB) reactor after a gradual acclimatization to the effluent. In the present work, the influence of a start-up period without acclimatization was eval- uated for the same type of effluent in a UASB reactor. As styrene was the main aromatic compound present in the effluent, the anaerobic biodegradability and toxicity of this compound was studied in batch assays, evaluating its effect on some key bacterial groups of the anaerobic consortium, such as acetoclastic and syntrophic ...
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... Consequently, we researched inhibition data for components from these main groups. Inhibition data were scarce for these types of components and were only found for acetoclastic methanogens [30][31][32][33]. Four components were selected, that are at the same time found in high amounts in syngas and have available inhibitory data in the literature: benzene, toluene, styrene and phenol. ...
In a circular economy approach, syngas biomethanation is a promising technology for waste to energy conversion. However, syngas can contain impurities, notably tar, that can limit the processes upgrading syngas downstream gasification. The effect of tar on syngas biomethanation is unknown. Therefore, for the first time, common tar components were tested on a consortium adapted for syngas biomethanation to assess the resistance of the microorganisms. Four light tar components (benzene, toluene, styrene and phenol) commonly found in syngas were selected and tested at different concentrations in batch tests. Adding pollutant up to inhibitory concentrations affected both the lag phase of microbial growth and the rates of the bioreactions. Hydrogenotrophic methanogens were found to be more sensitive than carboxydotrophs. Amongst the four tested pollutants, phenol appears to be the most problematic, due not only to its high inhibitory effect but also to its high solubility, allowing phenol in the syngas to reach high inhibitory concentrations. This study paves the way for further research on the resistance of syngas biomethanation to impurities contained in the syngas.
Graphical Abstract
... The anaerobic systems not only reduce the energy consumption in comparison with aerobic systems because of aeration removal but also have the potential to produce energy and to prevent the volatile compounds from stripping. Although there are limited studies about the anaerobic biodegradation of styrene, the results have shown that styrene can be successfully biodegraded anaerobically [12,13]. Styrene was used for the production of biogas by anaerobic degradation; for example, Araya et al. studied styrene biodegradation in a upflow anaerobic sludge blanket (UASB) reactor. ...
... According to their results, 74% of styrene was degraded. However, the methane production rate was only 7 mL CCH 4(STP) gVSS − 1 d − 1 ADDINCITAVI.PLACEHOLDER [13]. So, the biogas production from styrene degradation was low. ...
... To the best of our knowledge, there are limited studies [12][13][14] focused on anaerobic biological treatment of wastewater containing styrene and almost no research on the application of MFC for degradation of styrene or production of power using it. This study aims to investigate styrene degradation at high concentrations and power generation in an MFC by using activated sludge as inoculum. ...
Industrial wastewaters containing styrene produced from industrial units have posed significant environmental and health issues. Microbial Fuel Cell (MFC) could be used as a biotechnological system in volatile organic compound (VOC) degradation, including styrene bioremediation, especially in anaerobic conditions to prevent it from being stripped into the gaseous phase. In the present study, the biodegradation of styrene in the concentration range of 27–105.7 mg L-1 using adapted and unadapted activated sludge as inoculum was investigated in MFCs with respect to degradation rate, degradation efficiency, and power production. Results indicated that the two inoculums tested could lead to efficient degradation of styrene, but the degradation rate and power production of the adapted activated sludge is higher than the unadapted ones. The best performing inoculum, the adapted activated sludge, gave styrene an initial degradation rate of 15.6 mgL-1h-1, the maximum power density of 13.6 mWm-2,and styrene removal of 100%. The Gas Chromatography/Mass Spectrometry (GC/MS) test shows that the phenyl acetate route can be proposed as the dominant mechanism. Methylene blue, methyl orange, and methyl red were used as electron acceptors, and their influence on MFC performance was investigated. The addition of methylene blue achieved a 1.22-fold increase in steady state voltage from 233 mV in the absence of any added mediator to 285 mV in the presence of methylene blue. The present study highlights the possibility of using MFC to achieve efficient treatment of styrene-contaminated wastewater by using activated sludge as an inoculum with concomitant bioelectricity production and showing the influence of the microorganism adaptation to the styrene on power generation.
