The aim of this study was to assess the feasibility of co-digesting lipids originated from domest... more The aim of this study was to assess the feasibility of co-digesting lipids originated from domestic wastewater along with sewage sludge. Three lab-scale single stage mesophilic anaerobic digesters were operated under a constant hydraulic retention time (15 days). One system (C) was fed on a daily basis with sewage sludge and served as the control system and its operation was compared with two experimental systems (E1 and E2). Both experimental systems received mixtures of sludge and lipids with different lipids content (20 % for system E1 and 60 % for system E2 on a VS basis), whereas organic loadings were 2 KgVS m-3 d-1 and 3,5 KgVS m-3 d-1 for systems E1 and E2, respectively. According to the results it can be stated that the addition of lipids to sewage sludge up to 60 % on a VS basis resulted in a significant increase of biogas production without producing any severe effects on the properties of the digested sludge. More specifically biogas production of reactor E1 was 18 % grea...
Endocrine disrupting chemicals and non-steroidal anti-inflammatory drugs are two important groups... more Endocrine disrupting chemicals and non-steroidal anti-inflammatory drugs are two important groups of emerging pollutants due to their toxicological and chemical characteristics and their persistent detection in the aquatic environment. Wastewater treatment plants are a significant pathway for their transfer to the water courses. It is well evidenced that these chemicals are only partially removed through biological treatment of wastewater and therefore being detected in secondary effluents. This work focuses on the evaluation of the efficiency of two well-established disinfection technologies (chlorination and UV irradiation) along with UV/H2O2 and powdered activated carbon (PAC) to remove these chemicals from biologically treated wastewater. Based on the results it is shown that appreciable removal efficiencies due to chlorination should be expected for most of the target compounds, whereas this was not the case for ibuprofen and ketoprofen. With the exemption of diclofenac and ketoprofen direct UV irradiation did not efficiently removed target compounds for UV doses usually applied for disinfection purposes. The application of advanced UV treatment through the addition of H2O2 although resulted in increased removal of the target compounds is not sufficient at moderate UV and H2O2 doses to achieve satisfactory removal efficiencies. PAC use resulted in sufficient removal of target compounds although high PAC doses were required for some chemicals. Comparison of Freundlich isotherms of this study with those of other studies, derived employing water samples, suggested that the water matrix along with the target compounds concentration range can significantly affect the outcome of the experiments.
Trichloroethylene (TCE), a compound classified as carcinogenic substance, is widely used in indus... more Trichloroethylene (TCE), a compound classified as carcinogenic substance, is widely used in industrial and commercial sectors. Its improper storage and/or neglectful disposal have resulted in groundwater contamination in industrialized sites all over the world. Microbial anaerobic reductive dechlorination is an important mechanism of in situ remediation of groundwater contaminated with chlorinated ethenes, since it can transform TCE to ethene by gradually disengaging three chlorine atoms. However, incomplete TCE reduction is a problem due to the accumulation of the toxic intermediates of cis-dichloroethylene (cDCE) and vinyl chloride (VC). This accumulation may be caused by interdependent factors, such as the suitability and the quantity of electron donor and the composition of the microbial community. The addition of electron donors to the subsurface (biostimulation) can significantly enhance reductive dechlorination efficiency, by stimulating the native dechlorinating population. ...
The collective literature on dechlorination performance in the presence of sulfate can be interpr... more The collective literature on dechlorination performance in the presence of sulfate can be interpreted to suggest that dechlorination at sites with elevated sulfate concentrations may be incomplete. Previous work comparing laboratory and field data concluded that the presence of sulfate in sites contaminated with trichloroethylene (TCE) might delay dechlorination but not preclude its completion. To further reconcile these conflicting reports, this work studied quantitatively the effect of sulfate on TCE biotransformation with the aid of a series of laboratory batch experiments, some up to one year-long. Specifically, the aim of the study was three-fold: to confirm whether indeed complete dechlorination is possible under sulfate-reducing conditions, to quantify the delay of dechlorination with suitable metrics, and to investigate whether this delay can be reduced by increasing the quantity of the supplied electron donor. In experiments with initial sulfate concentrations of 1.56 mM (1...