... In one of these studies, Grbić-Galić et al. (1990) investigated the transformation of styrene (0.1-10 mmol/L) by anaerobic sewage sludge enriched by methanogenic microorganisms. Araya et al. (2000) and Dangcong et al. (1994) assessed the effect of seed sludge morphology on the performance of an up-flow anaerobic sludge blanket (UASB) reactor in treating toxic wastewater containing styrene. However, to the authors' knowledge, there has been no comprehensive investigation on the effect of digestion temperature and styrene concentration in the wastewater on the anaerobic biodegradation/volatilization of styrene and biogas production. ...
... They have stated that the high toxicity of styrene or some of its degradation products such as phenol or 2ethylphenol could prevent methane from being produced. On the other hand,Araya et al. (2000) have reported that during anaerobic digestion of synthetic wastewater containing 200 ppm styrene as the only carbon source, methane was produced at a rate of 7 ml CH4.g -1 MLVSS.day -1 .Consistent with the Buswell formula (Equation 2), which represents a balanced reaction for the production of methane under the assumption that organic matter (e.g., CnHaOb) is wholly degraded to methane, the theoretical amount of methane from styrene and ethanol can be determined ...
In the current study, styrene was removed anaerobically from wastewaters at temperatures of 35 ℃, 25 ℃, and 15 ℃ and concentration range of 20-150 ppm in the presence of ethanol as a co-substrate and co-solvent. Maximum styrene removal of 93% was achieved at 35 ℃. The volatilization of styrene was negligible at about 2% at all experimented temperatures. The average special methane yield (SMY) at 35 ℃ was 4.14- and 225-times higher than that of at T = 25 ℃ and T = 15 ℃, respectively, but no methane was produced in the absence of ethanol. The proteins content of the soluble microbial product (SMP) and extracellular polymeric substance (EPS) was much higher than the carbohydrate content. At styrene concentration > 80 ppm, SMY, SMP, and EPS dropped sharply. The results confirmed the well performance of anaerobic microorganisms in removing styrene from wastewater and biogas production at mesophilic condition.
... Increased COD loading from 5 to 20 gCOD/L reduced methane production substantially, from approximately 216 to 50 mL CH 4 / gCOD. In another study, batch anaerobic experiments Blum and Speece (1991) b Araya et al. (2000) were performed at 0.75 gCOD/L using HTL-AP derived from dewatered sewage sludge processed under a range of temperatures and residence times of 140-320°C and 0.5-6 h, respectively (Chen et al. 2019). Increased temperature and residence time led to decreased methane production from 286 to 136 mL CH 4 /g COD with HTL-AP at 170 and 320°C, respectively, and from 242 to 161 mL CH 4 /g COD when residence time increased from 0.5 to 6 h (using 200°C HTL-AP) (Chen et al. 2019). ...
Pyrolysis and hydrothermal liquefaction (HTL) are potential technologies for renewable energy production and waste valorization using municipal wastewater sewage sludge and other lignocellulosic biomass. However, the organic-rich aqueous pyrolysis liquid (APL) and HTL aqueous phase (HTL-AP) produced currently have no apparent use and are challenging to manage. Furthermore, the toxic organic compounds in them can be harmful to the environment. Anaerobic digestion (AD) may be a viable method to manage the liquids and recover energy in APL and HTL-AP in form of methane-rich biogas. Integrating thermochemical processes with AD could promote a circular economy by recovering resources and reducing environmental pollution. The challenge, however, is the presence of toxic compounds recalcitrant to anaerobic biodegradation such as phenols and nitrogen-containing organics that can inhibit methane-producing microbes. This review presents information on APL and HTL-AP characterization and biodegradability. Feedstock composition and process operational parameters are major factors affecting APL and HTL-AP composition, subsequent toxicity, and degradability. Feedstocks with high nitrogen content as well as increased thermochemical processing temperature and retention time result in a more toxic aqueous liquid and lower methane yield. Dilution and low AD organic loading are required to produce methane. More comprehensive APL and HTL-AP chemical characterization is needed to adopt suitable treatment strategies. Pretreatments such as overliming, air stripping, partial chemical oxidation, adsorption, and solvent extraction of toxic constituents as well as co-digestion and microbial acclimatization successfully reduce toxicity and increase methane yield.
Graphic abstract
... Denitrification in anoxic zones of the filling bed might deplete nitrogen as a source for biomass production and release molecular nitrogen via the exhaust air. Single isolates as well as mixed cultures have been reported to be able to consume styrene under anoxic conditions, although not much is known about the degradation pathways [69,70]. Six of the initial 17 styrene degrading strains used as inocula for the pilot-scale plant were found to be able to grow anaerobically on styrene. ...
A combined system of a biotrickling filter and a non-thermal plasma (NTP) in a downstream airflow was operated for 1220 days for treatment of emissions of styrene and secondary emissions of germs formed in the biological process. The biotrickling filter was operated at variable inlet concentrations, empty bed residence times (EBRT), type and dosage of fertilizers, irrigation densities, and starvation periods, while dielectric barrier discharge and corona discharge were operated at different specific input energy levels to achieve optimal conditions. Under these conditions, efficiencies in the removal of volatile organic compounds (VOCs), germs and styrene of 96–98%, 1–4 log units and 24.7–50.1 g C m−3 h−1 were achieved, respectively. Fluid simulations of the NTP and a germ emission-based clocking of the discharge reveal further energy saving potentials of more than 90%. The aim of an energy-efficient elimination of VOCs through a biotrickling filter and of secondary germ emissions by a NTP stage in a downstream airflow for potential re-use of purified waste gas as process gas for industrial application was successfully accomplished.
... This could be attributed to the potential interaction between the styrene monomers and microorganisms. Styrene monomers have proven to be toxic to microbes in anaerobic treatment systems [46], and could potentially act as a negative chemical cue for the settlement of microorganisms. ...
Trillions of plastic debris fragments are floating at sea, presenting a substantial surface area for microbial colonization. Numerous cultivation-independent surveys have characterized plastic-associated microbial biofilms, however, quantitative studies addressing microbial carbon biomass are lacking. Our confocal laser scanning microscopy data show that early biofilm development on polyethylene, polypropylene, polystyrene, and glass substrates displayed variable cell size, abundance, and carbon biomass, whereas these parameters stabilized in mature biofilms. Unexpectedly, plastic substrates presented lower volume proportions of photosynthetic cells after 8 weeks, compared to glass. Early biofilms displayed the highest proportions of diatoms, which could influence the vertical transport of plastic debris. In total, conservative estimates suggest 2.1 × 1021 to 3.4 × 1021 cells, corresponding to about 1% of the microbial cells in the ocean surface microlayer (1.5 × 103 to 1.1 × 104 tons of carbon biomass), inhabit plastic debris globally. As an unnatural addition to sea surface waters, the large quantity of cells and biomass carried by plastic debris has the potential to impact biodiversity, autochthonous ecological functions, and biogeochemical cycles within the ocean.
... In one of these studies, Grbić-Galić et al. (1990) investigated the transformation of styrene (0.1-10 mmol/L) by anaerobic sewage sludge enriched by methanogenic microorganisms. Araya et al. (2000) and Dangcong et al. (1994) assessed the effect of seed sludge morphology on the performance of an up-flow anaerobic sludge blanket (UASB) reactor in treating toxic wastewater containing styrene. However, to the authors' knowledge, there has been no comprehensive investigation on the effect of digestion temperature and styrene concentration in the wastewater on the anaerobic biodegradation/volatilization of styrene and biogas production. ...
... They have stated that the high toxicity of styrene or some of its degradation products such as phenol or 2-ethylphenol could prevent methane from being produced. On the other hand, Araya et al. (2000) have reported that during anaerobic digestion of synthetic wastewater containing 200 ppm styrene as the only carbon source, methane was produced at a rate of 7 mL CH 4 .g − 1 MLVSS.day ...