The collective literature suggests that cheese whey powder is a low cost material and an efficien... more The collective literature suggests that cheese whey powder is a low cost material and an efficient substrate to support microbial inorganic or organic pollutants removal. This study investigates the effectiveness of liquid cheese whey as an electron donor on reductive dechlorination of TCE for the replacement of butyrate, an industrial-grade chemical. Results show that liquid cheese whey can be used as an electron donor, since complete transformation of TCE to ethene was achieved with two high and low carbon-content grades. Although dechlorination rate was slower compared with a butyrate-fed experiment, cost savings may outweigh possible delays in dechlorination progress. Moreover, high donor concentrations slightly decrease the rate of reductive dechlorination. The above findings lead to the conclusion that the use of liquid whey or a combined usage of liquid/powder whey may be a viable and cost effective strategy to achieve dechlorination in the field.
Bulletin of environmental contamination and toxicology, 2015
This study investigates how the feeding pattern of e(-) donors might affect the efficiency of enh... more This study investigates how the feeding pattern of e(-) donors might affect the efficiency of enhanced in situ bioremediation in TCE-contaminated aquifers. A series of lab-scale batch experiments were conducted using butyrate or hydrogen gas (H2) as e(-) donor and a TCE-dechlorinating microbial consortium dominated by Dehalococcoides spp. The results of these experiments demonstrate that butyrate is similarly efficient for TCE dechlorination whether it is injected once or in doses. Moreover, the present work indicates that the addition of butyrate in great excess cannot be avoided, since it most likely provide, even indirectly, significant part of the H2 required. Furthermore, methanogenesis appears to be the major ultimate e(-) accepting process in all experiments, regardless the e(-) donor used and the feeding pattern. Finally, the timing of injection of H2 seems to significantly affect dechlorination performance, since the injection during the early stages improves VC-to-ETH dech...
Bulletin of environmental contamination and toxicology, 2015
This work puts forth a heuristic approach for investigating compromises between quality of fit an... more This work puts forth a heuristic approach for investigating compromises between quality of fit and parameter reliability for the Monod-type kinetics employed to model microbial reductive dechlorination of trichloroethene. The methodology is demonstrated with three models of increasing fidelity and complexity. Model parameters were estimated with a stochastic global optimization algorithm, using scarce and inherently noisy experimental data from a mixed anaerobic microbial culture, which dechlorinated trichloroethene to ethene completely. Parameter reliability of each model was assessed using a Monte Carlo technique. Finally, an alternate quantity of applied interest was evaluated in order to assist with model discrimination. Results from the application of our approach suggest that the modeler should examine the implementation of conceptually simple models, even if they are a crude abstraction of reality, as they can be computationally less demanding and adequately accurate when mod...
Endocrine disrupting chemicals (EDCs) are compounds of mainly anthropogenic origin that interfere... more Endocrine disrupting chemicals (EDCs) are compounds of mainly anthropogenic origin that interfere with the endocrine system of animals and humans thus causing a series of disorders. Wastewater treatment plants are one of the major routes for transporting such chemicals to the water courses. In the context of this study, several chlorination batch tests were performed in order to assess the effectiveness of chlorination to remove bisphenol A (BPA), triclosan (TCS), nonylphenol (NP) and its ethoxylates (NP1EO and NP2EO) from secondary effluent. According to the results, an appreciable removal of NP, BPA and TCS to the order of 60-84% was observed as an effect of moderate chlorination doses. This was not the case for NP1EO and NP2EO as even at high chlorine doses, removal efficiencies were lower (37% for NP1EO and 52% for NP2EO). Removal efficiencies of NP, BPA and TCS are practically independent of contact time, although this was not the case for NP1EO and NP2EO. Based on toxicity experiments, it is anticipated that following chlorination of the target chemicals, production of more toxic metabolites is taking place. Therefore the effectiveness of chlorination to remove EDCs is questionable and more research is needed to guarantee safe wastewater reuse.