Optimal production of lignocellulosic bioethanol is hindered due to commonly faced issues with the presence of inhibitory compounds and sequentially consumed sugars in the lignocellulosic hydrolysate. Therefore, in order to find a robust fermentation approach, this study aimed at enhancing simultaneous co-assimilation of sugars, and inhibitor tolerance and detoxification. Therefore, fermentation of toxic wheat straw hydrolysate containing up to 20 g/l furfural, using the concentration-driven diffusion-based technique of reverse membrane bioreactor (rMBR) was studied. The rMBR fermentation of the hydrolysate led to complete furfural detoxification and the conversion of 87 % of sugars into ethanol at a yield of 0.48 g/g. Moreover, when the toxicity level of the hydrolysate was increased to 9 g/l of initial furfural, the system responded exceptionally by reducing 89 % of the inhibitor while only experiencing about 25 % drop in the ethanol yield. In addition, using this diffusion-based set-up in extremely inhibitory conditions (16 g/l furfural), cells could detoxify 40 % of the furfural at a high initial furfural to cell ratio of 9.5:1. The rMBR set-up applied proved that by properly synchronizing the medium condition, membrane area, and inhibitor to cell ratio, some of the shortcomings with conventional lignocellulosic fermentation can be tackled, guaranteeing a robust fermentation.
... Clearly, the cellular toxicity of styrene as well as the necessity of its removal greatly limit in vivo biosynthesis titers and the feasibility of commercial styrene https://doi.org/10.1016/j.ymben.2020.05.009 Received 21 February 2020; Received in revised form 13 May 2020; Accepted 25 May 2020 biosynthesis (Araya et al., 2000). Circumventing cellular toxicity could prove useful for the biochemical production of styrene. ...
Styrene is an important petroleum-derived molecule that is polymerized to make versatile plastics, including disposable silverware and foamed packaging materials. Finding more sustainable methods, such as biosynthesis, for producing styrene is essential due to the increasing severity of climate change as well as the limited supply of fossil fuels. Recent metabolic engineering efforts have enabled the biological production of styrene in Escherichia coli , but styrene toxicity and volatility limit biosynthesis in cells. To address these limitations, we have developed a cell-free styrene biosynthesis platform. The cell-free system provides an open reaction environment without cell viability constraints, which allows exquisite control over reaction conditions and greater carbon flux toward product formation rather than cell growth. The two biosynthetic enzymes required for styrene production were generated via cell-free protein synthesis and mixed in defined ratios with supplemented L-phenylalanine and buffer. By altering the time, temperature, pH, and enzyme concentrations in the reaction, this approach increased the cell-free titer of styrene from 5.36 ± 0.63 mM to 40.33 ± 1.03 mM, an order of magnitude greater than cellular synthesis methods. Cell-free systems offer a complimentary approach to cellular synthesis of small molecules, which can provide particular benefits for producing toxic molecules.
Highlights
A cell-free system for styrene biosynthesis was established. This in vitro system achieved styrene titers an order of magnitude greater than the highest reported concentration in vivo.
... Therefore, air stripping of catalyzed APL removed the volatile organic chemicals, ethylbenzene, and styrene. The IC 50 values of ethylbenzene and styrene to unacclimated methanogenic biomass are each approximately 150 mg/L (Blum and Speece, 1991;Araya et al., 2000). Removing these potentially inhibitory chemicals from APL in addition to NH 3 -N by air stripping may have resulted in reduced APL toxicity. ...
Aqueous pyrolysis liquid (APL) is a high-COD byproduct of wastewater biosolids pyrolysis that is comprised of numerous complex organic compounds and ammonia nitrogen (NH3-N). One potential beneficial use of APL is as a co-digestate to produce more biogas in anaerobic digesters. However, some APL organics and NH3-N are known to inhibit methane-producing microbes. Autocatalytic pyrolysis which uses previously-produced biochar as a catalyst during biosolids pyrolysis, increases energy-rich py-gas while eliminating bio-oil production and reducing COD concentration in the APL (catalyzed APL). However, the catalyzed APL still has a high organic strength and no suitable treatment strategies have yet been identified. In this study, the methane production yields and methanogenic toxicity of non-catalyzed and catalyzed APLs were investigated. Both non-catalyzed and catalyzed APLs were produced at 800°C from a mix of digested primary and raw waste activated sludge from a municipal water resource reclamation facility. Using the anaerobic toxicity assay, APL digester loading rates higher than 0.5 gCOD/L for non-catalyzed and 0.10 gCOD/L for catalyzed APL were not sustainable due to toxicity. The IC50 values (APL concentration that inhibited methane production rate by 50%) for non-catalyzed and catalyzed APLs were 2.3 and 0.3 gCOD/L, respectively. Despite having significantly fewer identified organic compounds catalytic APL resulted in higher methanogenic toxicity than non-catalytic APL. NH3-N was not the main inhibitory constituent and other organics in APL, including 3,5-dimethoxy-4-hydroxybenzaldehyde, 2,5-dimethoxybenzyl alcohol, benzene, cresol, ethylbenzene, phenols, styrene, and xylenes as well as nitrogenated organics (e.g., benzonitrile, pyridine) ostensibly caused considerable methane production inhibition. Future research focused on pretreatment methods to overcome APL toxicity and the use of acclimated biomass to increase methane production rates during APL anaerobic digestion or co-digestion is warranted.
... values of ethylbenzene and styrene to unacclimated methanogenic biomass are approximately 160 mg/L (Blum & Speece, 1991) and 150 mg/L (Araya et al., 2000), respectively. Removing these potentially inhibitory chemicals from APL by aeration may result in reduced inhibition when anaerobically digesting the APL. ...
ANAEROBIC CO-DIGESTION OF AQUEOUS LIQUID FROM BIOSOLIDS PYROLYSIS Seyedehfatemeh Seyedi Marquette University, 2018 Pyrolysis is a process to treat biosolids and recover energy. During pyrolysis, conversion of organic matter to energy-rich products yields biochar, py-gas, and pyrolysis liquids (aqueous phase and non-aqueous bio-oil). The aqueous pyrolysis liquid (APL), is a high-COD liquid with no apparent use that contains polycyclic aromatic hydrocarbons and nitrogen-containing compounds. One potential beneficial use of APL is as a co-digestate to produce more biogas for renewable energy from anaerobic digesters at municipal water resource recovery facilities. Some of the organics in APL may be converted to biomethane via anaerobic digestion under proper conditions. However, some APL organics are known to inhibit methane-producing microbes. Biosolids APL can also contain high concentrations of NH3-N that inhibit methane production. In this study, sustainable, unacclimated anaerobic digester organic loading rates for APL from biosolids pyrolysis were determined using anaerobic toxicity assays (ATA). APL loading rates higher than 0.5 gCOD/L for non-catalyzed APL and 0.10 g COD/L for catalyzed APL were not sustainable due to toxicity. By means of pretreatment by NH3-N air stripping, the potential toxicity exerted from NH3-N was decreased considerably (>80%). NH3-N was not the main inhibitory constituent and other organic constituents in APL caused considerable inhibition of methane production. In subsequent testing, continuous co-digestion of APL and synthetic wastewater primary sludge was performed while digester function and microbial community composition changes were evaluated. During quasi steady state operation, digesters that received catalyzed APL exhibited greater inhibition of methane production than digesters fed non-catalyzed APL. However, NH3-N stripping in non-catalyzed APL increased methane production rate; additional methane production was observed when non-catalyzed aerated APL was co-digested (1.5 ± 1.7 mL/day extra methane). Shifts in the Archaeal community composition in inhibited digesters (received catalyzed APL) versus uninhibited digesters (control digesters and digesters received non-catalyzed APL) was observed. The archaeal genus Methanosaeta dominated in uninhibited digesters, whereas in inhibited digesters hydrogenotrophic Methanobrevibacter was dominant and growth of acetate-consuming Archaea (i.e., Methanosaeta) was inhibited. Inhibited digesters had distinctly different Bacterial community composition from those in uninhibited digesters and Clostridium was the dominant Bacterial genus in all digesters. Results suggested that the microbes started to acclimate to the catalyzed APL; however, using an already acclimated biomass may be more efficient. A future study using acclimated biomass by bioaugmentation could be used to prove this hypothesis. i ACKNOWLEDGMENT Seyedehfatemeh Seyedi I would like to express my sincere gratitude to my thesis advisor Dr. Daniel H. Zitomer for giving me the opportunity to study for my graduate degree at Marquette University. I am deeply thankful for his patience, and encouragement throughout my studies. He has taught me the methodology to carry out the research and to present the research works as clearly as possible and it was a great honor to work under his supervision. I appreciate all his contributions of time, ideas, and funding to make my master's degree experience productive.