The aim of this study was to assess the feasibility of co-digesting lipids originated from domest... more The aim of this study was to assess the feasibility of co-digesting lipids originated from domestic wastewater along with sewage sludge. Three lab-scale single stage mesophilic anaerobic digesters were operated under a constant hydraulic retention time (15 days). One system (C) was fed on a daily basis with sewage sludge and served as the control system and its operation was compared with two experimental systems (E1 and E2). Both experimental systems received mixtures of sludge and lipids with different lipids content (20 % for system E1 and 60 % for system E2 on a VS basis), whereas organic loadings were 2 KgVS m-3 d-1 and 3,5 KgVS m-3 d-1 for systems E1 and E2, respectively. According to the results it can be stated that the addition of lipids to sewage sludge up to 60 % on a VS basis resulted in a significant increase of biogas production without producing any severe effects on the properties of the digested sludge. More specifically biogas production of reactor E1 was 18 % grea...
Endocrine disrupting chemicals and non-steroidal anti-inflammatory drugs are two important groups... more Endocrine disrupting chemicals and non-steroidal anti-inflammatory drugs are two important groups of emerging pollutants due to their toxicological and chemical characteristics and their persistent detection in the aquatic environment. Wastewater treatment plants are a significant pathway for their transfer to the water courses. It is well evidenced that these chemicals are only partially removed through biological treatment of wastewater and therefore being detected in secondary effluents. This work focuses on the evaluation of the efficiency of two well-established disinfection technologies (chlorination and UV irradiation) along with UV/H2O2 and powdered activated carbon (PAC) to remove these chemicals from biologically treated wastewater. Based on the results it is shown that appreciable removal efficiencies due to chlorination should be expected for most of the target compounds, whereas this was not the case for ibuprofen and ketoprofen. With the exemption of diclofenac and ketoprofen direct UV irradiation did not efficiently removed target compounds for UV doses usually applied for disinfection purposes. The application of advanced UV treatment through the addition of H2O2 although resulted in increased removal of the target compounds is not sufficient at moderate UV and H2O2 doses to achieve satisfactory removal efficiencies. PAC use resulted in sufficient removal of target compounds although high PAC doses were required for some chemicals. Comparison of Freundlich isotherms of this study with those of other studies, derived employing water samples, suggested that the water matrix along with the target compounds concentration range can significantly affect the outcome of the experiments.
Trichloroethylene (TCE), a compound classified as carcinogenic substance, is widely used in indus... more Trichloroethylene (TCE), a compound classified as carcinogenic substance, is widely used in industrial and commercial sectors. Its improper storage and/or neglectful disposal have resulted in groundwater contamination in industrialized sites all over the world. Microbial anaerobic reductive dechlorination is an important mechanism of in situ remediation of groundwater contaminated with chlorinated ethenes, since it can transform TCE to ethene by gradually disengaging three chlorine atoms. However, incomplete TCE reduction is a problem due to the accumulation of the toxic intermediates of cis-dichloroethylene (cDCE) and vinyl chloride (VC). This accumulation may be caused by interdependent factors, such as the suitability and the quantity of electron donor and the composition of the microbial community. The addition of electron donors to the subsurface (biostimulation) can significantly enhance reductive dechlorination efficiency, by stimulating the native dechlorinating population. ...
The collective literature on dechlorination performance in the presence of sulfate can be interpr... more The collective literature on dechlorination performance in the presence of sulfate can be interpreted to suggest that dechlorination at sites with elevated sulfate concentrations may be incomplete. Previous work comparing laboratory and field data concluded that the presence of sulfate in sites contaminated with trichloroethylene (TCE) might delay dechlorination but not preclude its completion. To further reconcile these conflicting reports, this work studied quantitatively the effect of sulfate on TCE biotransformation with the aid of a series of laboratory batch experiments, some up to one year-long. Specifically, the aim of the study was three-fold: to confirm whether indeed complete dechlorination is possible under sulfate-reducing conditions, to quantify the delay of dechlorination with suitable metrics, and to investigate whether this delay can be reduced by increasing the quantity of the supplied electron donor. In experiments with initial sulfate concentrations of 1.56 mM (1...
The collective literature suggests that cheese whey powder is a low cost material and an efficien... more The collective literature suggests that cheese whey powder is a low cost material and an efficient substrate to support microbial inorganic or organic pollutants removal. This study investigates the effectiveness of liquid cheese whey as an electron donor on reductive dechlorination of TCE for the replacement of butyrate, an industrial-grade chemical. Results show that liquid cheese whey can be used as an electron donor, since complete transformation of TCE to ethene was achieved with two high and low carbon-content grades. Although dechlorination rate was slower compared with a butyrate-fed experiment, cost savings may outweigh possible delays in dechlorination progress. Moreover, high donor concentrations slightly decrease the rate of reductive dechlorination. The above findings lead to the conclusion that the use of liquid whey or a combined usage of liquid/powder whey may be a viable and cost effective strategy to achieve dechlorination in the field.
Bulletin of environmental contamination and toxicology, 2015
This study investigates how the feeding pattern of e(-) donors might affect the efficiency of enh... more This study investigates how the feeding pattern of e(-) donors might affect the efficiency of enhanced in situ bioremediation in TCE-contaminated aquifers. A series of lab-scale batch experiments were conducted using butyrate or hydrogen gas (H2) as e(-) donor and a TCE-dechlorinating microbial consortium dominated by Dehalococcoides spp. The results of these experiments demonstrate that butyrate is similarly efficient for TCE dechlorination whether it is injected once or in doses. Moreover, the present work indicates that the addition of butyrate in great excess cannot be avoided, since it most likely provide, even indirectly, significant part of the H2 required. Furthermore, methanogenesis appears to be the major ultimate e(-) accepting process in all experiments, regardless the e(-) donor used and the feeding pattern. Finally, the timing of injection of H2 seems to significantly affect dechlorination performance, since the injection during the early stages improves VC-to-ETH dech...
Bulletin of environmental contamination and toxicology, 2015
This work puts forth a heuristic approach for investigating compromises between quality of fit an... more This work puts forth a heuristic approach for investigating compromises between quality of fit and parameter reliability for the Monod-type kinetics employed to model microbial reductive dechlorination of trichloroethene. The methodology is demonstrated with three models of increasing fidelity and complexity. Model parameters were estimated with a stochastic global optimization algorithm, using scarce and inherently noisy experimental data from a mixed anaerobic microbial culture, which dechlorinated trichloroethene to ethene completely. Parameter reliability of each model was assessed using a Monte Carlo technique. Finally, an alternate quantity of applied interest was evaluated in order to assist with model discrimination. Results from the application of our approach suggest that the modeler should examine the implementation of conceptually simple models, even if they are a crude abstraction of reality, as they can be computationally less demanding and adequately accurate when mod...
Endocrine disrupting chemicals (EDCs) are compounds of mainly anthropogenic origin that interfere... more Endocrine disrupting chemicals (EDCs) are compounds of mainly anthropogenic origin that interfere with the endocrine system of animals and humans thus causing a series of disorders. Wastewater treatment plants are one of the major routes for transporting such chemicals to the water courses. In the context of this study, several chlorination batch tests were performed in order to assess the effectiveness of chlorination to remove bisphenol A (BPA), triclosan (TCS), nonylphenol (NP) and its ethoxylates (NP1EO and NP2EO) from secondary effluent. According to the results, an appreciable removal of NP, BPA and TCS to the order of 60-84% was observed as an effect of moderate chlorination doses. This was not the case for NP1EO and NP2EO as even at high chlorine doses, removal efficiencies were lower (37% for NP1EO and 52% for NP2EO). Removal efficiencies of NP, BPA and TCS are practically independent of contact time, although this was not the case for NP1EO and NP2EO. Based on toxicity experiments, it is anticipated that following chlorination of the target chemicals, production of more toxic metabolites is taking place. Therefore the effectiveness of chlorination to remove EDCs is questionable and more research is needed to guarantee safe wastewater reuse.
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